AfterSales Training. Fuel/Ignition Diagnosis & Repair P21

Transcription

1 AfterSales Training Fuel/Ignition Diagnosis & Repair P21

2 Porsche AfterSales Training Student Name: Training Center Location: Instructor Name: Date: Electrical Troubleshooting Logic 1 - Do you understand how the electrical consumer is expected to operate? 2-Do you have the correct wiring diagram? 3-If the circuit contains a fuse, is the fuse okay & of the correct amperage? 4-Is there power provided to the circuit? Is the power source the correct voltage? 5-Is the ground(s) for the circuit connected? Is the connection tight & free of resistance? 6 - Is the circuit being correctly activated by a switch, relay, sensor, microswitch, etc.? 7-Are all electrical plugs connected securely with no tension, corrosion, or loose wires? Important Notice: Some of the contents of this AfterSales Training brochure was originally written by Porsche AG for its restof-world English speaking market. The electronic text and graphic files were then imported by Porsche Cars N.A, Inc. and edited for content. Some equipment and technical data listed in this publication may not be applicable for our market. Specifications are subject to change without notice. We have attempted to render the text within this publication to American English as best as we could. We reserve the right to make changes without notice Porsche Cars North America, Inc. All Rights Reserved. Reproduction or translation in whole or in part is not permitted without written authorization from publisher. AfterSales Training Publications Dr. Ing. h.c. F. Porsche AG is the owner of numerous trademarks, both registered and unregistered, including without limitation the Porsche Crest, Porsche, Boxster, Carrera, Cayenne, Cayman, Panamera, Tiptronic, VarioCam, PCM, 911, 4S, FOUR, UNCOMPROMISED. SM and the model numbers and distinctive shapes of Porsche's automobiles such as, the federally registered 911 and Boxster automobiles. The third party trademarks contained herein are the properties of their respective owners. Specifications, performance standards, options, and other elements shown are subject to change without notice. Some vehicles may be shown with non-u.s. equipment. Porsche recommends seat belt usage and observance of traffic laws at all times. Printed in the USA Part Number - PNA P Edition 9/12

3 Table of Contents Chapter Description Section Introduction i System Type Designations Engine Mechanical Intake Systems Ignition System Fuel Supply Systems Exhaust Systems Mixture Formation On-Board Diagnostics (OBD II) Additional DME Functions & Special Control Systems Conversion Charts Fuel/Ignition Diagnosis & Repair

4 Fuel/Ignition Diagnosis & Repair

5 Introduction Over the past several years, the engine management and related systems of Porsche vehicles have had to respond to ever-lower emissions standards and increasingly complex legislative requirements. While each new engine design produced more torque and horsepower and lower fuel consumption, engine management systems become increasingly efficient and complex. This has increased the amount of information that the technician must have command of and the complexity of the systems the technican must understand, exponentially. This training book attempts to organize the information and system theory of Porsche engine management in an understandable and organized manner. We hope this will make your study of Porsche engine management a successful undertaking that will improve your ability to repair and diagnose Porsche engine management systems. Viel Spass! AfterSales Training Department Fuel/Ignition Diagnosis & Repair Page i

6 Page ii Fuel/Ignition Diagnosis & Repair

7 System Type Designations Model Year Porsche System Designations Model Model Year System Designation DME 35 Pin Control Unit 911 (964) DME 55 Pin Control Unit 911 (993) DME (993) DME (996) DME (996) DME (996) DME (997) 1st Gen DME (997) 1st Gen DME 7.8_ (997) 2nd Gen. DFI EMS SDI 3.1 (Siemens) 911 (991) on EMS SDI 9 (Continental) 911 Turbo CIS 911 Turbo (964) K-Jetronic, Electronic Ignition System EZ 69 w/spark Control 911 Turbo (993) DME Turbo (996) DME Turbo (997) DME Turbo (997) DFI EMS SDI 3.1 (Siemens) 924S DME 35 Pin Control Unit 928 S LH-Jetronic - EZF 928 S LH-Jetronic - EZK 928 S4/GT LH-Jetronic - EZK DME 35 Pin Control Unit 944 S DME 55 Pin Control Unit 944 S DME 55 Pin Control Unit 944 Turbo DME 35 Pin Control Unit with KLR DME Boxster/S (986) DME Boxster/S (986) DME 7.2 Boxster/S (986) DME 7.8 Boxster/S (987) 1st Gen DME 7.8_40 Cayman/S (987) 1st Gen DME 7.8_40 Boxster (987) 2nd Gen. (2.9 liter) dme Cayman (987) 2nd Gen. (2.9 liter) on dme Boxster S (987) 2nd Gen. (3.4 liter) DFI EMS SDI 3.1 (Siemens) Cayman S (987) 2nd Gen. (3.4 liter) DFI on EMS SDI 3.1 (Siemens) Boxster/S (981) DFI on EMS SDI 9.1 (Continental) Cayenne (V6) 1st Gen DME 7.1 Cayenne S 1st Gen DME 7.1 Cayenne Turbo 1st Gen DME 7.1 Cayenne (V6) 2nd Gen. (E1) DFI MED 9.1 (Bosch) Cayenne S 2nd Gen. (E1) DFI EMS SDI 4.1 (Siemens) Cayenne Turbo 2nd Gen. (E1) DFI EMS SDI 4.1 (Siemens) Cayenne (V6) (E2) DFI on MED (Bosch) Cayenne S Hybrid (V6) (E2) DFI on MED (Bosch) (Hybrid Manager) Cayenne S (E2) DFI on EMS SDI 8.1 (Siemens) Cayenne Turbo (E2) DFI on EMS SDI 8.1 (Siemens) Fuel/Ignition Diagnosis & Repair Page 1.1

8 System Type Designations Model Model Year System Designation Panamera (V6) DFI on EMS SDI 7.1 (Siemens) Panamera S Hybrid (V6) DFI on MED (Bosch) (Hybrid Manager) Panamera S DFI on EMS SDI 6.1 (Siemens) Panamera Turbo DFI on EMS SDI 6.1 (Siemens) Carrera GT DME 7.1 x 2 (Master/Slave) Page 1.2 Fuel/Ignition Diagnosis & Repair

9 Engine Mechanical Subject Page Engine Mechanical System The Four Strokes Of The Otto Cycle Fuel/Ignition Diagnosis & Repair Page 2.1

10 Engine Mechanical The Four Strokes of the Otto (combustion) Cycle By dividing the engine management system into its basic systems, and subsystems, we can gain a better understanding of engine management as a whole, and the relationships between these systems. The engine mechanical system compresses the air and fuel mixture provided by the fuel system and the ignition system ignites the air and fuel mixture to produce torque and horsepower at the crankshaft. A solid knowledge of engine management is essential for understanding of the complex computer controlled systems utilized by Porsche today. As well as being essential for the diagnosis of system faults. Engine Mechanical System The engine mechanical system consists of the intake system, the engine mechanical (motor-block, pistons, valves, etc.) and the exhaust system. The operational principal of this system is the Otto cycle. The operation of an internal combustion engine can be understood by looking at the operation of one cylinder of the engine through an entire combustion cycle. The combustion cycle consists of two crankshaft revolutions. During each of these revolutions the piston will travel from the top of the cylinder to the bottom of the cylinder, and then from the bottom of the cylinder to the top. These movements are called strokes and there are four strokes in a combustion cycle (down, up, down, up). The valve train of the engine operates the valves in synchronization with these strokes: opening the intake valve during one stroke and the exhaust valve during another stroke. Intake (1) During the intake stroke the piston is moving down and the intake valve is open. As the piston moves down, the air and fuel mixture enters the cylinder to occupy the space vacated by the piston as it moves down. At the end of the intake stroke the piston is at the bottom of the cylinder and the intake valve closes. Compression (2) Page 2.2 Fuel/Ignition Diagnosis & Repair During the compression stroke the piston is moving up and the valves are closed. The piston movement compresses the air/fuel mixture that entered the cylinder during the intake stroke. At the top of this stroke the air/fuel mixture that filled the entire cylinder at the bottom of the intake stroke has been compressed into the combustion chamber. Compressing the mixture by the ratio of the total cylinder volume to the combustion chamber volume.

11 Engine Mechanical Power (3) During the power stroke the valves are closed and the air/fuel mixture has been ignited by the ignition system. The pressure that is generated by the burning of the air/fuel mixture pushes the piston down. This stroke creates rotational force (torque), which is transmitted to the crankshaft via the connecting rod. Exhaust (4) During the exhaust stroke, the exhaust valve is opened and the piston begins moving up and forces the by products of the combustion process out past the exhaust valve and into the exhaust system. This cycle is repeated continuously as long as the engine is supplied with air/fuel mixture and ignition spark. The valve train that controls the intake and exhaust valves operates at half crankshaft (piston) speed. So, for two revolutions of the crankshaft, the camshaft will only rotate one time and open the valves it controls (intake and exhaust) once per cycle during the appropriate stroke, intake valve(s) on the intake stroke and exhaust valve(s) on the exhaust stroke. In the other two strokes the compression and the power strokes, no valves are open. A one-cylinder engine will only have one power pulse every other crankshaft rotation, as cylinders are added, power pulses are also added. A four-cylinder engine will have two pulses per revolution and a six-cylinder engine will have three. As the number of pulses per revolution increases the smoothness and power of the engine also increases. The engine mechanical system(s) need to always be in good working order to ensure consistent complete combustion. They must always be considered when examining the over health of our complex system(s) and performing diagnostics. Notes: Fuel/Ignition Diagnosis & Repair Page 2.3

12 Engine Mechanical Page 2.4 Fuel/Ignition Diagnosis & Repair

13 Intake Systems Subject Page General Information Air Flow Through The Engine Porsche Intake Systems Variable Intake Manifold Geometry Carrera (996/997/S) Boxster/S (981) Carrera/S (991) V8 DFI Naturally Aspirated Engine V8 Turbo Engine V6 Cayenne DFI Expansion Intake Systems Hot-film Mass Air Flow Sensor Pipe Hot-film Mass Air Flow Sensor Pressure Sensor for Load Detection Electronic Throttle Valve Basic Principal of E-Throttle Throttle Valve Control Unit Throttle Valve Adaptation Accelerator Pedal Sensor Sport Button Fuel/Ignition Diagnosis & Repair Page 3.1

14 Intake Systems General Information Air Flow Through Engine This supercharging effect is therefore based on utilizing the dynamics of the air that is drawn in. The dynamic effects in the intake manifold depend not only on the geometric conditions in the intake manifold, but also on the engine speed. Ram-effect Supercharging When the vehicle is at idle, the throttle plate will close off the intake air flow path and the engine will be held to a low RPM. This will cause the pressure in the intake system (7) to drop below atmospheric pressure (6) since the engine is attempting to pull air past the closed throttle plate. As the throttle plate is opened, the pressure will rise towards atmospheric pressure, at wide-open throttle the pressure will be close to atmospheric pressure. The exhaust system directs the combustion by-products from the engine (9) to the rear of the vehicle. The pressure in the exhaust system (10) pulses positive/negative, due to the gas inertia of the exhaust flow. The exhaust gas continues to move after the exhaust valve has closed, forming a low pressure in the exhaust runner below the closed valve. Porsche Intake Systems The main components of the intake system are the air cleaner, the load detection components, the throttle valve (electronic throttle), the intake manifold and the valves. The achievable engine torque is almost proportional to the amount of fresh air in the cylinder charge. The maximum torque can therefore be increased within certain limits by compressing the air before it enters the cylinder. The gas cycle processes are not only influenced by valve timing, but also by the intake and exhaust systems. In response to the suction work performed by the pistons, the opening intake valve triggers a returning pressure wave. At the open end of the intake manifold, the pressure wave hits static ambient air, and is reflected back to the intake valve. The resultant fluctuations in pressure at the intake valve can be used to increase the fresh gas charge, thereby achieving the highest possible torque. With ram-effect supercharging, each cylinder has an individual ram tube of a specific length which is generally connected to a collecting tank. The pressure waves can spread out independently of each other in these ram tubes. The supercharging effect depends on the intake manifold geometry and the engine speed. The length and diameter of the individual ram tubes are therefore matched to the valve timing so that a pressure wave reflected at the end of the ram tube runs through to the next cylinder s open intake valve in the desired rev range, thus allowing improved cylinder charging. Long thin ram tubes have a high supercharging effect at low revs for a high torque, while short, wide ram tubes have a favorable effect on power output at high revs. Resonance Induction At a certain engine speed, the gas vibrations in the intake manifold, triggered by the periodic piston movement, produce resonance. This results in an additional increase in pressure and an additional supercharging effect. With resonance intake manifold systems, groups of cylinders with the same firing intervals are connected via short intake pipes to one resonance tank. The rev range for which the supercharging effect from the resultant resonance is required determines the length of the resonance intake pipes and the size of the resonance tank. Separation of the cylinders into two cylinder groups with two resonance intake pipes prevents overlap of the flow processes from two adjacent cylinders in the firing order. Page 3.2 Fuel/Ignition Diagnosis & Repair

15 Variable Intake Manifold Geometry Intake Systems The additional charge as a result of dynamic supercharging depends on the engine s operating point. The two systems mentioned above increase the maximum charge that can be achieved, particularly in the low rev range. To understand how resonance tuning systems work, we need to return to the Otto cycle. When the intake stroke is occurring, the intake valve is open, the piston is descending, and the air fuel charge is rushing down the intake runner. As the piston approaches the bottom of the stroke, the intake valve closes. However, the air fuel charge that is in the intake tract cannot immediately stop moving, it has mass and inertia, so it continues to move down the intake runner. An almost ideal torque curve is achieved with variable intake manifold geometry (variable intake systems) in which various adjustments are possible using flaps, for example, depending on the engine operating point: Adjustment of the ram intake pipe length Switching between various ram intake pipe lengths or different ram intake pipe diameters Switching to a different accumulator volume. Electrically or electro-pneumatically actuated flaps, for example, are used for switching the variable intake systems Tuning Flap and Double-flow Distribution Pipe With the intake valve closed, the intake tract becomes a sealed chamber, so the air fuel charge is compressed on top of the intake valve. When the inertia bleeds off, this compressed air fuel charge expands back up into the intake tract as a pressure wave. It is this pressure wave that resonant intake tuning utilizes to move air into the motor. The design of the intake manifold causes the pressure wave to arrive at a companion cylinder while its intake valve is open and force additional air fuel mixture into that cylinder. The tuning flap changes the intake geometry so that this pressure wave effect is operational for a wider RPM band. 1 - Flange to electronic throttle 2 - Partition wall of double-flow distribution pipe 3 - Distribution pipe flap 4 - Tuning flap 5 - Air distributor for left bank 6 - Air distributor for right bank The resonance intake systems in the Boxster and Boxster S (987 as of MY 2005) also have a double-flow distribution pipe. With this system, the distribution pipe flap (3) in the intermediate pipe connecting the two intake air distributors is closed in the low rev range. The distribution pipe features a partition wall running along its length (between the electronic throttle and the distribution pipe flap in the Fuel/Ignition Diagnosis & Repair Page 3.3

16 Intake Systems intermediate pipe). This means that the 6-cylinder engine behaves like two 3-cylinder engines running in parallel in the low rev range (with the distribution pipe flap closed), resulting in an improved torque characteristic in the low rpm range. There is a switchable tuning flap (4) in the perpendicular resonance pipe between the air distributors. The air oscillations in the intake system can therefore be adjusted to the respective engine speeds so as to ensure high torques even at low revs, an even torque curve and high maximum output. The tuning flap is closed in the low rev range. The tuning flap is opened at full throttle between 5,000 and 7,200 rpm. 911 Carrera (996/997/S) 911 Carrera (996/997/S) engines have a switched tuning flap between the intake-air distributors, which improves the engine charge. The tuning flap is open in the low rev range, is closed by an electro-pneumatic valve that applies vacuum to the vacuum unit at medium revs and is opened again at high revs. Picture below: On the 997 the tuning flap is closed between 2,600 and 5,100 rpm. Switching Points of the Distribution Pipe Flap on the Boxster (987) The distribution pipe flap on the Boxster is opened in the 2 rev ranges from 3,100 to 5,000 rpm and from 5,600 to 7,200 rpm. 1 - Plastic intake manifold incl. intake pipe supports 2 - Resonance chambers integrated into the intake distributor 3 - Tuning flap 4 - Throttle housing (electronic throttle) RPM - Engine speed Nm - Engine torque 0 - Flap closed 1 - Flap open 2 - Tuning flap (red) 3 - Distributor pipe flap (yellow) Page 3.4 Fuel/Ignition Diagnosis & Repair

17 Intake Systems 911 Carrera MY /3.8-liter DFI Engines electro-pneumatic switching valve installed on the resonance tube. Under load, the tuning flap is closed between approx. 3,000 and 5,500 rpm and opened at lower and higher engine speeds. Tuning Flaps in the Intake Distributors The resonance intake system of the 3.8-liter engine is distinguished from the intake system of the 3.6-liter engine by virtue of an additional, actively switchable tuning flap in the resonance distributor between the intake distributors. This resonance intake system, which can be activated in two stages, influences and utilizes air oscillations in the intake system at different engine speeds, thereby producing high torque values at low engine speeds, a uniform torque curve in the medium rev range and high maximum power at high speeds by way of the improved engine charging values generated in this manner. The pictures show the intake system of the 3.8-liter engine and the resonance tube with tuning flap. The intake systems of both engine versions are enhanced by sound volumes in the intake distributors. They attenuate disturbing resonance sounds in the higher rpm range (5,000-6,000 rpm) and make an important contribution to the harmonic, powerful sound profile at full throttle. The design principle for the resonance chambers was adopted from the 3.8-liter engine used in the previous models. The additional chambers are integrated into the lateral intake distributors and are connected to them via a perforated partition with numerous small openings which also act as Helmholtz resonators (acoustic tuners). The tuning flap (1) is actuated by a vacuum-controlled diaphragm cell (2). Activation is map-controlled by an Notes: Fuel/Ignition Diagnosis & Repair Page 3.5

18 Intake Systems Boxster/S (981) MY /3.4-liter Engines Air Routing Note! The air filter elements on the left and right can be changed from the rear luggage compartment. The maintenance interval for the air filter elements can be found in the maintenance schedules in the PIWIS information system. Due to the new routing of the intake air, the intake section has been derestricted and the volumetric efficiency of the engine at full throttle has been improved. The intake air travels from the twin branches of the air intakes (1) on the left and right side sections via the air cleaner housing (2) with the air filter elements (3) to the throttle unit (5) for the electronic throttle. The intake sound is optimised by the Helmholtz resonators on the left and right (4). Page 3.6 Fuel/Ignition Diagnosis & Repair

19 Intake Systems Intake Manifold, Pressure Sensor Intake Manifold on the Boxster (2.7 l) The intake manifold has been modified compared with the 987. Intake Manifold on the Boxster S (3.4 l) With Tuning Flap The 3.4-liter engine of the Boxster S has a tuning flap for greater volumetric efficiency and a high engine torque at low to medium rpm as well as an even torque curve. The tuning flap of the Boxster S is closed by the electro-pneumatic switching valve between 3,000 and 5,300 rpm by applying a vacuum to the diaphragm cell. 1 - Throttle housing (electronic throttle) 2 - Pressure sensor for detecting the engine load and intake air temperature 3 - Resonance chamber in the intake distributor Notes: 1 - Throttle housing (electronic throttle) 2 - Pressure sensor for detecting the engine load and intake air temperature 3 - Resonance chamber in the intake distributor 4 - Diaphragm cell and tuning flap on the air distributor (Boxster S only) Fuel/Ignition Diagnosis & Repair Page 3.7

20 Intake Systems 911 Carrera/S (991) MY /3.8-liter Engines Silencer Air Guide 1 - Two-branch air guide from the air intake on the engine cover to the air cleaner housing 2 - Sound openings at the bottom and top of the air cleaner housing 3 - Silencer (resonator) in the air cleaner housing 4 - Diaphragm cell between the intake and silencer in the air cleaner housing on both engines 5 - Flap in the air cleaner housing silencer The dual-branch (1) air guide from the engine cover to the air filter housing has optimized/derestricted this area of the intake system. Sound Opening Both engines have a silencer (resonator) in the air filter housing that is activated via a flap. Switching points of the flap on the 3.4-liter and 3.8- liter engines: The resonator is closed for the most part, it is open between 4,500 and 6,000 rpm (irrespective of button pressed or load). Air Filter Housing and Air Filter Element The mesh on the sound openings (2) allows the intake sound to travel into the engine compartment, but prevents warm air from the engine compartment from being sucked in. The flow-optimized air cleaner housing and the two air filter elements result in higher volumetric efficiency of the engine at full load. Page 3.8 Fuel/Ignition Diagnosis & Repair

21 Intake Systems Sound Symposer The 911 Carrera models (991) are equipped with the new sound symposer as standard for the first time for a more emotive driving experience. This passive sound transmission system produces an even richer and sportier engine sound in the passenger compartment and can be activated and deactivated via the standard Sport button. 1 - Sound symposer (acoustic simulator) 2 - Control flap (vacuum-controlled) 3 - Diaphragm (amplifies the vibrations) 4 - Passenger compartment inlet at the rear shelf 5 - Intake noise transmission into the passenger compartment 6 - Unfiltered air intake 7 Air filter 8 - Throttle valve (electronic throttle) 9 - Engine, intake system The sound symposer is a passive system for transmitting engine noise into the passenger compartment. In other words it does not generate an artificial engine sound, but rather amplifies the unique sporty sound of the 911 Carrera flat engines and directs it into the passenger compartment at the push of a button. The sound symposer is located within the intake tract of the engine and is installed between the throttle valve and air cleaner. It is connected with the passenger compartment out of the customer s sight via a line in the area of the rear shelf. The engine s load-dependent intake pulses cause the diaphragm integrated in the sound symposer to vibrate; the diaphragm amplifies these vibrations before they are transmitted directly into the passenger compartment as sound via the line. 2 - Control flap (vacuum-controlled) 3 - Diaphragm (amplifies the vibrations) 4 - Passenger compartment inlet at the rear shelf 6 - Unfiltered air intake 10 - Switching valves for sound symposer and silencer (resonator in the air cleaner housing) Sound Symposer Switching Strategy The sound symposer can be electropneumatically activated or deactivated via an controllable flap located upstream of it. With the standard exhaust system, the control flap is opened by pressing the Sport button. With the Sports exhaust system, the control flap is opened when the exhaust system button is pressed. Fuel/Ignition Diagnosis & Repair Page 3.9

22 Intake Systems Intake Manifold, Pressure Sensor Tuning Flap, Carrera S On the 991 vehicles, the engine load is detected downstream of the electronic throttle by the pressure sensor on the intake manifold. The derestriction of the intake system means that the intake manifold pressure at full load (throttle valve fully open, dependent on the engine speed) is approximately in the -20 mbar range relative to the ambient pressure. The 3.8-liter engine also has a tuning flap for greater volumetric efficiency and a high torque at low to medium rpm as well as an even torque curve. The tuning flap of the Carrera S is closed by the electropneumatic switching valve between 3,000 and 5,000 rpm by applying a vacuum to the diaphragm cell. 1 - Throttle housing (electronic throttle) 2 - Pressure sensor for detecting the engine load and intake air temperature 3 - Diaphragm cell and tuning flap on the air distributor (Carrera S only) 4 - Resonance chamber in the intake distributor Notes: Page 3.10 Fuel/Ignition Diagnosis & Repair

23 Intake Systems V8 DFI Naturally Aspirated Engines Variable Intake System - Cayenne/Panamera In the variable intake system used in the Cayenne and Panamera S, four switching flaps are fitted on a steel shaft for each bank and are encapsulated with silicon for a reliable sealing effect. A high torque curve is achieved, depending on the position of the intake manifold switching flap in conjunction with the optimized intake duct geometry. The chart shows the torque curve with a long intake manifold (LS - blue, 538 mm) and a short intake manifold (KS red, 284 mm). When the engine is started, the DME control unit activates the electric switching valve and a vacuum closes the variable intake system flaps in the intake manifold. As a result,the engine operates with the long intake manifold up to 4,150 rpm, thereby increasing the torque. If intake manifold switchover fails, the intake manifold remains in the short power position. The power output above 4,150 rpm is retained, but there is perceptibly less torque at low speeds. Intake Manifold in V8 Turbo Engines 1 - Electronic throttle 2 - Variable intake system 3 - Diaphragm cell for switching flaps 4 - Connecting link 5 - Shaft for switching flap for cylinder bank Shaft for switching flap for cylinder bank 2 Like the V8 variable intake system, the pressure system of the V8 turbo engines is manufactured in a plastic shell design. The pressure system comprises three shell elements, where the bottom shell is identical to the variable intake system. It is also made of plastic, for example, to ensure a low weight. The DME control unit activates an electro-pneumatic switching valve, which switches the vacuum to the diaphragm cell. The switching flaps for cylinder bank 1 and 2 are actuated synchronously via a connecting link. In the torque setting up to approx. 4,150 rpm, the long intake manifold is effective with a length of approx. 538 mm. In the power setting at an engine speed of more than approx. 4,150 rpm, the short intake manifold is effective with a length of approx. 284 mm. Fuel/Ignition Diagnosis & Repair Page 3.11

24 Intake Systems Unlike the V8 naturally aspirated engine, the switching flaps are not required since the turbo charging effect is produced by the two turbochargers. As a result, the lowloss short intake manifold lengths are effective for the entire map. For optimum efficiency, the compressed and heated air is cooled again by the charge-air coolers (upstream of the electronic throttle) in the turbo engines. Intake Manifold - Cayenne 3.6-liter V6 DFI MY 2008 The 3.6-liter V6 DFI engine uses operating sleeves instead of switching flaps for adapting the intake manifold length. These move into torque position when the engine is started and up to an engine speed of 4,200 rpm and this is apparent from the repositioning of the operating sleeves (at the front left of the intake manifold in direction of travel). The vacuum unit pulls the lever to the left (in direction of travel). The operating sleeve seals the reflection point to the power accumulator, which renders the reflection point to the torque accumulator effective. The effective ram tube length is approx. 610 mm in torque setting 1 - Electronic throttle 2 - Torque accumulator 3 - Power accumulator 4 - Electro-pneumatic switching valve 5 - Vacuum unit 6 - Operating sleeves (sealed) If the engine speed exceeds 4,200 rpm, the power position is activated by opening the operating sleeves. The operating sleeve opens the reflection point to the power accumulator, which renders the short ram tube effective with a length of approx. 235 mm. Important! If intake manifold switchover fails, the intake manifold remains in the short power position. The power output above 4,200 rpm is retained, but there is perceptibly less torque at low speeds. The chart shows the torque curve with a long intake manifold of 610 mm (blue) and a short intake manifold of 235 mm (purple). Notes: Page 3.12 Fuel/Ignition Diagnosis & Repair

25 Intake Systems Expansion Intake Systems The disadvantage of a resonance intake system, particularly for turbo engines, is the additional air heating as a result of compressing the air. This means that the fuel/air mixture in the combustion chamber cannot be ignited with optimum efficiency. For this reason, the 911 Turbo (997) uses an expansion intake manifold that is designed so that, unlike naturally aspirated engines, this effect only occurs in the higher rev range, but is neutralized at maximum power. At first glance, the expansion intake manifold looks much the same as conventional intake manifolds. It has no unusual design features such as additional resonance flaps or other moveable components. Like a traditional intake manifold, the expansion intake manifold consists of a distributor pipe, two accumulators and six individual intake pipes. The most important difference is the geometric tuning of the distributor pipe and the individual intake pipes. Operating Principle of the Expansion Intake Manifold Expansion intake systems can only be used for turbo engines. The expansion intake manifold completely turns around the resonance induction effect at high engine speeds and loads. The principle of air expansion is used instead of compression. Expansion takes place at the point where the distributor pipe goes into the intake pipes. In contrast to compression, the air is not heated but cooled. This effect results in a lower fuel/air mixture temperature in the combustion chamber, which means that the mixture can be ignited in a more efficient manner. This improves engine efficiency and ensures higher engine power and low fuel consumption with a high load and revs. The cylinders are filled with slightly less air during expansion than during compression. To compensate for this effect, the boost pressure is increased accordingly on the 911 Turbo engines. Despite a reduction in the flow cross-section in the distributor pipe of more than 65%, approx. 4% more power has been achieved with the new expansion intake manifold. Load Detection Measurement of the air mass involved in combustion is a very important factor in ensuring that the air/fuel mixture can be set accurately. The mass air flow sensor, which is located upstream of the throttle valve, measures the air mass flowing into the intake manifold and sends an electric signal on to the engine control unit. On some new systems, the intake air mass is now calculated using a pressure sensor installed at the intake manifold in conjunction with the throttle valve position and engine speed. The DME control unit determines the required fuel mass from the intake air mass and the current engine operating state. 1 - Distributor pipe 2 - Intake pipes 3 - Expansion point Fuel/Ignition Diagnosis & Repair Page 3.13

26 Intake Systems Hot-film Mass Air Flow Sensor (MAF) Operating Principle The hot-film mass air flow sensor (MAF) is installed between the air cleaner and throttle valve and detects the mass air flow drawn in by the engine. The mass air flow is actually measured inside a bypass duct, which separates some of the air flow routed through the MAF. The air flow cools an electrically heated platinum film resistor. A control circuit feeds the heating current so that the film resistor assumes a constant over temperature compared to the intake air temperature. The heating current is then a measure of the mass air flow. This measuring principle also takes the air density into account as it also determines how much heat is released into the air by the heated body. A temperature sensor is integrated as a measuring resistor in the measuring circuit of the MAF in order to determine the intake air temperature. Long-term measuring accuracy is retained even without burn-off, as was necessary with older hot-wire mass air flow sensors. Since dirt is mainly deposited on the front edge of the sensor element, the elements that are decisive for heat transfer are arranged downstream on the ceramic substrate. If the mass air flow sensor fails, the DME control unit uses a substitute mass air flow model that is stored in the engine control unit for this eventuality. MAF Versions Different mass air flow sensors are used depending on the model and model year and these are differentiated by the engine-specific nominal air mass and the air guide in the air duct. The above picture shows an old version of the hot-film mass air flow sensor (MAF 5) on the left and on the right, the newer version (MAF 5 CL) with the C-shaped air duct which was installed for the first time in the Boxster (986) from 01/2000 onwards. MAF 5 CL 1 - Air flow 2 - Sensor element 3 - Transverse bore With MAF 5 CL, air no longer flows to the sensor element (2) at a 90 angle, whereby the mechanical load due to dust particles or drops of water is reduced. A transverse bore (3) is used to compensate for air pulsations. Notes: Page 3.14 Fuel/Ignition Diagnosis & Repair

27 Intake Systems Pipe Hot-film Mass Air Flow Sensor Bypass Duct Various vehicles have a pipe hot-film mass air flow sensor adapted to the engine. With these versions, the sensor and measuring pipe are manufactured as one unit and must not be separated as these components have been matched on a flow bench. Hot-film Mass Air Flow Sensor MAF 7 All MY 2009 Boxster and Cayman models, for example, use the new hot-film mass air flow sensor MAF 7-RP (RP = Reduced Pressure Drop). This mass air flow sensor has a 5-pin connector with a trapezoidal shape and is welded to the measuring pipe. Like its predecessor (MAF 5), it too generates an analog voltage signal according to a thermal measuring principle. The intake air temperature is measured at the same time. There is a special bar to the air guide at the right of the MAF in the measuring pipe to optimize the air flow. Components: Measuring pipe Micromechanical sensor element with return-flow detection Sensor electronics with signal processing and interface Intake air temperature sensor (NTC) Advantages: Low tolerances, improved characteristic Less sensitive to water, particles and oil Compact design and reduced pressure drop Return-flow detection Flexible installation position Extremely robust and dynamic Integrated temperature compensation The flow characteristics of the bypass duct have been optimized compared to the previous MAF 5 sensor. The vacuum behind a deflection edge (1) draws the partial air flow required for metering of the air quantity into the bypass duct (2). The more inert dirt particles are left behind by this fast motion and are returned to the intake air via an elimination bore (3). This means that the dirt particles cannot falsify the measurement result and damage the sensor element. Detecting the Air Mass and Direction of Air Flow Through the Hot-film Mass Air Flow Sensor (MAF) Current hot-film mass air flow sensors detect not only the air mass and temperature, but also the direction of air flow. The mass air flow sensor is installed in the air guide between the air filter and throttle valve. 1 - Air flow 2 - Heated micromechanical sensor element with two temperature sensors 3 - Transverse bore (air pulsations) Design: The micromechanical sensor element is located in the MAF sensor s flow channel. A micromechanical measuring system with a hybrid circuit is used to evaluate the measurement data in order to detect when return flow takes place during significant air-flow pulsation. Operating Principle: A heated sensor element in the mass air flow sensor dissipates heat to the incoming air. The higher the air flow, the more heat is dissipated. The resulting temperature differential is a measure of the air mass flowing past the sensor. An electronic hybrid circuit Fuel/Ignition Diagnosis & Repair Page 3.15

28 Intake Systems evaluates this measurement data so that the air flow quantity and its direction of flow can be detected precisely. Only part of the mass air flow is detected by the sensor element. The total air mass flowing through the measuring pipe is determined by means of calibration, known as the characteristic-curve definition. Output Signal from the MAF The complete hot-film element is divided into the heating area, which is important for detecting the air mass and is heated to a constant temperature by the electronics and two temperature sensors (one upstream and one downstream of the heating element). The air mass is calculated based on the heating current. The direction of flow of the intake air can be determined by detecting the temperature difference using the temperature sensors upstream and downstream of the heating element. The plausibility of the load signal from the MAF is checked in the current DME systems. An engine speed and load-dependent map is stored in the DME control unit for this purpose. The mass air flow sensor must be checked in accordance with the guided fault finding instructions. The static sensor voltage of the MAF when the ignition is switched on (0.90 to 1.10 volts) is used as the basic check in the current systems. This graph shows the increase in air mass on a 911 Carrera 3.6- liter engine when accelerating at full throttle in 2nd gear from approx. 1,500 rpm to maximum rpm. Depending on displacement and engine type (naturally aspirated engine/turbo engine), the intake air mass when the engine is at operating temperature and no additional loads are switched on is between approx. 12 kg/h and up to > 1,000 kg/h. The intake air mass at idle speed on a 2.5-liter engine, for example, is approx. 12 kg/h and approx. 18 kg/h on a 3.8-liter engine, while the intake air mass at full throttle and maximum rpm on a 2.5-liter engine, for example, is approx. 600 kg/h and approx. 900 kg/h on a 3.8-liter engine(up to > 1,000 kg/h for larger engines or turbo engines). Notes: This graph shows the voltage signal in volts (3) from the mass air flow sensor while driving (1) and when the air mass (2) is flowing back. Page 3.16 Fuel/Ignition Diagnosis & Repair

29 Intake Systems Pressure Sensor for Load Detection Advantages of the pressure sensor: Increased power as a result of dethrottling of the intake section Greater precision with low air-flow rate Enhanced resistance to soiling Lightweight design (the pressure sensor replaces two MAF sensors) The pressure sensor for measuring the mass air flow was introduced with the Panamera. This replaces the previous hot-film mass air flow sensor (MAF). It is located at the rear of the intake manifold (1) and also helps to increase engine power by dethrottling the intake section. The integrated temperature sensor is used to measure the intake air temperature. 1 - Sensor housing 2 - Cover 3 - Pressure sensor chip 4 - O-ring 5 - Intake air temperature sensor (NTC) 6 - Capacitors 7 - Lead frame The actual intake air mass is calculated using the signal from the pressure sensor. The air mass is calculated in the DME control unit using the parameters intake manifold pressure, intake air temperature, throttle valve position and engine speed. The amount of fuel to be injected is calculated based on this load signal. This ensures that the correct fuel/air mixture is always available in the combustion chambers and any changes in the air pressure (due to changes in altitude) and outside temperature are compensated. The signals from the pressure sensor, e.g. intake manifold pressure, air mass, intake air temperature, etc., can be found under the DME actual values. The plausibility check for the pressure sensor signal is performed in the DME control unit. For this purpose, the current filtered values from the ambient pressure sensor (in the DME control unit) and intake manifold pressure sensor and boost pressure sensor (Turbo only) are compared with each other in the event of ignition ON for > 10 seconds or control unit run-on > 10 seconds, for example. Further diagnostic information is described in Guided Fault Finding. 1 - Sensor housing 2 - Intake manifold pressure 3 - Pressure sensor chip 4 - Bonded connection 5 - Ceramic substrate 6 - Glass base Fuel/Ignition Diagnosis & Repair Page 3.17

30 Intake Systems The sensor element of the micromechanical pressure sensor consists of a silicon chip, in which the pressure diaphragm has been etched. A change in pressure leads to a dilation in the diaphragm which is detected through changes in the resistance (piezo-resistive effect). The evaluation circuit (including comparison value) is integrated on the chip. Voltage Characteristic The figure below shows the voltage characteristic of the intake manifold pressure sensor as a function of the intake manifold pressure. The supply voltage of the pressure sensor = 5 volts P - Intake manifold pressure (absolute pressure in hpa) V - Signal voltage in volts Controlling the Air Charge (Electronic Throttle) The supplied air mass is the decisive factor for the engine torque output and therefore for engine power. That is why in addition to fuel proportioning, the systems that influence the cylinder charge are also particularly important. The throttle valve, which is located in the intake duct, controls the air flow taken in by the engine and therefore the cylinder charge. On conventional systems, the throttle valve is mechanically operated. An operating cable or linkage transmits the movement of the accelerator pedal to the throttle valve. The variable work angle of the throttle valve influences the opening cross-section of the intake duct and in this way controls the air flow taken in by the engine and therefore the torque output. Electronic Throttle Valve (Electronic Throttle) With electronic engine power control (electronic throttle), the DME control unit is responsible for activating the throttle valve. The throttle valve, the throttle valve drive - a DC motor - and the throttle valve angle sensor are combined together to form the throttle valve control unit. The throttle valve control unit (electronic throttle) is activated by detecting the position of the accelerator pedal using the accelerator pedal sensor. The opening of the throttle valve required for the driver request is then calculated by the engine control unit taking into consideration the current operating state of the engine and vehicle (engine speed, engine temperature, PSM, PDK, etc.) and converted into activation signals for the throttle valve drive. If faults are detected in the part of the system that determines performance, the throttle valve immediately assumes a defined position (emergency mode). The electronic throttle also enables improved mixture composition, so that the increasingly stringent requirements of emissions legislation can be met. The electronic throttle is essential in meeting all of the demands that direct fuel injection imposes on the overall system. Notes: Page 3.18 Fuel/Ignition Diagnosis & Repair

31 Intake Systems Basic Principal of E-Throttle The most significant change with electronic throttle control is the priority in the control sequence. With E--Throttle when the driver puts his/her foot down, the engine control unit: Senses the accelerator pedal position via the pedal position sensor. Opens the throttle valve via the electric motor in the throttle body. Increases the injector duration by increasing pulse width. Advances the ignition timing, the amount of torque the engine produces increases so the vehicle speed increases. The result is, the vehicle speed increases. With E-Throttle the driver becomes an input to the control system. The driver cannot open the throttle directly, instead initiates a request that the control unit open the throttle. With E-Throttle, the response between the input of the pedal sensor and the movement of the throttle valve is almost instantaneous. System Operation The E-Throttle system consists of three main components. Accelerator Pedal Position Sensor Engine Management Control Unit Throttle Valve Control Module When the driver depresses the accelerator pedal: 1. The pedal position sensor potentiometers send a pedal position signal to the engine management control unit. 2. Based on this signal, the control unit determines the desired throttle valve position. 3. The control unit sends current to the motor connected to the throttle plate, and it moves. 4. The motor moves the throttle plate until the signals from the throttle plate potentiometers indicate that the desired throttle valve position has been reached. There is the possibility of the system overriding the driver. Why and when would this be done? When the torque produced would induce unstable handling (wheel spin caused by torque excessive torque breaks wheels loose) When downshifting while decelerating and too low a gear is selected causing the wheels to break loose. The throttle is opened to reduce the engine braking effect. When the lateral acceleration is so high that the PSM cannot maintain vehicle stability if torque rises any further. When the engine is unloaded and high RPMs might damage the engine. (Over revving) In normal operation, the E-Throttle functions like a throttle cable vehicle (The throttle follows the pedal position). Intervention is only initiated when it is necessary to maintain vehicle stability or to protect the engine. The E-Throttle system eliminates the idle stabilizer. The E-Throttle system controls idle with the throttle plate. The E-Throttle also eliminates the cruise control servo and control unit. 1 - DME control unit 2 - Pedal value position (sensor) 3 - Monitoring unit for diagnosis 4 - Electronic throttle (actuator) 5 - Other input signals 6 - Other output signals Throttle Valve Control Module Self Test and Monitor The E-Throttle system performs a self- test of the throttle valve control module each time the ignition is switched on, if the time before the engine is started is longer than 10 seconds. The following items are checked: Closing spring test Opening spring test Emergency position test (where the throttle plate parks when the electric motor is not energized) Fuel/Ignition Diagnosis & Repair Page 3.19

32 Intake Systems An adaptation can also be performed with the tester. When the adaptation is performed the engine management control unit closes the throttle plate completely to determine its mechanical stop. It then remembers this position and establishes an electrical stop. Afterward the throttle is not closed beyond the electrical stop. This prevents the throttle from wearing a groove in the throttle body that the throttle would bind in. There is a wide open throttle electrical stop, however; this is not set during an adaptation, it is established by the engine control unit. The control unit can find wide open throttle by monitoring air mass. Throttle Valve Control Unit The throttle valve control unit (electronic throttle) essentially consists of the following parts: Throttle valve with reset spring Drive unit with position sensing, integrated in one housing Drive It is driven by a DC motor that is connected to the throttle shaft via a two-stage drive. The position of the throttle valve is sensed by two potentiometers that are mounted directly on the throttle shaft. This is how the engine control unit determines wide open throttle: When the throttle plate is opened the air mass should rise. The throttle is opened to the point where the air mass begins to fall. The throttle has just gone beyond wide open throttle. The wide open throttle point is just before the air mass began to fall 1 - Housing with throttle valve 2 - Throttle valve drive 3 - Housing cover with electric drive 4 - Position sensing via two potentiometers Notes: Page 3.20 Fuel/Ignition Diagnosis & Repair

33 Intake Systems The graph below shows the voltage range (5) of potentiometers 1 and 2 in the throttle valve control unit from throttle valve closed (3) to full throttle (4). The voltage of potentiometer 1 and potentiometer 2 goes in opposite directions. The sum of the two voltages must always be 5 volts. During electronic throttle adaptation, the throttle valve is closed electrically as far as the mechanical stop after approx. 35 seconds and then opened by >10%. The mechanical stop Close is re-taught during this adaptation. The mechanical operation range is 5 and voltages below 3 or above 4 are used for fault detection. 1 - Potentiometer Potentiometer Throttle valve closed 4 - Throttle valve open fully 5 - Voltage range If there is a lack of engine power, the throttle valve actual value can be used to check whether the throttle valve opens fully. The adjustment range is from 0-100%, or from 0-80 (100% and 80 = open fully), depending on the system. If one potentiometer sends an implausible signal, a substitute value is used, whereby throttle valve opening is delayed (10%/second) and the throttle valve only opens by max. 30%. Accelerator Pedal Sensor 911 Carrera/S (997) and Boxster/S (987) The new electronic pedal sensor operates without contact and is therefore wear-free. The sensors on the printed circuit board (1) are inductively activated by a metal plate, which is moved mechanically behind the printed circuit board by the pedal. The electronic pedal sensor (also called accelerator pedal module) has an accelerator pedal, a spring-loaded unit for kickdown simulation (only with Tiptronic), a printed circuit board (1) with the electronic pedal sensors 1 and 2 and an electric plug connection. If both potentiometers send implausible signals, emergency mode is activated. As a result, the electronic throttle servo motor is no longer supplied with power and spring force keeps it slightly open at the start gap. Throttle Valve Adaptation The ignition must be switched on for 1 minute and then switched off again for 10 seconds in order to adapt the electronic throttle (the accelerator pedal must not be pressed during this time). There is also a function for direct adaptation of the electronic throttle under Maintenance in the newer DME systems. This picture shows an open pedal sensor. Important! The pedal sensor must not be opened. The pedal sensor sends the input signals for the driver torque request to the DME control unit. Fuel/Ignition Diagnosis & Repair Page 3.21

34 Intake Systems Cayenne All Cayenne vehicles have a suspended accelerator pedal module in which the sliding-contact potentiometers 1 and 2 are integrated. The actual values of potentiometers 1 and 2 can be read out and a kickdown adaptation can be performed using the PIWIS Tester. 1 - Potentiometer Potentiometer Throttle valve closed 4 - Throttle valve open fully 5 - Voltage range The gray area below idle 3 and above full throttle 4 are shown. The voltages in these areas are not possible (they are mechanically inaccessible). If a voltage in these ranges is sent to the engine management control unit, a defect in the pedal position sensor is detected and a fault is indicated. Accelerator pedal module in the Cayenne 1 - Accelerator pedal 2 - Pedal sensor 3 - Spring-loaded unit for kickdown simulation (only on Tiptronic vehicles) The graph shows the voltage range (5) of pedal sensors 1 and 2 in the accelerator pedal module from throttle valve closed (3) to full throttle position (4). The voltage of potentiometer 2 is always 50% of potentiometer 1. The supply voltage for the pedal sensors is 5 volts (potentiometer 1), and 2.5 volts (potentiometer 2). Pedal position 1: approx. 0.6 V to approx. 4.0 V Pedal position 2: approx. 0.3 V to approx. 2.0 V This figure shows the integrated sliding-contact potentiometers Potentiometer 1 and Sliding contacts for potentiometer 1 and Spring-loaded unit Important! The pedal sensor must not be opened. Page 3.22 Fuel/Ignition Diagnosis & Repair

35 Intake Systems Emergency Operation and Monitoring Notes: The accelerator pedal position sensor, and the throttle valve control module; are continuously monitored by the engine control unit for electrical defects and plausibility. If a defect is detected, operation in a limited mode will be initiated. Some defects, for example; a total failure of both potentiometers in the pedal position sensor will render the vehicle inoperative. The same would be true of both potentiometers in the throttle valve control module. The system cannot operate if the position of the accelerator pedal or the throttle plate cannot be determined. Sport Button Some models feature a Sport button (often as an option). Accelerator-pedal characteristics: 1 - Pedal travel in % (driver request) 2 - Engine torque in % 3 - Characteristic in Normal mode (green) 4 - Characteristic in Sport mode (violet) Example of 911 Carrera (997) and Boxster (987) When the Sport Chrono function is activated, the accelerator-pedal characteristics become more dynamic and the rev-limiter is adjusted to a hard setting. These adjustments, along with other interventions relating to Tiptronic and Porsche Doppelkupplung (PDK) or PSM, for example, enable the driver to achieve even faster lap times during sporty driving. Fuel/Ignition Diagnosis & Repair Page 3.23

36 Intake Systems Page 3.24 Fuel/Ignition Diagnosis & Repair

37 Ignition System Subject Page Timing the Spark Electronic Digital Ignition Ignition Driver Generation of High Voltage Ignition Coil Static High-Voltage Igntion Distribution Spark Plugs Sensors Fuel/Ignition Diagnosis & Repair Page 4.1

38 Ignition System Ignition System In gasoline engines, the air/fuel mixture is ignited at the correct ignition point by the ignition system via a spark between its electrodes which in turn initiates the combustion process. Because it takes a brief amount of time for the combustion process to produce effective pressure (approximately 2 milliseconds which remains invariable as long as the mixture ratio remains fairly constant), we have to shift the ignition point of the mixture forward of top dead center to produce effective pressure at top dead center. The amount of change in this shift becomes progressively larger as engine speed increases. If we achieve effective pressure before top dead center, the gas pressure will act against the rising piston and destructive knock will occur. If we achieve effective pressure after top dead center, we lose power and torque. For best output, achieving effective pressure very close to top dead center is very important. Take a look at the Ignition angle vs. combustion chamber pressure graph, you can see the effect of early and late ignition timing on combustion chamber pressure. In addition, the electronic systems of today have done away with the breaker points and control the current flow in the primary with a transistor. These electronic systems use electronic sensors to detect crankshaft speed and position. Systems without a distributor use a second sensor on the camshaft to identify which stroke the crankshaft is on, this assures that the ignition spark is sent to the correct cylinder. Timing the Spark The goal of ignition timing control is to produce effective pressure (defined as a gas pressure in the combustion chamber high enough to move the piston) at exactly top dead center. Ignition angle vs. combustion chamber pressure graph 1. Ignition (Z a ) at correct time 2. Ignition (Z b ) too soon (ignition knock) 3. Ignition (Z c ) too late Page 4.2 Fuel/Ignition Diagnosis & Repair

39 Ignition System Electronic Digital Ignition Porsche vehicles use a digital electronic ignition system. With this system, Porsche can create, optimize and store electronic maps with the best ignition point for every load and speed combination. With distributorless ignition systems there is a coil for each spark plug. When six coils share the load that used to be handled by one coil, the amount of sparks per coil is reduced to a level where heat is not as much of a factor. In addition, electronic systems can vary the amount of dwell in relation to system voltage and engine speed creating the optimum amount of dwell for each operating condition. Graph 1 This illustration shows a electronically optimized ignition point map which is used in today's Porsche electronic digital ignition system. The map above (Graph 1) shows ignition timing on the vertical axis, load and engine speed on the horizontal axis. So, if we move to the right on the engine speed axis about half way, and then half way to the left on the load axis you end up in the middle of the map. The amount of timing advance is the height of the graph at that point. The bottom of the graph, low load and low speed, is idle, the top corner is highest load and highest speed at wide-open throttle. Dwell vs Battery Voltage and RPM Dwell In a breakerless ignition system, the time during which the electronic control unit allows current to flow through the primary winding of the coil. Notes: Fuel/Ignition Diagnosis & Repair Page 4.3

40 Ignition System Ignition Driver Task and function The DME control unit assumes the role of the distributor, in other words the calculated timing angle (based on engine speed, engine load and various correction factors) is forwarded by the processor to the ignition drivers integrated in the control unit or the Ignition coils as a function of the firing order. These ignition drivers switch current to the ignition coil s primary windings on and off. For a long time now, multi-stage power transistors (ignition drivers) have replaced the circuit breakers know as points that were previously used as a standard in an ignition system. The ignition driver also limits the primary winding current and voltage. Limiting the primary winding current restricts the energy in the ignition system to a predefined value and helps control component temperatures. Limiting the primary voltage prevents an excessive increase in the available high voltage and thus prevents damage to components. Generation of High Voltage The DME control unit switches the ignition driver on during the calculated closing time (dwell angle). The primary winding current in the ignition coil increases to its nominal value during this closing time. The primary winding current level and the primary winding inductance value of the ignition coil determines the energy created in the magnetic field. The ignition driver then interrupts the flow of current in the primary winding at the ignition point. As the magnetic field of the primary winding collapses it induces a voltage in the secondary winding of the ignition coil, ultimately initiating the combustion process via the spark plug. In the case of static high-voltage distribution with individual ignition coils, a diode in the high-voltage circuit prevents switch-on sparking. 1 - Ignition driver (with activation signal) 2 - Ignition coil 3 - Diode for suppressing switch-on sparking 4 - Spark plug 15 - Terminal designation on the ignition coil Danger! The specifications and safety instructions in the PIWIS information system, Group 2 must be observed when working on the ignition system. Ignition Coil The ignition coil produces the necessary ignition energy and generates the high voltage required to fire the spark at the ignition point. The function of an ignition coil is based on the law of induction. It has two magnetically coupled copper windings (primary and secondary) embedded in heat resistant plastic with an iron core to aid in directing and building the magnetic field. The energy created in the magnetic field of the primary winding is induced into the secondary winding as a result of the primary current being interrupted. The amount of energy created as a result of the magnetic induction principal is a function of the ratio between the number of windings in the primary and secondary circuits (turns ratio). Interrupting the primary winding current at a defined crankshaft angle (timing angle) results in the necessary ignition voltage being transferred to the spark plug were a spark is discharged, resulting in ignition of the air/fuel mixture. Page 4.4 Fuel/Ignition Diagnosis & Repair

41 Static High-voltage Ignition Distribution Ignition System With distributorless, electronic or static high-voltage distribution, each cylinder is assigned an ignition coil and ignition driver, which is activated by the DME control unit. Since there are no distributor losses, the individual ignition coils needed for this can be very small, and are connected directly to the spark plugs. 1 - Output final stage 2 - Heat sink for output final stage 3 - Electronics printed circuit board (with integrated diagnostic function and current limitation) 4 - Magnetic core 5 - Secondary winding 6 - Primary winding 7 - Electrical resistor 8 - Fastening eyelet 9 - Plug connection 10 - Spark-plug recess seal 11 - High-voltage plug to the spark plug The DME control unit activates each ignition coil in accordance with the firing order. While the ignition drivers for switching the primary current were previously integrated in the DME control unit, on the newer systems they are directly in the ignition coil. There is no restriction on the ignition adjustment range, but the system must also be synchronized with the camshaft via the signal from the Hall-effect sensor. Failure of the Hall-effect sensor can result in delayed starting behaviors. The output final stage is located directly in the ignition coil on all Cayenne vehicles and on current sports cars. Notes: Fuel/Ignition Diagnosis & Repair Page 4.5

42 Ignition System Spark Plugs The task of the spark plug is to generate a spark that is used to ignite the fuel/air mixture. If the ignition voltage is high enough, this spark is produced by the spark gap between the center electrode and ground electrode(s) becoming conductive. An abrupt discharge of the secondary ignition system occurs at this moment and a spark is created Important! The country specific change intervals for the spark plugs, plug type, heat rating and tightening torques can be found in the PIWIS information system/maintenance schedule. Note different tightening torques for new or previously installed spark plugs. Surface Gap Spark Plugs The four ground electrodes are arranged around the ceramic insulator in the surface gap spark plugs. The sparks (1) cross the surface of the insulator (4) and arc across a small gas gap to the ground electrode (2), which improves the ignition properties. The main advantage of the surface gap spark plugs is the self-cleaning effect of the insulator foot tip, since any shunts that occur between the center electrode and the ground electrode through the surface gaps, in particular during a cold start, are eliminated. Different spark plugs with corresponding change intervals are installed depending on the model. 1 - Surface arc gap 2 - Ground electrode 3 - Center electrode 4 - Insulator Platinum Spark Plugs in the Cayenne Turbo Many turbo engines use special platinum spark plugs with one ground electrode. Using a very thin center electrode reduces the voltage requirement accordingly so that a sufficient voltage reserve is guaranteed for the ignition system. 1 - Center electrode 2 - Ground electrode EA - Electrode gap a - Spark air gap with front electrode b - Spark air gap with side electrodes c - Semi-surface gap (air gap or surface gap) d - Surface gap Page 4.6 Fuel/Ignition Diagnosis & Repair

43 Ignition System Sensors General Information Sensors detect operating states (e.g. engine speed) and nominal values (e.g. accelerator-pedal position). They convert physical variables (e.g. pressure) or chemical variables (e.g. exhaust gas concentration) into electrical signals. Sensors and actuators form the interface between the vehicle with its complex functions and the DME control unit as a processing unit. Inductive Speed Sensor Inductive engine speed sensors (rod-type sensors) were mainly used to measure the engine speed and determine the crankshaft position. These consist of three important magnetic components (1, 4 and 5). The flux reversal required to generate the output voltage is supplied by the movement or rotation of the rotor. The engine speed is calculated using the time interval between the signals. The tooth interval is 6 crank angle for 60 teeth. The reference mark is needed to determine the crankshaft position. Sensors are getting smaller, faster and more accurate as their output signals directly influence the engine s power and torque, exhaust emissions, vehicle handling, safety and comfort systems. Signal processing, analogue-to-digital conversion, self-calibration functions, and embedded logic, can already be integrated in the sensor. Depending on the level of integration, the advantages of this are as follows: Less processing power is required in the control unit A standard, flexible and bus-capable interface for all sensors Direct multiple use of a sensor over the data bus Detecting of smaller measurement effects The sensor is easier to calibrate 1 - Bar magnet 2 - Sensor housing 3 - Transmission housing 4 - Soft-iron core 5 - Winding (induction coil) 6 - Rotor or pulse sender wheel with reference mark (2-teeth tooth gap) Fuel/Ignition Diagnosis & Repair Page 4.7

44 Ignition System Hall Sender This rotor on the intake camshafts of cylinder bank 1 and 2 supplies four signals per camshaft revolution (two short and two long signals). The camshaft position is determined using a Hall-effect sensor, which senses the phase sensor wheel that rotates with the camshaft. The Hall element contains a semi-conductor plate with current flowing through it. In passing, the segment of the phase sensor wheel generates a voltage on the Hall element at right angles to the current. Since this Hall voltage is in the millivolt range, the signal is already processed in the sensor and is passed on to the DME control unit as a switching signal. Together with the speed sensor at the crankshaft, the Hall senders at the camshafts are used to detect the speed and position of the crankshaft and camshaft. The signal from the Hall sender is also used to monitor the switching of the VarioCam valves. When the relevant VarioCam valve is switched, the intake camshaft of the corresponding cylinder bank moves towards intake valve opens. In other words: the Hall sender signal is also transmitted correspondingly earlier to the DME control unit. As a result, the DME control unit detects the position of the intake camshafts with respect to the crankshaft. 1 - Hall sender 2 - Rotor Notes: Page 4.8 Fuel/Ignition Diagnosis & Repair

45 Ignition System Differential Hall-effect Sensor The Cayenne V6 has a differential Hall-effect rod-type sensor on the intake and outlet camshaft. These sensors are used for optimum accuracy with high engine loads (continuous camshaft control on the intake and outlet camshaft). Other advantages include a comparatively larger air gap and efficient temperature compensation. Differential DFI Hall-effect Sensor on Vehicles With Auto Start Stop System A new Hall sender is used in the DFI engines with Auto Start Stop system for determination of the engine speed instead of the previous inductive pick-up. In addition to detecting the engine speed and reference mark, the multiple Hall-effect sensor also detects the direction of rotation of the engine. This function means that the engine starting operation is very fast for the Auto Start Stop function. The speed sensor has three integrated Hall-effect sensors (A - B - C). Only one rotor with 60-2 teeth is needed on the crankshaft to generate the corresponding signal. On the Panamera, the speed sensor is installed on the left behind the engine at the bottom of the transmission bell housing when viewed in direction of travel. The Hall-effect sensor (a) shown is installed in the Cayenne V6 Points to note: S1 and S2 are two separate Hall elements used to strengthen the signal 7 Two-strip orifice plate Function The sensor calculates two signal channels from three Hall signals. Two signal channels are generated based on the Hall technology in one sensor with three Hall elements (A, B and C): Channel 1 = Engine speed channel (Hall sender A - B) Channel 2 = Direction of rotation channel (Hall sender B - C) Fuel/Ignition Diagnosis & Repair Page 4.9

46 Ignition System The sensor switches to low when the speed channel passes through the zero line. The offset between the tooth center and falling edge in the signal is constant and can be adapted in the DME software. Detection of the direction of rotation takes place on the basis of the phase displacement between the speed channel and direction of rotation channel. Differential Hall Sensor Signal The crankshaft position and the direction of rotation are detected from the signals for channel 1 and 2. Channel 1 = Speed channel (Hall sender A - B) Channel 2 = Direction of rotation channel (Hall sender B - C) Direction of rotation forward (4). Channel 2 leads channel 1, this creates the signal (3). 1 - Sensor 2 - Rotor 3 - Signal 4 - Direction of rotation forward (upper figure) 5 - Direction of rotation backward (lower figure) Direction of rotation backward (5). Channel 1 leads channel 2, this creates the signal (3). Page 4.10 Fuel/Ignition Diagnosis & Repair

47 Fuel Supply Systems Subject Page General Information Returnless Fuel System Fuel Low-Pressure Side Electric Fuel Pump Fuel Tank Sports Car RF System Cayenne Fuel Tank Panamera Fuel Tank Fuel Tank Sports Cars (9x1) Intake Manifold Injection (MPI) EV6 Fuel Injectors Fuel High-Pressure Side Flow Control Valve High-Pressure Injector DFI High-Pressure Pump Fuel Injectors Sports Cars (9x1) Fuel High Pressure Adaptation Fuel Tank Ventilation System On-Board Vaporation Recovery (ORVR) Cayenne and Panamera (LDP) Tank Leakage Monitor Fuel Tank Leak Test Sports Cars (9x7) Tank Ventilation Sports Cars (9x1) NVLD Module Fuel/Ignition Diagnosis & Repair Page 5.1

48 Fuel Supply Systems General Information The fuel supply system has the task of always supplying the required quantity of fuel to the engine under all operating conditions. The fuel is pumped to the fuel rail or high pressure fuel pump by the electric fuel pump in the fuel tank via the fuel filter and the fuel pressure regulator. The fuel injectors installed on the fuel rail are activated by the DME control unit in order to inject the quantity of fuel required for the respective operating condition. The following chapter describes the basic principles of the fuel supply system together with the different fuel lowpressure systems as well as the points to note about the fuel high-pressure side in DFI engines. Returnless Fuel System (RF) On current vehicles, the fuel pressure regulator and the fuel filter are integrated in the fuel tank. Excess fuel pumped by the electric fuel pump therefore reenters the fuel tank directly by means of the pressure regulator. This makes the fuel return line from the fuel distributor in the engine compartment to the fuel tank superfluous (RF returnless fuel). Another advantage is that no fuel heated in the engine compartment flows back into the fuel tank, therefore increasing the fuel temperature there. This leads to a further reduction in hydrocarbon (HC) emissions in the fuel tank and helps relieves tank ventilation. Only the fuel quantity injected by the fuel injectors is pumped to the fuel distributor in the engine compartment (4). The pressure can be measured at the relevant connection (1) and in accordance with the PIWIS information system. Fuel Low-Pressure Side The fuel low-pressure system includes the components from the fuel tank to the fuel injectors on MPI engines (intake manifold injection), or to the high-pressure pump on DFI engines. Compared to MPI engines with a fuel pressure of approx. 58 psi (4 bar), the fuel pressure on the low-pressure side of DFI engines was raised to approx. 72 psi (5 bar) or psi (5.5 bar). The pressure regulator in the fuel tank keeps this pressure constant or regulates it as required. The fuel temperature on the low-pressure side on DFI engines is calculated upstream of the high-pressure pump by a temperature model in the DME control unit. The following information is recorded: outside temperature, temperature of the flow control valve, operating duration, load point, tank filling level, idle period prior to vehicle start. Page 5.2 Fuel/Ignition Diagnosis & Repair

49 Fuel Supply Systems Electric Fuel Pump The fuel pump continuously pumps the fuel out of the fuel tank to the engine through the fuel filter. To ensure that there is enough fuel at the intake openings of the fuel pump even during strong lateral acceleration, the fuel pump is located in a pump chamber, which is filled by filling pumps or sucking jet pumps. Control Unit for Fuel Pump in DFI Sports Cars (9x7 & 9x1) To ensure that pressure builds up quickly when starting the engine, the electric fuel pump comes on briefly as soon as the ignition is switched on. An integrated check valve decouples the fuel system from the fuel tank by preventing return flow of fuel. At the same time, the pressure in the system is thus maintained for a certain time after the fuel pump has been switched off, thereby preventing vapor bubbles from forming at increased fuel temperatures. Electronic pilot control of the delivery rate can cause the fuel pressure to deviate slightly for a brief period, e.g. during extreme load changes when the vehicle is driven. In earlier systems, the electric fuel pump(s) was (were) primarily activated by relays. The following pages describe how the fuel pump is activated by a special control unit. On these vehicles, the current consumption of the fuel pump is varied in the range between approx. 6 and 14 A. Depending on fuel consumption, activation is continuously increased up to the maximum delivery rate of the electric fuel pump. The control unit is installed at the right-hand side of the plenum panel. Important! The fuel pump is switched off on all vehicles and models if an airbag is triggered. For 9x1 vehicles the control unit for electric fuel pump flow control (2) is installed under the battery tray (3). At idle speed, the fuel pump is activated with minimal voltage (> 8 V). The fuel pump runs for approx. 3 seconds when the ignition is switched on. When the engine is started and depending on the engine-start temperature, activation takes place for approx. 5 seconds at high voltage to achieve the maximum delivery rate. Afterwards, activation depends on the fuel consumption. Fuel/Ignition Diagnosis & Repair Page 5.3

50 Fuel Supply Systems Control Unit for Electric Fuel Pump on the Panamera (MY 2010-on)/Cayenne (MY 2011-on) Fuel Pump on the Panamera (MY 2010-on)/ Cayenne (MY 2011-on) The pump motor in these vehicles is a 3-phase synchronous motor without position feedback and without a sensor. The speed of the fuel pump and thus the delivery rate, is therefore controlled by the frequency of the created signal. To prevent an overload of the pump motor, the phase current in the three lines is limited by the control unit. Control: In the DFI systems on all Panamera and Cayenne DFI vehicles from MY 2011 onwards, the electric fuel pump is activated continuously by a special control unit, which is installed close to the fuel tank. The DME control unit sends a PWM control signal to the control unit to control the speed of the electric fuel pump and thus the required delivery rate. This bi-directional PWM interface is also used for diagnosis of the control unit for the electric fuel pump. The control unit is powered by a fuse. Terminal 31 ensures the connection to vehicle ground. 3-phase voltage goes from the control unit to the variable-speed fuel pump. As soon as the DME control unit switches to Sleep mode, it is woken again when the driver's door is opened and the electric fuel pump is then operated with a significantly reduced speed for a period of 2 seconds. The electric fuel pump cannot be activated as long as the DME is now active (without ignition on). After the DME has switched back to Sleep mode again, this process can take place a maximum of three times without the ignition being switched on. This limit is designed to protect vehicle electrical system management. Door contact activation can be activated again up to three times with ignition On/Off. In contrast to reduced door contact activation, the electric fuel pump is activated at maximum speed for 1 second when the ignition is switched on. This ensures rapid pressure build-up when the engine is started. Note! This fuel pump must be operated only with the control unit. In the Bosch DFI system on the Cayenne V6 from MY 2011 onwards and on the Cayenne Hybrid, the delivery rate can be reduced to such an extent that the fuel pressure falls from approx psi (5.7 bar) to approx psi (3 bar), depending on the fuel requirement. These vehicles have an additional pressure sensor for fuel low pressure in the engine compartment (upstream of the high-pressure pump). Page 5.4 Fuel/Ignition Diagnosis & Repair

51 Fuel Supply Systems Fuel Tank Different types of fuel tanks are used on the various Porsche models. These fuel tanks are described on the following pages. The fuel tank contains the fuel-level sensor, the fuel pump and in the current RF systems, also the fuel filter (lifetime filter) and the fuel pressure regulator. Sucking jet pumps have no moving parts. They work according to the Venturi principle. The driving force is a propulsion jet, which is diverted from the fuel pump and guided through the sucking jet pump. The propulsion jet sucks an additional volume flow through the intake opening on the sucking jet pump. The fuel pump is specifically designed to also supply fuel to the sucking jet pumps that are used. Sports Cars (9x7) Sports Car RF System (996/997 Carrera 4) So-called saddle tanks are installed in these vehicles. The electric fuel pump (1, installed in the pump chamber) pumps the fuel through the fuel filter (2) to the pressure regulator (3), which sets the required value. Two sucking jet pumps (1A) pump the fuel out of the tank pockets on the left and right into the higher pump chamber, (4) is the fuel out flow line. Note! During normal refueling some fuel as it enters the tank is directed at the fuel pump chamber to ensure that it is filled to allow the sucking jet pumps to function in the event the tank is completely emptied and is not fueled beyond the level of the pump chamber. 1 Fuel pump (for building up fuel pressure) 1A Sucking jet pump (for filling the pump chamber) 2 Fuel filter (lasts for the service life of the vehicle) 3 Fuel pressure regulator MPI: approx. 55 psi (3.8 bar), DFI: approx psi (5.0 bar) 4 Fuel line out flow (MPI to fuel injectors or DFI to highpressure fuel pump) In this version, the fuel-level sensor does not reach into the fuel pockets. If the amount of fuel in the tank is less than approx gal. (20 liters), the remaining fuel quantity is therefore calculated by the DME based on the fuel consumption. If a vehicle is not refuelled fully after disconnecting the battery, the available fuel quantity below 5.28 gal. (20 liters) cannot therefore be displayed as a result of memory loss. Notes: Fuel/Ignition Diagnosis & Repair Page 5.5

52 Fuel Supply Systems Fuel Tank in the Cayenne (MY ) Cayenne vehicles from MY have a returnless fuel system (RF) with 2 electric fuel pumps. These are located in the two tank pockets on the left and right. The fuel pumps are each supplied by one sucking jet pump whose hoses are routed diagonally and which helps itself to fuel from the other half of the tank. Two fuel level sensors are installed in the fuel tank for measuring the fuel level. 1 - Fuel tank filler neck 2 - Fuel pump unit in right side of tank 3 - Fuel pump unit in left side of tank 4 - Sucking jet pump for left fuel pump 5 - Sucking jet pump for right fuel pump 6 - Fuel filter (lifetime filter) 7 - Fuel pressure regulator 8 - Fuel pressure (MPI: approx. 58 psi/4 bar), (DFI low-pressure side: approx. 80 psi/5.5 bar) 9 - Fuel high-pressure pump, DFI with flow control valve 10 - Fuel injectors (cylinders 1 to 6 and 1 to 8) Up to model year 2007, the left fuel pump is the main pump. The left fuel pump is always activated by the DME control unit, while the right fuel pump is only activated as required in accordance with the following criteria: When starting the engine: cold starting - 2 sec. run-on; warm starting - 5 sec. run-on Fuel consumption: > 50 l/h - on; < 45 l/h - off Fuel level in the tank: < 10 l - on; > 15 l off On Cayenne DFI engines from MY 2008 to 2010, the fuel pumps are activated in accordance with the level of fuel in the tank. 1 - Left fuel pump 2 - Sucking jet pump for left fuel pump 3 - Left fuel-level sensor 4 - Right fuel pump 5 - Sucking jet pump for right fuel pump 6 - Right fuel-level sensor 7 - Fuel filter 8 - Fuel pressure regulator (approx. 4 bar) 9 - Fuel pressure line to engine 10 - Degassing tank (for the vent lines 13 and 14) 11 - to the active carbon filter 12 - from the active carbon filter to the tank vent valve in the engine compartment 13 - Operation vent valves (4 x with rollover valve) 14 - Tank vent (with filling level limiter) If there is more than 16 gal. (60 liters) of fuel in the tank, the right fuel pump is the main pump and the left pump is activated in accordance with the above criteria. If there is less than 16 gal. (60 liters) of fuel in the tank, the left fuel pump is the main pump and the right pump is activated in accordance with the above criteria. Page 5.6 Fuel/Ignition Diagnosis & Repair

53 Fuel Supply Systems Fuel Tank in the Cayenne (as of MY 2011) 1 - Line to high-pressure pump 2 - Low-pressure line 3 - Fuel filter 4 - Line to auxiliary heater 5 - Adapter for reducing the tank filling quantity 6 - Rollover valve 7 - Fuel pressure regulator (approx. 5.5 bar) 8 - Suction jet pumps GL - Fuel level sensor, left 10 - Fuel-level sensor, right 11 - Electric fuel pump (3-phase) 12 - Pump filter As of model year 2011, only one demand-controlled fuel pump is installed in the right half of the fuel tank and its pump chamber is filled via a total of three sucking jet pumps. On Cayenne vehicles from MY 2011 onwards and on the Panamera, the DME control unit controls the speed of this 3-phase fuel pump and thus the required delivery rate, as already described, by sending a PWM control signal to the control unit for the electric fuel pump. Fuel Tank in the Panamera In order to make optimum use of the available space, the Panamera is equipped with a saddle step fuel tank with a capacity of 26.4 or 21 Gal. (100 or 80 liters. Three fuel-level sensors are installed in the fuel tank to measure the fuel level. The carbon canister is located behind the fuel tank. On Cayenne and Panamera models, a leakage diagnosis pump (LDP) is used for checking the fuel tank for leaks. This pump is installed directly at the fresh-air connection of the active carbon filter. 1 - Left-hand tank chamber 2 - Right-hand tank chamber 3 - Control unit for electric fuel pump 4 - Electric fuel pump (demandcontrolled) 5 - Fuel filter (lifetime filter) 6 - Fuel pressure regulator (approx. 80 psi/5.5 bar) 7 - Degassing tank 8 - Line from degassing tank to active extraction system 9 - Fuel level sensor, center 10 - Fuel level sensor, right 11 - Fuel level sensor, left 12 - Sucking jet pump, left (0.5 mm, 80 psi/5.5 bar) delivers to right-hand 13 - Sucking jet pump, right (0.5 mm, 5.5 bar) fills the pump chamber 14 - Sucking jet pump for filling the electric fuel pump (to approx. 29 psi/2 bar) 15 - to flow control valve at the fuel highpressure pump 16 - Active extraction (0.3 mm) from the degassing tank 17 - Signal from left and center fuel-level sensors 18 - Signal from fuel-level sensor, right Fuel/Ignition Diagnosis & Repair Page 5.7

54 Fuel Supply Systems Fuel Tank Sports Cars (9x1) The Sports Cars (9x1) series feature a returnless fuel system. On the low-pressure side, the electric fuel pump installed in the swirl pot delivers the fuel to the 3-piston high-pressure pump via the fuel filter and fuel pressure regulator (approx psi/ 5 bar). Intake Manifold Injection (MPI) For model year 2011, only the Boxster/Cayman 2.9-liter engine and the GT3 as well as the GT2 RS still feature intake manifold injection or MPI (Multi Point Injection). The pressure in the injection systems is approx. 58 psi (4 bar) on all vehicles. With intake manifold injection, the fuel injector injects the pressurized fuel earlier into the intake duct upstream of the intake valves, which are still closed. During the intake process, the air/fuel mixture is drawn through the open intake valve into the cylinder. The fuel injectors are activated by output-stage drivers located in the DME control unit using the signal calculated by the engine management system. A fuel quantity, which is adapted exactly to the engine s current fuel requirement, can therefore be measured out. 1 - Tank filler neck 2 - Surge flap 3 - Swirl pot with electric fuel pump 4 - Fuel filter with fuel pressure regulator 5 - Fuel-level sensor 6 - Fill-level control valve 7 - Control unit for electric fuel pump 8 - Electric lines 9 - Low-pressure fuel line (approx psi/5 bar) to highpressure pump 10 - Engine 11 - Tank ventilation to carbon canister Fuel injectors have different properties, e.g. design and injection volume, which are adapted to suit the relevant engine. Notes: Page 5.8 Fuel/Ignition Diagnosis & Repair

55 Fuel Supply Systems Fuel Injectors EV6 Fuel Injectors Micro-electroplating was used to improve the spray pattern and reduce the tolerances. EV12 Fuel Injectors EV12 fuel injectors, which also have four spray holes, were used for the Cayenne V6 MPI engines. The main differences between these fuel injectors and the EV6 fuel injectors, for example, are as follows: One fuel injector that was frequently used for MPI engines in sports cars and in the Cayenne was the EV6 fuel injector with its engine-specific design, injection jet, injection position and injection volume. Different EV6 fuel injectors with four spray holes were used for the Cayenne V8 MPI engines. The injection volume of the fuel injectors is different: Cayenne S: max. 210 g/min Cayenne Turbo: max. 349 g/min EV14 Fuel Injectors Figure A Figure B Figure A - Installation position of the EV12 in the cylinder head. Figure B Longer spray tube (reaching into the intake duct) 2 - Valve seat moved forward Even the EV14 fuel injectors from Bosch, which are used for 2.9-liter engines with intake manifold injection, are enhanced versions of the EV6. These fuel injectors have eight very fine discharge holes at the injector tip. Fuel/Ignition Diagnosis & Repair Page 5.9

56 Fuel Supply Systems Fuel High-Pressure Side of DFI Engines The DFI high-pressure side comprises the following components: The high-pressure pump driven by the camshaft The flow control valve on the high-pressure pump The fuel rail(s) with the supply lines The pressure sensor for high pressure The pressure control valve The fuel injectors Danger! The fuel pump and fuel distributor line are made of stainless steel so that the various-quality fuels available worldwide can be used (ethanol causes corrosion). The fuel pressure in the fuel rails (4) is approximately 580 psi (40 bar) at idle speed and up to 1740 PSI (120 bar) at full throttle. The high-pressure rails have different volumes depending on the engine and also act as a pressure accumulator. DFI Flat (Boxer) Engines Fuel routing on the high-pressure side is explained here using DFI flat engines as an example. 3 - Fuel injector 4 - Fuel rail 6 - Pressure sensor On the high-pressure rails, the injectors (3) for banks 1 and 2 are secured to the cylinder head. The fuel is injected into the combustion chamber by the high-pressure injectors activated by the DME. The pressure is monitored by the pressure sensor (6) installed on the rail and controlled by the flow control valve at the high-pressure pump. The fuel pressure sensor (6) sends a voltage signal (see graph) to the DME control unit. It has an operating range of 0 to 2465 psi (170 bar). If the sensor fails, the DME control unit sends a fixed value to the flow control valve. The high-pressure pump also has an integrated pressure control valve, which diverts any excess pressure of over approx psi (140 bar) into the low-pressure system. The electric fuel pump in the fuel tank delivers the fuel low pressure (1) to the high-pressure pump (2) via the flow control valve (7). The high-pressure pump driven by the camshaft sends the fuel high pressure to the fuel rails (4) on the left and right cylinder bank and on to the injectors (5) via the connecting lines (3). The pressure sensor (6) is located on the right fuel rail. High-Pressure Pump in DFI Flat (Boxer) Engines The fuel high-pressure pump supplies the high pressure of up to 1740 psi (120 bar) which is required for fuel injection. It is demand-controlled and adapts the fuel quantity and the fuel high pressure according to the engine s fuel requirement using a flow control valve at the inlet of the high-pressure pump. Page 5.10 Fuel/Ignition Diagnosis & Repair

57 Fuel Supply Systems Different types of high-pressure pumps are used in the various models: A 3-piston high-pressure pump is used in the DFI flat engines as well as in the V8 naturally aspirated engines and the V6 naturally aspirated engine in the Panamera. The 911 Turbo DFI engine has a 6-piston high-pressure pump similar to that used in the V8 Turbo DFI engines. 1 - Low-pressure side (input) 2 - To the high-pressure rail 3 - Pressure control (connection to the high-pressure side) 4 - Flow control valve 5 - Pressure relief and bypass valve 6 - Intake valve 7 - Outlet valve 8 - Pump piston 9 - Metal bellows 1 - Flow control valve 2 - Temperature compensator 3 - Drive of the three-piston high-pressure pump via the exhaust camshaft 4 - Low-pressure line 5 - High-pressure line The high-pressure pump is driven by the exhaust camshaft of cylinder bank 1. It is supplied with an admission pressure of approx psi/5.0 bar (80 psi/5.5 bar on the V8). The following components are integrated into the high-pressure pump: Flow control valve with pressure-reducing function for the fuel highpressure side (1) Pressure control valve Bypass valve A temperature compensator on the oil side (2) A fuel strainer on the intake side with a mesh width of approx. 50 µm The fuel is sucked in from the low-pressure side (approx psi (5.0 bar) or 80 psi (5.5 bar) on the V8) by the pump pistons via the flow control valve and the intake valves. The pistons pump the fuel into the high-pressure system via the exhaust valves. The pressure relief and bypass valve has two functions. It protects the system against excessively high pressure and relieves the pressure from the high-pressure side when the engine is switched off. Flow Control Valve The flow control valve is an electric control valve and is located on the intake side (low-pressure side) of the highpressure pump. When the vehicle is driven from idle speed to full throttle, the DME control unit activates the flow control valve with a PWM signal of between 5 % and 95 %. The fuel pressure is therefore maintained at between 580 psi (40 bar) and 1740 (120 bar) using a map. When the engine is switched off, the fuel high pressure is reduced by an integrated pressure-reducing valve. The fuel pressure sensor monitors the fuel pressure. If the control valve fails, the DME control unit goes into emergency mode, whereby the engine can still operate in a limited way with low pressure. In this case, the bypass valve in the pump opens and provides a direct route from the lowpressure side to the high-pressure side. The bypass valve is also activated for filling the empty fuel rail on new engines or following repairs in order to reduce starting times. Fuel/Ignition Diagnosis & Repair Page 5.11

58 Fuel Supply Systems High-Pressure Injector The electromagnetically operated injectors are located on the intake side in the cylinder head. The injectors in all DFI engines are designed specifically to suit the relevant fuel requirement of the engine. The engine-specific injectors can be identified by their part numbers and by a color marking. The basic structure of the injectors is the same. Activation of Continental DFI Voltage Booster (DC/DC converter) To reduce the amount of heat produced by the DC/DC converter, two fuel injectors are connected to a highvoltage driver (3). Each fuel injector is connected separately to the timed ground (5). O E K D T O O-ring on hydraulic connection E Electrical connection K Corrosion protection (external) D Spacer ring T Teflon sealing ring (to combustion chamber) To open an injector on the Continental DFI systems, the activation voltage is briefly raised to up to 75 V in accordance with the firing order by means of a voltage booster in the DME control unit. 1 - Battery voltage 2 - Voltage converter (booster) from DC 12 V to DC 75 V 3 - High-voltage side up to 75 V, 2 fuel injectors to one voltage converter 4 - Fuel injector 5 - Timed ground (for the respective cylinder) 6 - Transistor driver (ground for the respective cylinder) The injection time is controlled with the ground pulse via the respective transistor/driver (6). The red line in the following diagram shows the voltage curve when the injector is activated. A short voltage pulse of 75 volts is only needed to lift the injection needle. The holding voltage is then considerably reduced. The control unit housing close to these voltage boosters can be heated to more than 248 F. (120 C.) in parts. The heat is dissipated via the aluminum cover. Page 5.12 Fuel/Ignition Diagnosis & Repair

59 Example of V8 turbo engines: Fuel Supply Systems Approx. 7.8 mg of fuel is injected per stroke at a fuel pressure of 580 PSI (40 bar) and an injection time of 0.6 ms. Approx. 107 mg of fuel is injected per stroke at a fuel pressure of 1740 psi (120 bar) and an injection time of 6.1 ms. The injector needle is raised by approx. 50 µm as a result of activation. Following activation, it injects the fuel directly into the combustion chamber at a pressure of 580 to 1740 psi (40 to 120 bar). The characteristic drop diameter is approx. 30 µm. 1 - Boost time with activated battery voltage. 2 - Time required to maintain peak value and increase voltage to 75 volts in order to open the fuel injector. 3 - Short fall time, reduction of energy stored in the solenoid valve. 4 - Holding phase, constant current to keep the fuel injector open. 5 - Injection time 6 - Injector needle raised 7 - Time (microseconds) 8 - Current (amperes) 9 - Voltage (volts) 10 - Needle lift (%) In addition to the amount of fuel injected and the injection time, the shape and alignment of the fuel jet is also important here. The illustrations below show the injector in a V8 DFI engine The fuel quantity depends on the fuel pressure and the injection time: Example of V8 naturally aspirated engine: Approx. 5.5 mg of fuel is injected per stroke at a fuel pressure of 580 psi (40 bar) and an injection time of 0.6 ms. Approx. 67 mg of fuel is injected per stroke at a fuel pressure of 1740 psi (120 bar) and an injection time of 5.8 ms. 1 - Spray angle: taper angle of the fuel jet, approx. 69 on the naturally aspirated engine, approx. 68 on the turbo engine 2 - Bend angle: distance between the injection jet and the axis of the fuel injector; approx. 8.5 on the naturally aspirated engine, approx. 7.5 on the turbo engine. Notes: Fuel/Ignition Diagnosis & Repair Page 5.13

60 Fuel Supply Systems DFI V8 Engines Retainers for Fuel Injectors The central high-pressure rail in V8 engines is located in the engine s inner V. From here, the fuel is supplied via individual lines to the fuel injectors of cylinders 1 to 8. The volume of the high-pressure rail is adapted according to the amount of fuel the engine needs (100 ccm for the V8 naturally aspirated engine, 150 ccm for the V8 Turbo). The four retainers for securing two injectors ensure the following: Installation as a pre-assembled unit with injectors fitted Twist-lock protection for screwing on fuel lines Exact installation position for aligning the fuel jet in the combustion chamber Correct preloading of the fuel injectors in the cylinder head Vibration damper for reducing the transmission of vibrations/accelerated rocking from the cylinder head to the injectors 1 - Fuel high-pressure pump (3 or 6 pistons, depending on the engine) with flow control valve, pressure control valve and temperature compensator 2 - High-pressure line 3 - Fuel rail (engine-specific) 4 - Fuel pressure sensor 5 - Fuel line (to the fuel injector for cylinder 1) 6 - Fuel injector (engine-specific) 7 - Retainers for two fuel injectors The V6 engine in the Panamera is a shortened version of the V8 DFI engine. The fuel high-pressure system is comparable to that of the V8 naturally aspirated engines apart from the fuel rail and 2 injector retainers. Page 5.14 Fuel/Ignition Diagnosis & Repair

61 Fuel Supply Systems DFI High-Pressure Pump - V8 and Panamera V6 DFI High-Pressure Pump - V8 Turbo The high-pressure pump (HD) used in the Cayenne and Panamera Turbo is a six piston pump with a maximum delivery rate of approx. 245 liters/h at 1740 psi (120 bar). The following components are integrated into the high-pressure pump: A 3-piston high-pressure pump similar to the pump used in DFI flat engines is used in the V8 naturally aspirated engines and the V6 naturally aspirated engine in the Panamera (see section on DFI flat engines). The fuel low pressure has been raised from 72.5 psi (5.0) bar to approx. 80 psi (5.5 bar) compared with the DFI flat engines. Flow control valve (1) with pressure-reducing function for the fuel high-pressure side, pressure control valve, bypass valve, two temperature compensators (2) on the oil side and a fuel strainer on the intake side with a mesh size of approx. 50 microns. The flow control valve, pressure control valve, bypass valve, one temperature compensator on the oil side and one fuel strainer on the intake side are all integrated into the high-pressure pump. Notes: Fuel/Ignition Diagnosis & Repair Page 5.15

62 Fuel Supply Systems DFI Cayenne 3.6-liter V6 Engine The injectors for both cylinder banks are on the intake side of the cylinder head. This arrangement allows the injectors for cylinders 1, 3 and 5 to run through the intake port on the cylinder head. Consequently, the fuel injectors of cylinder bank 1 are longer than those of cylinder bank 2. Since the injectors are inserted from the same side for both cylinder banks, the piston recesses of cylinder bank 1 and 2 must be moulded differently so that the injected fuel is whirled around and mixed perfectly with the air that is drawn in. This is necessary because the fuel injectors and intake valves on both cylinder banks are arranged at different angles. The intake system is designed so that the long and short channels have similar flow characteristics. In order to compensate the influence of the fuel injectors on the flow characteristics in the intake port, the valve spacing for all cylinders was increased from 34.5 to 36.5 mm in model year This prevents the injectors from deflecting the flow when filling the cylinders. 1 - High-pressure pump with flow control valve 2 - Transfer line 3 - Rail for cylinder 1, 3, Rail for cylinder 2, 4, Long injector (cylinder 1, 3, 5) 6 - Short injector (cylinder 2, 4, 6) 1, 3, 5 - Fuel injectors at high-pressure rail, cylinder bank 1 2, 4, 6 - Fuel injectors at high-pressure rail, cylinder bank Low pressure (approx. 5.5 bar from fuel tank) 8 - Camshaft 9 - Fuel high-pressure pump (single-piston) 10 - Flow control valve (for fuel high pressure) 11 - High-pressure line 12 - Pressure control valve (max psi/120 bar) 13 - Fuel pressure sensor Page 5.16 Fuel/Ignition Diagnosis & Repair

63 Fuel Supply Systems DFI High-Pressure Pump - Cayenne 3.6-liter V6 Engine The single-piston high-pressure pump used in the Porsche Cayenne V6 engine is located at the cylinder head and is driven by the timing chain via a double-cam gear wheel by the intake camshaft. The double-cam gear wheel uses a roller to actuate the pump piston, which creates the fuel high pressure in the pump. Slight variations in pressure can occur on the low-pressure side while measuring fuel pressure at idle speed due to the single-piston highpressure pump. 1 - Low pressure 2 - Pressure control valve 3 - High pressure 4 - Pump piston 5 - Flow control valve 6 - Pressure sensor for fuel low pressure 1 Fuel high-pressure pump with flow control valve 2 Fuel pressure sensor High-Pressure Pump - Cayenne S Hybrid 3.0-liter Supercharged Engine The single-piston high-pressure pump in the V6 supercharged engine in the Cayenne S Hybrid is actuated by a triple cam on the intake camshaft. The following components are also integrated in the pump: Pressure control valve Fuel pressure sensor for low pressure Flow control valve Pressure damper, which reduces the pulsations in the supply. Pump drive shown above. Fuel/Ignition Diagnosis & Repair Page 5.17

64 Fuel Supply Systems Fuel Injectors Sports Cars (9x1) Sports Cars (991) The 3.4 liter and 3.8 liter engines use injectors with a different injection mass. The engine-specific assignment of the injectors is via the part number as well as a colored identification clip (Position 1) on the injector. 1 Fuel high-pressure pump (3 pistons) with quantity control valve (1.1) 2 High-pressure supply line 3 Connecting line (banks 1 and 2) 4 High-pressure rail 5 Fuel high-pressure sensor 6 Injectors (6 holes, with soft clip) New fuel injectors with 6 holes are used to ensure more efficient mixture formation, smoother running and maximum power. Shown above is the 6 hole injector. Sports Cars (981) New multi-port fuel injectors are installed for more efficient mixture formation, a smoother running engine and maximum power output. This illiustration shows a 6 hole injector on the right and a swirl injector on the left. The 2.7 liter and 3.4 liter engines use injectors with a different port pattern and injection mass. The engine specific assignment of the injectors is via the part number as well as a colored identification clip (Position 1) on the injector. Page 5.18 Fuel/Ignition Diagnosis & Repair

65 Fuel Supply Systems 3.4 l DFI = Pink identification clip (six-port injector) 2.7 l DFI = Orange identification clip (four-port injector) This injector delivers approx. 20% less mass over the same injection time. Injector Holder Clip Sports Cars (9x1) Using a softer clip to hold the injector dampens the noise made by the injector when closing. This is necessary because the modified thermodynamics resulting from the multi-port injectors means that knock detection reacts very sensitively in the rev range under 3,000 rpm. 1 Adaptation range 1 2 Adaptation range 2 3 Adaptation range 3 4 Adaptation range 4 5 Adaptation range 5 ccm Flow rate (in ccm/revolution) A Activation current for flow control valve (amperes) Fuel High Pressure Adaptation for Continental DFI The flow control valves in the 3- and 6-piston high-pressure pumps have flow tolerances between the individual valves due to their design. For this reason, the characteristic while driving is adapted to suit the relevant components by the high-pressure adaptation ranges 1 to 5. The graph shows the characteristic spread, which is balanced out by the high pressure adaptations 1 to 5. The respective adaptation range for operating states 1 to 5 is 0.75 to 1.25 (mean value: 1.00). Fuel High Pressure Adaptation Map hpa Fuel pressure mg/stk Injection volume rpm Engine speed Notes: Fuel/Ignition Diagnosis & Repair Page 5.19

66 Fuel Supply Systems Fuel Tank Ventilation System Fuel Tank Ventilation System With Active Carbon Filter Besides the HC emissions produced during combustion in the engine, other quantities of hydrocarbons are produced on the vehicle as a result of fuel evaporation in the fuel tank and in the fuel system. Active Carbon Filter The fuel vapors that occur are routed through a canister filled with active carbon and are deposited (adsorbed) there on the surfaces of the active carbon. The fuel in the fuel tank can be heated by: the ambient temperature or sunlight air flowing past the engine, which is heated up as a result the excess fuel that flows back from the fuel circuit and was heated up in the engine compartment (not with RF systems) the heat loss from a fuel pump installed in the fuel tank A - From the tank B - To the engine C - Purge air line D - Shut-off valve The carbon canister has four connections: 1 Fuel tank 2 Carbon canister 3 Tank vent valve TEV (activated by the DME control unit) 4 Rollover valve 5 Reservoir The fuel tank ventilation system with active carbon filter prevents the fuel that evaporates when the fuel in the fuel tank is heated from entering the environment. The evaporating fuel is adsorbed by the active carbon in the carbon canister (2) and supplied to the intake system via the tank vent valve (3) during engine operation to be burned. Connection A connects the carbon canister to the fuel tank. A rollover valve on the tank prevents the canister from overfilling with fuel if the vehicle is at an unacceptable extreme angle Connection B leads to the tank vent valve and from there to the intake side of the engine Connection C is the purge air connection through which the canister is connected to the outside air Connection D goes to the shut-off valve When the engine is running, some of the intake air is routed through the carbon canister as a function of the operating point and the active carbon is regenerated again. The air flow desorbs (releases) the fuel components from the active carbon and sends them to the engine for combustion. Page 5.20 Fuel/Ignition Diagnosis & Repair

67 Fuel Supply Systems Tank Vent Valve The tank vent valve is integrated in the engine compartment. It is activated so that sufficient flushing of the carbon canister takes place and deviations from λ = 1 are minimal. The tank vent valve is activated both by the variation of the pulse/duty factor and by the frequency. When the activation frequency is as high as possible, you get a good, timely uniform distribution to all cylinders. When the activation period is as long as possible (low frequency), you get good metering of small quantities. For these reasons, a long activation period (132 ms) is selected for pulse/duty factors of < 15 %, a medium activation period is selected for pulse/duty factors of < 30 % and a short activation period (high frequency) is selected for pulse/duty factors of 30 % - 70 %. The choice of installation position for the tank vent valve is influenced by the following factors: The spatial uniform distribution of the regeneration gas flow to the individual cylinders The objective here is to achieve the best possible uniform distribution of gases to the whole engine The purge quantity at full throttle. A sufficiently large purge quantity must be achieved at full throttle using a Venturi effect Filtering of the tank vent valve pulsations. The entire intake manifold must be used for maximum damping of pulsations A good installation position is directly behind the throttle valve. The regeneration flow mixes optimally with the intake air in the downdraft of the throttle valve and this ensures a very good uniform distribution. 1 Line connection 2 Check valve 3 Leaf spring 4 Sealing element 5 Magnetic armature 6 Sealing seat 7 Magnetic coil Load-dependent Fuel Tank Ventilation A mixture ratio of λ = 1 is also required during active fuel tank ventilation. The percentage of fuel in the regeneration gas flowing from the carbon canister into the intake manifold depends on the carbon canister load and must therefore be known and taken into consideration for the injection volume. The relative percentage of fuel in fuel tank ventilation system is calculated from the current pulse/duty factor of the tank vent valve, the load signal and oxygen sensor closed-loop control and is deducted for defining the current injection volumes. Notes: Fuel/Ignition Diagnosis & Repair Page 5.21

68 Fuel Supply Systems Diagram of Tank Leakage Test System with ORVR 1 - Fuel tank 2 - Rollover valve 3 - Fill level limit valve 4 - Spit-back valve 5 - Filler pipes 6 - ORVR valve 7 - Underpressure limit valve 8 - Pressure sensor 9 - Operative venting valve 10 - Filter casing 11 - Fresh air valve 12 - Shut-off valve 13 - Active carbon canister 14 - Air filter 15 - Tank venting valve 16 - Engine 911 Carrera 996 and Boxster 986 The above operating diagram shows the ORVR principle of the 911 Carrera 996 and Boxster 986. In the diagram above we can see the ORVR path indicated in red. The ORVR system is not electronic, it has two electromechanical solenoids, the ORVR valve at (6) and the fresh air valve at (11), they open when the reed switch at (9) is closed by a magnet on the back of the filler pipe flap. The ORVR is not monitored by the engine management system, it only operates during refueling and cannot affect the tank leak test. The spit back valve at (4), only allows liquid fuel to pass into the tank, it will not allow the vapors in the tank to pass back up the filler pipe. So as the tank fills, the vapors in the tank are forced to take the path indicated in green through the active carbon canister where the HCs are captured. When the fill limit valve at (3) closes the vapor path, the gas station filler nozzle will shut off. It is important that the tank not be topped off after the nozzle shuts off. We see that the ORVR overlays the tank ventilation system (vapor path shown in green) and the tank leak system so we have three vapor systems interconnected in this diagram. Looking at the diagram as one system can be confusing, however if we look at the diagram one system at a time, system operation becomes clear. On-Board Refueling Vaporation Recovering (ORVR) USA vehicles have a system in which fuel vapors that occur while refuelling the vehicle are routed into the active carbon filter. ORVR stands for: On-board Refueling Vaporation Recovering system, i.e. a fixed (on-board) system in the vehicle that recovers fuel vapors during refuelling. Notes: Page 5.22 Fuel/Ignition Diagnosis & Repair

69 Fuel Supply Systems Cayenne and Panamera (LDP) This illustration shows the system design for USA vehicles. Cayenne and Panamera Evaporative Emissions System 1 Filler opening 2 Degassing tank (ORVR, one-piece) 2.1 Operating vent lines for the tank 2.2 Refuelling vent line 3 Connection to the active carbon filter 4 Pressure retaining valve 5 Active carbon filter (ORVR with flange for leakage diagnosis pump) 6 Water separator with filter element and fresh-air intake 7 Leakage diagnosis pump 7.1 Vacuum line from intake manifold to leakage diagnosis pump 8 Cut-off valve 9 to the tank vent valve in the engine compartment 1 - Carbon Canister 2 - Vacuum Limiting Valve 4 - Over Pressure Relief Valve 3 - Percolation Tank 5 - Filler Neck (with metal flap) 6 - Fuel Tank 7 - Spring Loaded Flap 8 - Fill Limit Venting Valve 9 - Roll Over Valves 10 - Over Pressure Valve 11 - Refueling Vent Line 12 - Evaporative Valve 13 - Evaporative Vent Shutoff Valve 14 - LDP 15 - Vacuum Inlet 16 - One Way Check Valve 17 - Tank Vent Lines 18 - Fresh Air Vent With Filter The vapor collection system has five venting points on the tank; fuel vapors would collect in the high points of the tanks irregular shape if the extra vapor paths were not provided. In addition, it has a percolation chamber between the tank and the active carbon canister where heavy fuel vapors are allowed to condense back into liquid and return into the tank. The LDP system vents the tank to atmosphere across the active carbon canister. The fuel vapor-purging path is shown in green and has a vacuumlimiting valve (2) to reduce fuel evaporation. Fresh air enters via the air filter at (18) and moves through the active carbon canister at (1) where the HCs are picked up. The vapors then flow across the purge valve at (12) and into the intake manifold. The ORVR vapor path is shown in red. The ORVR system has no electrically controlled valves. Similar to the sports car system, it has a vapor control valve at the bottom of the filler pipe at (7). This allows liquid fuel in but no vapors out. The vapors are forced to exit at the fill limit valve at (8) and then through the active carbon canister (1) to atmosphere at the air filter at (18). Fuel/Ignition Diagnosis & Repair Page 5.23

70 Fuel Supply Systems The Cayenne and Panamera has three systems connected to the fuel tank: 1. Evaporative Emissions, 2. ORVR, and, 3. Tank Leak Check. The LDP is a diaphragm pump, above the diaphragm is a chamber that when the leak test begins is alternately connected to vacuum and atmosphere by an electric frequency valve operating at approximately 40% duty cycle. If we look at one system at a time operation is much easier to understand. Tank Leakage Monitor Diaphragm Lifting LDP (leak detection pump) 1 - Vacuum connection 2 - Electric frequency valve for the diaphragm pump 3 - Vacuum side of the diaphragm pump 4 - Pressure side of the diaphragm pump 5 - Connecting pipe to the carbon canister (pressure side) 6 - Connecting pipe to the water separator/filter element 7 - Electrical Reed Switch 8 - Mechanical EVAP shut-off valve (always closed when monitor is active) When the upper chamber is under vacuum, the diaphragm lifts and compresses the spring that normally holds it in the down position. When the upper chamber is vented to atmosphere, the diaphragm is moved by the spring to the down position. The bottom chamber is connected to atmosphere via the air filter over a one-way valve that only allows flow in (intake valve) and to the sealed tank via a one-way valve that only allows flow out (outlet valve). As the diaphragm moves up and down it pulls air in across the inlet valve and out across the outlet valve pumping air into the tank. As we see from the system diagram, the LDP is in series with the EVAP vent air filter and in parallel with the EVAP vent shut off valve, so when the EVAP vent shut-off valve closes, the only path into the tank is the LDP. The LDP is a vacuum operated pump and pumps air into the tank which is a sealed system, since during diagnosis the purge valve is closed. Diaphragm Falling As the tank pressurizes, the diaphragm has to act against the pressure built up in the tank, and as the pressure beneath the diaphragm becomes higher than the pressure above the diaphragm, the diaphragm stops falling completey down and begins to operate with a shorter stroke. When the pressure in the tank reaches a point where it overcomes the spring above the diaphragm, the diaphragm is locked in the fully raised position. Page 5.24 Fuel/Ignition Diagnosis & Repair

71 Fuel Supply Systems In the top of the LDP is a reed switch and a magnet. The magnet holds the reed switch in the closed position. As the diaphragm raises, a metal plate connected to the diaphragm slides between the reed switch and the magnet and the reed switch opens. The LDP frequency valve operates for a fixed period of time and then shuts off. If the reed switch has not opened, a major leak is detected, if the reed switch opens too soon, a small leak is detected, and if the switch remains closed for the required diagnostic period, the tank passes the leak test. In the bottom of the LDP there is a mechanical EVAP vent shut-off valve, it is opened when the diaphragm is in its full-relaxed position and duplicates the function of the electrical EVAP shut-off valve. The fuel vapor-venting path of the 9x7 Sports Cars shown in red is simplified compared with the earlier sports car system. Air enters through the air filter in the DM-TL, flows across the activated carbon canister picking up HCs, and then flows into the intake manifold via the venting valve. The ORVR vapor path shown in green is also simplified, there is a valve at the bottom of the fuel filler pipe to prevent vapors from venting up the filler pipe during fueling, and a fill limit valve as in the earlier ORVR. With DM-TL, ORVR and Evaporative emissions share vapor lines, this reduces the number of lines in the system. DM-TL Fuel Tank Pressure Test DM-TL Fuel Tank Leak Test Sports Cars (9x7) Tank Venting Canister Purge 1 - Fuel pump with pre-chamber 2 - Fuel filter 3 - Fuel-pressure regulator 4 - Fuel pressure line to the injection valves 5 - Purging line to the intake manifold 6 - Evaporative emissions purge valve 7 - Roll-over valve 8 - Four chamber carbon canister 9 - Tank leakage diagnostics module DM-TL 10 - Filter for DM-TL 11 - Vent to atmosphere 12 - ORVR vapor line 13 - Overpressure control valve (max. 130 mbar) 14 - Pressure control valve 15 - Excess-pressure control valve 16 - Fuel limit control valve 17 - Fuel filler pipe 18 - Anti-spitback valve When we look at the diagram of the DM-TL diagnosis module, we see that it consists of a pump, a two-position switching valve, and a.5mm (.02 in) orifice. It is connected on one side to the fuel tank across the active carbon canister, and on the other side to atmosphere across the air filter. When diagnosis is not active, the valve connects the atmospheric vent with air filter to the active carbon canister. Fuel/Ignition Diagnosis & Repair Page 5.25

72 Fuel Supply Systems Diagnosis Reference Measurement When diagnosis is initiated, the DM-TL valve is in a position that connects the pump to the reference orifice, and, the pump is switched on. The amount of current the pump consumes when pumping against the reference orifice is measured and stored by the diagnosis program. The purge valve is closed and the DM-TL valve is then moved to a position that closes off the path to atmosphere and opens a passage to the tank across the active carbon canister. Evaporative Emissions and Tank Leak Check General notes: The comprehensive component monitor checks all of the circuits and electric components in the evaporative emissions and tank leakage systems. It will store a fault if there is a malfunction detected in the components, or circuits, whenever the system is operating. If the active monitor detects a malfunction, the MIL will be illuminated when the conditions for confirming that fault are met. An appropriate fault will be stored in memory. This occurs only when the monitor is running. The diagnostic monitors run when the conditions for operation are met. This is not necessarily every time the vehicle is operated. Diagnosis Leak Test The pump begins to pressurize the tank and active carbon canister, and at this point, the amount of current that the pump consumes falls off. As the fuel tank and active carbon canister pressurize, the current rises. If the fuel tank active carbon canister and connecting pipes are leak tight, the current rises above the level previously recorded by the diagnosis program. The required conditions for diagnosis are different for the three systems, and can include engine temperature, load, RPM, time, and other variables. For example; the pressure sensor tank leak test and LDP tank test must be run when the engine is running, while the DM-TL leak test can be run without the engine running, or even with the key off. So when we repair a defect in the tank, or connected lines and components, it is important to perform a short test (except NVLD). If we do not this, the system may not run the diagnosis for a period of time. When it does, the MIL will turn back on if the vehicle is not repaired. If the current rises to the level previously recorded (when pumping against the reference orifice), then the leak is.5mm (.02 in.) in size. If the current is less than this level, the leak is larger than 0.5mm. The diagnosis is run for a specified time period and there is a coarse and fine test. Page 5.26 Fuel/Ignition Diagnosis & Repair

73 Fuel Supply Systems Tank Ventilation Sports Cars (9x1) Carbon Canister With Tank Leakage Diagnosis For the first time at Porsche, the 9x1 vehicles intended for the USA feature the NVLD (Natural Vacuum Leak Detection) system for tank leakage diagnosis. With this system, tank leakage diagnosis is performed as a passive longterm test when the vehicle is stationary for an extended period, which means that no short test is now required for this purpose. On vehicles with NVLD, the DME actual value A095 indicates whether the tank system was leak-free during the most recent long-term test in the stationary vehicle. Components and Function Evaluation Unit The installation position of the evaluation unit is directly above the fuel tank (Figure 5), underneath the battery tray (Figure 6). 1 Carbon canister for USA (installed in front of the battery) 2 NVLD evaluation unit with temperature sensor (installed under the battery holder) 3 NVLD module (pneumatic part) 4 Ventilation filter 5 Fuel tank 6 Battery tray The NVLD system consists of an NVLD evaluation unit (Figure 2) electronic part with temperature sensor) and an NVLD module (Figure 3 - pneumatic part). 1 DME control unit 2 NVLD evaluation unit with temperature sensor 3 NVLD module (pneumatic part) 4 Carbon canister 5 Tank vent line 6 Tank vent valve 7 Throttle valve (electronic throttle) The following components (electronic part, Figure 2) are also installed here: Temperature sensor Evaluation unit (self-diagnosing) with: Timer Memory Communication interface with the DME control unit Fuel/Ignition Diagnosis & Repair Page 5.27

74 Fuel Supply Systems The NVLD evaluation unit is connected to the switch in the NVLD module via a two-wire cable. It is supplied externally with 12 volts and ground (terminal ). The third external connection on the NVLD evaluation unit is the communication line which is connected to the DME control unit. No Leak Example 1 Operating Principle The leak test is performed on the basis of Amontons Law (the Gas Law), which states that pressure is proportional to temperature in a closed system. This means that a change in pressure can be deduced from a change in temperature. Ø0.5 mm Leak Example 2 The system is sealed gas-tight (unlike previous methods) after the engine is switched off. This means that a change in temperature in the system will have a direct effect on the pressure. The system is leak-free if a drop in temperature (long-term cooling) causes the pressure in the fuel tank to fall below -2.5 mbar relative pressure (vacuum relative to ambient pressure). The fuel tank ventilation system can be regarded as being leak-free if all leaks together correspond to a leak with a diameter of max. 0.4 mm (=0.016 inches). The system is also leak-free if the pressure in the fuel tank after the engine is switched off is below -2.5 mbar relative pressure and this vacuum is maintained for at least 20 minutes. Example 1 shows the long-term test for a leak-free system. 1 Pressure curve in the tank system (red) 2 Temperature (blue) 3 Time Example 2 shows the long-term test for a system with a leak. Notes: Page 5.28 Fuel/Ignition Diagnosis & Repair

75 Fuel Supply Systems NVLD Module (pneumatic part), Operating Principle Under Vacuum NVLD: Mechanical Function Vacuum at -6.0 mbar This component is located directly on the carbon canister. The illustration below shows a leak-free system with the switching point of the vacuum switch at -2.5 mbar. Illustration 6 shows a leak-free system at maximum vacuum of -6.0 mbar. The conical seal (5) limits the vacuum when the diaphragm is raised. Opens at -6.0 mbar, closes at -3.0 mbar. NVLD Module (pneumatic part), Operating Principle Under Pressure NVLD: Mechanical Function At Reset 1 Vacuum (light blue) 2 Atmosphere (blue) 3 Switch (switching point -2.5 mbar) 4 Diaphragm 5 Conical seal If long-term cooling causes a vacuum (1) of -2.5 mbar in the fuel tank after the vehicle is switched off, the diaphragm (4) moves upwards and closes the switch (3). The electric vacuum switch (3) is actuated by vacuum when the diaphragm is raised. It closes and opens at -2.5 mbar relative vacuum. Illustration 7 shows the NVLD module at ambient pressure. The ventilated NVLD module and diaphragm (4) are in neutral position. Fuel/Ignition Diagnosis & Repair Page 5.29

76 Fuel Supply Systems NVLD: Mechanical Function Pressure at mbar Leak Test The NVLD tank leakage diagnostic system is passive. It works by measuring the pressure difference between the warm and cold fuel tank. In order to reliably determine the absence of leaks in the system, the fuel tank must be left to cool down for an extended period of time (e.g. overnight). This means that it is not possible to check whether the tank system is leak-free by means of a quick test using on-board diagnosis after a repair. Illustration 8 shows the NVLD module at 1 mbar overpressure. The diaphragm moves downward in the event of overpressure and opens the conical seal (5). Opening starts at +1.0 mbar. Consequently, a smoke test is provided for performing a quick leak test of the tank system using NVLD in the workshop. The smoke test is described in the PIWIS information system. NVLD: Mechanical Function Pressure at + 5 mbar Illustration 9 shows the NVLD module at +5 mbar (fully open at maximum overpressure). In other words, the pressure in the fuel tank always moves between mbar in the stable condition. Note! On vehicles with NVLD, the DME actual value A095 indicates whether the tank system was leak-free during the most recent long-term test in the stationary vehicle. Page 5.30 Fuel/Ignition Diagnosis & Repair

77 Exhaust Systems Subject Page General Information Boxster (987) Exhaust System Carrera/S (991) Exhaust Systems Cayenne Turbo Exhaust System Panamera S Exhaust System Sports Exhaust Systems Emission Control Catalytic Converters Secondary Air Injection Oxygen Sensors Fuel/Ignition Diagnosis & Repair Page 6.1

78 Exhaust Systems Exhaust System/Emission Control The exhaust system includes the components through which the combustion gases escape from the combustion chambers into the open as well as the components involved in emission control. These include the exhaust manifolds, the primary and main catalytic converters together with the oxygen sensors, the front and main silencers and the tailpipes. General Information The combustion of the air/fuel mixture in the engine is never complete. Fuel that does not burn is delivered into the exhaust system during the exhaust stroke and does not therefore contribute to torque build-up. This always results in HC and CO raw emissions. The exhaust system components, such as the exhaust manifold, the primary and main catalytic converters with the oxygen sensors and the front and main mufflers with the tailpipes are precisely matched components of a control loop, which must ensure optimum exhaust gas post treatment not only when the engine is at operating temperature, but also when starting the engine and in the warm-up phase. The arrangement and even the number of the components in the exhaust system differ depending on the model. Boxster (987) From the exhaust manifolds (1), the exhaust gases flow to one oxygen sensor (2) per cylinder bank. They then flow to one ceramic primary catalytic converter (3) per cylinder bank. Downstream of the catalytic converters, the exhaust gases flow via downstream oxygen sensors (4) to the ceramic main catalytic converter (6) and on to the rear silencer (7). From the rear muffler they flow via the connecting tube (8) to the tailpipe (9). 1 - Exhaust manifold 2 - LSU broadband oxygen sensor 3 - Primary catalytic converter (ceramic) 4 - LSF oxygen sensor 5 - Front pipe insulation with ceramic mat lining 6 - Main catalytic converter (ceramic) 7 - Rear muffler 8 - Connecting tube 9 - Individual tailpipe cover The exhaust gases from the left-hand and right-hand banks are mixed via the connecting tube (8). Notes: Page 6.2 Fuel/Ignition Diagnosis & Repair

79 Exhaust Systems 911 Carrera (991) Exhaust System for the 3.4-liter Engine 911 Carrera S (991) Exhaust System for the 3.8-liter Engine The 3.4-liter engine features a twin-branch exhaust system with catalytic converters arranged close to the engine (1) on the flow-optimized exhaust manifold, a common front muffler (2), two main mufflers (3) and individual tailpipe covers (4) as standard. Layout of the 911 Carrera S flap exhaust system (standard on the S model) The 3.8-liter Carrera S engine features a four-branch exhaust system with catalytic converters arranged close to the engine (1) on the flowoptimized exhaust manifold, a common front mufflers (2), two flap-controlled bypass pipes (3), two main mufflers (4) and two twin tailpipe covers (5). The main mufflers (4) have an intake pipe with a diameter of 55 mm and an exhaust pipe with a diameter of 52 mm. The main mufflers (3) have an intake pipe and exhaust pipe with a diameter of 55 mm. The exhaust system has been derestricted by optimizing flow characteristics in order to reduce exhaust backpressure. The map-controlled, electropneumatic flap control of the 911 Carrera S exhaust system increases the engine power by further reducing exhaust backpressure at increased rpm and engine load. Twin-branch exhaust system 1 Catalytic converters arranged close to the engine on the exhaust manifold 2 One common front muffler 3 One main muffler per cylinder bank 4 Individual tailpipe covers Fuel/Ignition Diagnosis & Repair Page 6.3

80 Exhaust Systems Sports Exhaust System 911 Carrera/S (991) (available as an option for the 3.4-liter and 3.8-liter engines) 1 Catalytic converters arranged close to the engine on the exhaust manifold 2 Front muffler 3 With two exhaust flaps on the front muffler 4 One main muffler per cylinder bank 5 Twin tailpipe covers Exhaust Flap Switching (911Carrera S) The Carrera S exhaust system does not feature a switch for activating and deactivating the exhaust flaps. The exhaust flaps are activated using a map in the DME control unit as a function of engine speed and load: Engine speed: >3,300 rpm Load: Slight, partial-load acceleration (corresponds to an air mass of 400 mg/stk) In this case the DME control unit sends a CAN signal via the gateway to the rear-end electronics, which activate the electropneumatic switching valve. A completely redesigned sports exhaust system is available for the 911 Carrera (991) models. The main innovation to the sports exhaust system is an extended functionality. For the first time, activating the sports exhaust system not only derestricts the exhaust gas routing but also enables the two exhaust tracts to be connected. This pairs an unmistakable flat-six engine sound with optimum performance. This results in more emotive acoustics. Sporty sound and improved torque curve Two twin tailpipes with a unique nozzle design An acoustically optimized mode can be activated and deactivated by pressing a button When the sports exhaust system is activated, the indicator light in the button lights up Notes: For visual differentiation, the sports exhaust system has two twin tailpipes with a unique nozzle design and nanocoating. Page 6.4 Fuel/Ignition Diagnosis & Repair

81 Exhaust Systems Exhaust Flap Switching (sports exhaust system) On the optional sports exhaust system, switching of the exhaust flaps to an acoustically optimized mode can only be activated or deactivated following a request using one of the following buttons: Layout of the Sports Exhaust System (available as an option for the 3.4-liter and 3.8-liter engines) Sport button Sport Plus button Sports exhaust system button (the sports exhaust system can also be deactivated using this button). Four-branch sports exhaust system with catalytic converters arranged close to the engine on the flowoptimized exhaust manifold, a common front muffler (1) with central map-controlled, electropneumatically switchable exhaust flaps of the bypass pipes (3), two main mufflers (4) and two twin tailpipe covers (5) with unique nozzle design. The main mufflers (4) have an intake pipe with a diameter of 55 mm and, in some countries, an exhaust pipe with a diameter of 52 mm or 50 mm. On the sports exhaust system, activating the exhaust flaps also reduces the exhaust back pressure (for a sporty sound and improved torque curve) as well as establishing a connection between banks 1 and 2. The connection results in resonance induction between the left and right cylinder banks. The exhaust flaps are activated in accordance with the request using the map in the DME control unit, as on the Carrera S. In this case the DME control unit sends a CAN signal to the gateway; it receives the corresponding button request via CAN from the operating and air conditioning unit. Only then does the gateway send a CAN signal to the rear-end electronics, which activate the electropneumatic switching valve. 1 Front muffler with 2 Connection as well as 3 Two central exhaust flaps with modified positioning 4 One 52 mm main muffler per cylinder bank (50 mm in some cases) 5 Two twin tailpipes with a unique nozzle design Fuel/Ignition Diagnosis & Repair Page 6.5

82 Exhaust Systems Emission Control, Catalytic Converter, Oxygen Sensors 911 Carrera/S (991) The oxygen sensor LSF downstream of the catalytic converter (3) is installed seven tenths of the way along the length of the main catalytic converter; this corresponds to 84 mm from the intake surface. The funnel (4) upstream and downstream of the catalytic converter is air-gap insulated to reduce the emission levels. There is one three-way main catalytic converter with ceramic monolith (1) per cylinder bank installed at the end of the flow-optimized exhaust manifold. The catalytic converter diameter is 125 mm, the length 120 mm, it has 400 cells and a wall thickness of 4.5 mm. The vehicles comply with the worldwide exhaust emission standards: EURO 4 (EOBD) EURO 5 (EOBD) USA LEV II (OBD II) Bank-specific oxygen sensor closed-loop control with: 1 Ceramic main catalytic converter (three-way), left + right 2 Broadband oxygen sensors (LSU) upstream of catalytic converters 3 Oxygen sensors (LSF) downstream of catalytic converters 4 Air-gap insulated funnel upstream and downstream of catalytic converters Notes: Page 6.6 Fuel/Ignition Diagnosis & Repair

83 Exhaust Systems Cayenne Turbo 1 - Primary catalytic converter 2 - Decoupling element 3 - Main catalytic converter 4 - Rear muffler 5 - Twin-tailpipe The exhaust system of the Cayenne Turbo is adapted to the higher requirements as well as different exhaust gas speeds and exhaust gas pulsations compared with the Cayenne S by way of tailpipes with a larger cross-section. Note! The exhaust system of the Cayenne S has a connection between the exhaust tracts of banks 1 and 2 in the center of the parallel tailpipes. This connection results in improved torque at a low engine speed. Panamera S A special exhaust system made of long-life stainless steels is used for the Panamera S and 4S. The exhaust gases enter the front muffler (1) downstream of the primary and main catalytic converters (cascade catalytic converter 3/4). The front muffler contains an integrated connection between the left and right exhaust tracts; the rear muffler (2) on the right and left have twintailpipe covers. Fuel/Ignition Diagnosis & Repair Page 6.7

84 Exhaust Systems Sports Exhaust Systems Sports exhaust systems are offered for most Porsche models. When the Sport button is pressed, the tone of the sports exhaust system is controlled via a map by the DME control unit taking into account the load, speed, engine speed and gear to produce the rich and full typical Porsche sound. Cayenne S (optional only for the Tiptronic S) The sports exhaust system is activated using the standard Sport button. Like the standard exhaust system up to the muffler, the sports exhaust system has two primary catalytic converters and two main catalytic converters, the two exhaust tracts of which are connected via a crosscoupling point downstream of the main catalytic converters. Two gas-conducting tailpipes run to the left and right into the distinctive chrome-plated, stainless-steel twin-tailpipe covers. 1 - Twin-branch exhaust system 2 - Sports exhaust system muffler 3 - Vacuum line for activation 4 - Diaphragm cell for switching 5 - Two tailpipes at the left and right with twin-tailpipe covers Note! Suitability for off-road driving (fording depth) is reduced when the sports exhaust system is installed. Panamera S Like the standard exhaust system, the sports exhaust system on the Panamera S up to the rear muffler consists of two primary catalytic converters and two main catalytic converters as well as a center muffler. There are two exhaust flaps (2) between the rear mufflers (1) and the tailpipe covers that are opened by the electro-pneumatic switching valve (3) between the rear mufflers in order to achieve improved throughput. A connecting web gives them a unique look reserved exclusively for the Cayenne S with sports exhaust system. The tailpipes are integrated into the rear lower section of the Cayenne Turbo, which is part of the optional sports exhaust system package. Page 6.8 Fuel/Ignition Diagnosis & Repair

85 Exhaust Systems Emission Control The exhaust gas flows through the catalytic converters in the exhaust tract before it is released into the open air. When the operating temperature of the catalytic converter is reached, suitable coatings in the catalytic converter make sure that the pollutants in the exhaust gas undergo a chemical reaction and are converted into non-toxic substances. The oxygen sensors measure the residual oxygen content in the exhaust gas. This enables the airfuel mixture to be controlled in such a way that the catalytic converter is operated at optimum efficiency. Thermal Post Treatment When the engine is cold, uncombusted fuel coming from the combustion chamber condenses on the cold cylinder walls. To keep the engine running smoothly and steadily despite this, the air/fuel mixture must therefore be enriched during the warm-up phase. To make matters worse, the catalytic converter must have reached a temperature of around 482 F. (250 C.) before it can convert the pollutants. It is important therefore to minimize the raw emissions during the warm-up phase before the catalytic converter starts. This is done using the following measures, for example: Catalytic Converters In the three-way closed-loop catalytic converters, the main pollutant components in the exhaust gas CO, HC and NOX are converted chemically through oxidation and reduction and are thereby reduced considerably. Catalytic converters consist of a substrate with an active coating and shake-resistant, heat-insulated lagging in one housing. Ceramic or metallic monoliths are used as the substrate. The active catalytic converter layer consists of small amounts of precious metal (Pt -- platinum, Rh -- rhodium, Pd -- palladium) and is sensitive to lead. The catalytic converter only begins any significant conversion of pollutants at a temperature of approx. 482 F. (250 C.) or higher. Operating conditions for high conversion rates and a long service life are ideal at approx. 752 to 1472 F. (400 to 800 C.). The maximum permitted temperatures are just over 1832 F. (1,000 C.). The exhaust gas temperature is therefore simulated in the control unit using a model. If the temperature rises above a certain threshold, the exhaust gas temperature can be reduced by making the mixture richer as heat is extracted from the exhaust gas in order to evaporate the fuel. The charge and torque limits are modified on ME systems. High exhaust emissions temperatures using a late timing angle and a large mass gas flow Catalytic converters located close to the engine Dual injection with direct fuel injection systems Secondary-air injection (if equipped) Notes: Fuel/Ignition Diagnosis & Repair Page 6.9

86 Exhaust Systems Oxygen sensor closed-loop control adjusts the mixture in the engine s combustion chamber so that the catalytic converter is working at its optimum and therefore the emissions limits are adhered to. The catalytic converter therefore has the task of converting the three exhaust gas components carbon monoxide CO, hydrocarbon HC and nitrogen oxide NO x into CO 2 (carbon dioxide), H2O (water vapor) and N2 (nitrogen). The conversion rates differ significantly depending on the air ratio in the catalytic converter. In addition, the catalytic converter s conversion rate drops as the aging process increases if significant oxygen fluctuations occur in the engine s operation. The bottom illustration shows that when there is a lack of oxygen (λ < 1), nitrogen oxide NO x can be converted very well, but hydrocarbon HC and carbon monoxide CO are not converted well. If there is surplus oxygen (λ > 1), the situation is reversed. The optimum operating point of the catalytic converter is therefore in the air ratio range Picture above: Exhaust emission values upstream of the catalytic converter. Picture below: Exhaust emission values downstream of the catalytic converter. Different catalytic converters are installed depending on the vehicle type, engine and model year. The catalytic converters used in earlier vehicles were mainly metal; ceramic catalytic converters are now frequently used. A distinction can be made between the following variants: Main catalytic converters only Primary catalytic converter and main catalytic converter separate Cascade catalytic converter (primary and main catalytic converter in one housing) Primary and Main Catalytic Converters - DFI/MPI Opposed Engines The catalytic converters used in DFI flat engines are integrated directly behind the right and left manifold pipes. Previously, they were located transversely behind the engine. This location close to the engine and the integration into the manifolds (without an additional flange connection) not only reduces weight, but it also significantly improves the efficiency of the catalytic converters particularly after cold starting. In combination with the special DFI catalytic-converter heating phase, it is also so efficient that the secondary-air injection that was previously additionally used can now be omitted for the new models. Therefore, it was possible to relocate the catalytic converters from the crash sensitive rear area to the side near the engine. The primary catalytic converter and main catalytic converter are in the same housing. The substrate of the primary catalytic converters and main catalytic converters consists of ceramic material. The first catalytic converter (primary catalytic converter) near the engine, with its low volume, reaches its operating temperature shortly after the engine starts. This means that it not only reduces the pollutants when the engine has reached its operating temperature, but also during the warm-up phase. Page 6.10 Fuel/Ignition Diagnosis & Repair

87 Exhaust Systems The following main catalytic converter is used to stay below the applicable emissions limits even with high mileage. It was therefore possible to make the coated inner walls thinner than in ceramic catalytic converters, for example, thereby achieving a larger total surface area on the catalysing ducts. This ensures a faster warm-up, high durability and more efficient conversion of pollutants. Even in the warm-up phase, the operating temperature for emission control is reached more quickly. Furthermore, a metal catalytic converter is less sensitive to heat, impacts, and ages more slowly. Higher engine power is also achieved due to the lower exhaust backpressure. 1 - Exhaust manifold 2 - LSU oxygen sensor 3 - Primary catalytic converter 4 - Installation position of LSF oxygen sensor (covered by the main catalytic converter) 5 - Main catalytic converter Primary and Main Catalytic Converters - V8 DFI Engines The V8 DFI engines have twin-branch exhaust systems. The primary and main catalytic converters used in the Cayenne V8 are made of metal. Metal catalytic converter substrates only have 1/3 of the wall strength of ceramic substrates. As a result, they are more compact and have a larger active surface for converting pollutants. 1 - LSU oxygen sensor (upstream of primary catalytic converter) 2 - LSF oxygen sensor (downstream of primary catalytic converter) 3 - Primary catalytic converter (bank 1) 4 - Main catalytic converter (bank 1) 5 - Exhaust manifold 6 - Turbocharger 7 - Boost-pressure control valve 8 - Decoupling element Notes: Fuel/Ignition Diagnosis & Repair Page 6.11

88 Exhaust Systems Given the high temperatures that a catalytic converter needs to start the emission control process fully effectively as quickly as possible after a cold start, the exhaust gases are supplied via a double-wall, air gapinsulated exhaust manifold with the shortest possible pipe lengths in order to heat the primary catalytic converters quickly. Up to the main catalytic converter, which is designed as an underfloor catalytic converter, all exhaust pipes are airgap insulated to prevent heat loss (see illustration for exhaust manifold in the Cayenne S MY 2003). Secondaryair injection is also used to improve heating of the primary catalytic converters after cold-starting the engine. Operating Principle A check valve allows additional air to be injected into the exhaust system upstream of the catalytic converter for a defined period by means of the secondary-air pump. The rich engine operation in this operating state produces a higher level of carbon monoxide (CO) and hydrocarbon (HC) in the exhaust gas, which is combusted using the secondary air injected right behind the exhaust valves. The heat that is released during post-combustion means that the optimum operating temperature of the catalytic converter for optimum exhaust post-treatment is reached more quickly. Air injection systems were and are installed in accordance with country-specific emissions standards. Air Injection System in the Cayenne S and Cayenne Turbo The 4.5-liter Cayenne V8 engines from MY 2003 thru 2010 had two separate air injection systems for the cylinder banks on the left and right. The secondary-air valve (3) was opened by the air pressure of the activated secondary-air blower. On the Cayenne Turbo, the secondary-air valve (3) is different in that it also has an integrated check valve. 1 - Exhaust manifold (Cayenne S MY 2003) 2 - Air gap for insulation 3 - Broadband oxygen sensor (LSU) 4 - Flange to primary catalytic converter Secondary-Air Injection Compliance with emissions limits requires that the catalytic converter(s) is(are) specifically heated in order to reach the conversion temperature quickly. In practical terms, the use of the chemical energy in the exhaust gas requires the introduction of secondary air into the exhaust tract upstream of the catalytic converter, whereby exactly what is required from the air injection system (blower power, introduction point of the air flow, etc.) depends on the catalytic converter heating strategy used. 1 - Secondary-air blower (left and right) 2 - Connecting hose 3 - Secondary-air valve 4 - Flange with air duct 5 - Air guide behind the exhaust valves Page 6.12 Fuel/Ignition Diagnosis & Repair

89 Exhaust Systems Oxygen Sensors General Information The oxygen sensor measures the difference in oxygen concentration between the ambient air and exhaust gas flow. The measuring signal output by the sensor is therefore a direct measure of the air ratio in the exhaust gas. Important! When working on oxygen sensors, please note the working regulations and warnings in the PIWIS information system such as: Do not use contact spray or grease on the oxygen sensor s plug connections (otherwise there is a risk that the reference air duct will be polluted, which leads to aging of the oxygen sensor) Cleanliness must be ensured when working on oxygen sensors Oxygen sensors must be protected against mechanical shocks The cables must not be twisted when the sensors are screwed in Oxygen Sensor Upstream of Catalytic Converter The signal from the oxygen sensor upstream of the catalytic converter is elementary for oxygen sensor closed-loop control. The oxygen sensor closed-loop control controls the fuel mass to be injected via the injection time of the fuel injectors to produce the right airfuel ratio. The cylinder charge and the timing angle are not influenced. Oxygen Sensor Downstream of Catalytic Converter The catalytic converter efficiency must be continuously monitored as per the OBD II regulations. A second oxygen sensor must be installed downstream of the catalytic converter for this. Comparing the sensor signals upstream and downstream of the catalytic converter permits statements about the efficiency of the catalytic converter. Notes: Fuel/Ignition Diagnosis & Repair Page 6.13

90 Exhaust Systems The continuous development process in the area of sensors is reflected in the different sensor designs: LSH heated oxygen sensor The LSH oxygen sensors are installed upstream and downstream of the catalytic converter in older systems. This jump-type sensor generates a voltage signal between 0 and 0.9 volts as a function of the oxygen content in the exhaust gas. LSF planar oxygen sensor On some models, the LSF oxygen sensor was installed upstream and downstream of the catalytic converter (now mainly downstream of the catalytic converter). This jump-type sensor also generates a voltage signal between 0 and 0.9 volts as a function of the oxygen content in the exhaust gas. LSU planar broadband oxygen sensor The LSU broadband oxygen sensor is a further development of the LSF oxygen sensor and is only installed upstream of the catalytic converter. It has an oxygen pump cell that the LSF does not and needs a special control circuit in the DME control unit. In contrast to the LSH/LSF jump-type oxygen sensors that merely indicate whether the engine mixture is lean or rich, the continuously measuring broadband oxygen sensor records the precise deviation from lambda Using electric heaters in the oxygen sensor means that there is no longer a dependence on these high exhaustgas temperatures. This means that an analysis of the air ratio in the exhaust gas can be performed above exhaustgas temperatures of just 302 F. (150 C.). Only heated oxygen sensors are still used on the current systems. The heating current is activated by the DME control unit. All oxygen sensors are based on the same measuring principle, only the technical implementation differs. Two-point Oxygen Sensor (LSH) based on the Nernst Principle LSH stands for Lambda Sensor with Heating (i.e. heated oxygen sensor). This additional information enables the mixture to be adjusted under all load conditions to ensure that the catalytic converter is operating effectively. This sensor was used for the first time on the 911 Turbo (996). It is now installed upstream of the catalytic converter on almost all models. The sensors are ready for operation at temperatures above approx. 662 F. (350 C.). The exhaust-gas temperature must therefore be over 662 F. (350 C.) for unheated sensors. Page Exhaust system 2 - Inner electrode 3 - Sensor ceramic material 4 - Outer electrode 5 - Exhaust gas flow 6 - Ambient air 7 - Sensor voltage (U) Fuel/Ignition Diagnosis & Repair

91 Exhaust Systems Due to the catalytic coating, mixture that is not completely burnt is always converted on the surface of the sensor. If there is still a lot of residual oxygen on the outer surface of the sensor (exhaust side), the air ratio must be in the lean range (λ residual oxygen on the outer surface of the sensor, there must have been rich mixture (λ < 1) in the exhaust gas. Characteristic The conventional two-point oxygen sensor LSH (heated oxygen sensor), also called finger sensor, has a transient response characteristic of 0 to 900 mv at lambda = 1. This sensor was last used on MY 2002 Boxster vehicles. The amount of oxygen on the outer sensor is therefore a measure of the air ratio in the exhaust gas. In practice, the voltage between the outside (exhaust gas) and inside (ambient air) of the sensor electronics is measured in order to determine the oxygen content. In a sensor that is ready for operation (electrically conductive), the electric voltage is produced by the difference in the concentration of oxygen between both sides of the sensor as oxygen ions are constantly formed on the catalytic coating. In this case, the output voltage for a rich mixture reaches about mv and about mv for a lean mixture. Notes: Fuel/Ignition Diagnosis & Repair Page 6.15

92 Exhaust Systems Oxygen Sensor LSF The LSF oxygen sensor (flat oxygen sensor) is a further development of the LSH oxygen sensor and also has a transient response characteristic of 0 to 900 mv at lambda = 1. In contrast to the LSH sensor, ceramic foils form the solid electrolyte in the LSF oxygen sensor. The sensor element of this planar oxygen sensor consists of ceramic foils and has the form of a long plate with a rectangular cross-section. The respective functional layers (electrodes, protective layers, etc.) are produced by means of a screen printing process. The manner in which the different printed foils are laminated one onto the other means that it is also possible to integrate a heating element in the sensor element. Broadband Oxygen Sensor LSU LSU stands for Lambda Sensor Universal. The LSU broadband oxygen sensor is a further development of the LSF oxygen sensor and is now installed upstream of the catalytic converter on most current vehicles. It has an oxygen pump cell and needs a special control circuit in the DME control unit. Illustration shows a cutaway view of the LSF oxygen sensor Special characteristics of the LSF oxygen sensor: -- Fast operational readiness -- Low heating power requirement -- Stable control characteristics -- Small, lightweight design In contrast to the LSF step oxygen sensor, which merely indicates whether the engine mixture is lean or rich, the continuously measuring broadband oxygen sensor measures precisely how lean or rich the mixture is. This additional information enables the mixture to be adjusted so as to ensure that the catalytic converter operates effectively. This is also possible when highly dynamic load changes apply. Vehicles fitted with this broadband oxygen sensor run with oxygen sensor closed-loop control shortly after cold starting, from idling up to full throttle. The LSF oxygen sensors are installed downstream of the primary catalytic converters to check the operation of the catalytic converters. 1 - Exhaust gas 2 - Reference air duct 3 - Heater element Us - Oxygen sensor voltage The above illustration shows a sectional view through the planar layer design of the LSF oxygen sensor. Page 6.16 Fuel/Ignition Diagnosis & Repair

93 Exhaust Systems Advantages of the LSU broadband oxygen sensor: -- Exact measurements from lambda > 0.7 (rich mixture) to lambda < 4 (pure air) are possible -- The LSU sensor supplies a continuous signal, which is evaluated in the DME control unit -- Controlled operation with oxygen sensor closed-loop control is possible in all conditions -- The broadband oxygen sensor is ready for use very quickly -- The oxygen sensor closed-loop control circuit responds faster to a change in the mixture -- Improved regulating action with increased dynamics Design of the LSU Broadband Oxygen Sensor The LSU consists of different planar functional layers. The actual sensor element of the broadband oxygen sensor consists of a combination of a Nernst concentration cell (1) and a pump cell (2) transporting oxygen ions. The broadband oxygen sensor requires a special operating electronics system (6) in the form of an evaluation circuit in the DME control unit. The evaluation circuit contains the internal control electronics for the pump cell and the sensor cell for generating the sensor signal. The control current of the electronic pump cell always generates lambda 1 in the measuring cell (3). This is monitored continuously via the voltage of the sensor cell (450 mv). The evaluation circuit calculates the precise lambda value of the exhaust gas on the basis of the deviation of the pump cell current (0 ma ± 1 ma). LSU temperature control is also integrated in the evaluation circuit. 1 ma). A - Exhaust Gas B - Heater Current C - Pump Current D - Reference Voltage 1 - Nernst Cell 2 - Pump Cell 3 - Diffusion Gap 4 - Reference Air 5 - Nernst Cell Heater 6 - Op Amp 7 - Measuring Resistor Operation The heart of the wide band sensor is a Nernst concentration cell this is the engineering term for a lambda oxygen sensor. So in the middle of the wide band sensor is a narrow band sensor, this sensor cell lies between the reference air channel at #4 and the exhaust gas flow coming in at A into measurement cell #3. The output from the sensor cell is connected to the negative terminal of an operational amplifier in the control unit. The other measurement terminal of the operational amplifier is connected to a fixed reference voltage at D. The Op amp compares the two voltages and based on the polarity and amplitude difference between the two voltages, the Op amp generates a current at its output. Fuel/Ignition Diagnosis & Repair Page 6.17

94 Exhaust Systems This current flows into or out of a second nernst cell #2 (it turns out that when we put an oxygen differential across a nernst cell it generates a voltage, and when we put a voltage across a nernst cell it moves oxygen), when the current flows in, it moves oxygen into the measurement cell, and when it flows out it pumps oxygen out. By pumping oxygen out of and into the measurement cell the Op amp keeps the difference between the reference voltage and the Nernst cell voltage stable. This means that the Nernst cell voltage is kept at 450 mv by the current flowing from the Op amp. It turns out that the voltage drop across the measuring resistor at #7 is directly proportional to mixture in the wide band. Wide band sensors are planar sensors. They are not thimble shaped like a conventional oxygen sensor, instead they are a bar of ceramic material like a stick of gum but much smaller and narrower and about the same thickness. Newer narrow band sensors and all Porsche wide band sensors are planar in design. The wide band sensors have a small hole in their upper surface that allows the exhaust gas flow to act on the measurement cell. In the connector of the wide band sensor there is a special laser trimmed resistor that is adjusted during production to calibrate the sensor. Wide band sensors have a sensor heater that controls the sensors temperature. This heater is fed a modulated square wave to control the sensor temperature. It is important that the wide band sensor be quickly heated up so it can begin to control mixture as quickly as possible and kept at operating temperature to ensure accurate operation. In the sensor wiring diagram we can see the color codes of the wires and the connection points to connect an oscilloscope to measure the voltage drop across the measuring resistor, the nernst cell voltage and the heater square wave. The oxygen sensor monitor for wide band sensors operates much like the sensor monitor for narrow band Lambda sensors. The sensor design is different, but the output wave form is similar. Wide Band Oxygen Sensor Wiring Diagram Page 6.18 Fuel/Ignition Diagnosis & Repair

95 Mixture Formation Subject Page General Information Basic Information Simple System Model Fuel Trim & Adaptive Mixture Control Systems Digital Motor Electronic (DME) Injection Method Gasoline Engines Piston Recesses DFI Engines Engine Operating States Injection Strategies DFI Engines Lambda Coordination Mixture Adaptation Fuel/Ignition Diagnosis & Repair Page 7.1

96 Mixture Formation General Information Basic Information When discussing mixture ratio in Porsche fuel systems we use the term Lambda (Short for Lambda1) to indicate a mixture at a ratio of 14.7 to 1 fuel to air by weight. It is also the term we use for oxygen sensors Lambda sensor, since Lambda sensors measure mixture. Below is the Power vs. Fuel economy graph, it illustrates the benefits of an air to fuel ratio at Lambda. Gasoline engines need a specific ideal air-fuel ratio at which optimum combustion of the fuel takes place. The DME control unit calculates the quantity of fuel to be injected relative to the air mass currently being taken in and engine RPM along with real time values i.e. engine temperatures by means of mixture formation. The ideal airfuel mixture is a mass ratio of 14.7 to 1. In other words, 14.7 kg of air mass is needed to burn 1 kg of fuel mass. This is also referred to as the stoichiometric ratio. The air ratio of lambda (1) is used to identify by how much the airfuel mixture actually present differs from the theoretically required mass ratio. Lambda (λ) =1, corresponds to a mass ratio of 14.7 to 1. Lambda (λ) <1, there is insufficient air, which means a rich mixture. Lambda (λ) >1, there is excess air, which means a lean mixture. When we analyze the Power vs. Fuel economy graph you can see the advantage of a air fuel ratio of Lambda 1: Notice that the curves have a steep section and a flat section. Move mixture to the max power point and you gain only a small increase in power and you have a large increase in fuel consumption. Move to the point of lowest fuel consumption and you gain only a small amount of fuel economy and lose a large amount of power. It becomes obvious that Lambda 1 (14.7 to 1 air fuel ratio) is the right mixture for best power with optimum fuel economy. We only need to move away from this mixture ratio when the engine is first started and when it is at full throttle. We will talk about why later. Page 7.2 Fuel/Ignition Diagnosis & Repair

97 Mixture Formation Simple System Model Let s talk about how the goal of the fuel system is achieved. The fuel control system is complex on late model Porsche vehicles, however we can gain a solid understanding of how this complex system works by reducing the system to its least complex form. We call this least complex form the simple system model. It consists of the following: A fuel pump to supply fuel to the engine. Electromechanical fuel injection valves to deliver the fuel. An electronic sensor for airflow measurement. A control unit to control the system function. The engine mechanical system. Notes: In the simple system model the following can be observed: Air flowing into the engine is measured by the air mass meter or pressure sensor. This is an input to the electronic control unit. The electronic control unit determines the correct amount of fuel to be added to this airflow to achieve the Stoichiometric air fuel ratio. The ECU opens the injectors just long enough to inject the correct amount of fuel (with this system we open the injectors at TDC of each crank revolution). When the throttle opens further, more air enters the engine. The airflow measured from the sensor increases. The electronic control unit opens the injectors for a longer period of time in order to maintain the Stoichiometric ratio. When the air flow changes we change the amount of fuel to maintain Lambda 1; more air more fuel, less air less fuel, always maintaining the air to fuel ratio at Lambda 1 (the Stoichiometric ratio). Fuel/Ignition Diagnosis & Repair Page 7.3

98 Mixture Formation This very Simple System Model is our starting point. Now we take the first step towards a more complete understanding of Porsche fuel systems. Our systems are digital and the following items are added: Computer Map Software program A map is a table of values (in this case injector opening times for different air flows). A program is a set of instructions that the computer in the engine control unit executes in sequence. Our digital computer performs the steps of the program one at a time. First look at the airflow amount. Second get the injector opening time from the injector opening time map. (base fuel delivery). Injector Duration Map #2 We can turn this into a three-dimension injector duration map like the one below if we show the injector duration as projecting upwards from the grid. Injector Duration Map #1 Third send a command to the injector operating circuit to open the injector for that amount of time. Back to step one, over and over (loop) as long as the engine is running. Our description of the injector opening time map in the example above is very basic, so let s take a more detailed look. We need to have engine speed as well as air flow in the map, because we need a different amount of fuel at low RPM for an airflow than we will need at a higher RPM for the same airflow. We need to add a speed sensor to the system model to accomplish this. When we add engine speed to our map, we end up with a grid like the injector duration (Map #2) with the upper right being wide open throttle and the lower left is idle. Lambda Map As you can see, there are a lot more data points in this map than there were in the first example. We can fine tune the fuel amount for each speed/airflow point. This will give the optimum mixture under all operating conditions. This system model works very similar to our model without engine speed. Get the air mass and engine speed from the sensors. Go to the map and retrieve the injector opening time (Ti or injector duration). Direct the injector final stage to open the injector for that amount of time. We have more precise mixture control when we add engine speed to our Ti map. Page 7.4 Fuel/Ignition Diagnosis & Repair

99 Mixture Formation When we change to a digital system, we not only have the ability to have the mixture at Lambda 1 regardless of the operating conditions, we also gain the ability to react to special conditions. For example: We have been operating at cruise with approximately 3000 RPM, Suddenly the RPMs fall, The throttle position is closed, We are in deceleration. We can have instructions in the fuel program turn the injectors off until the throttle is reopened, or idle RPM is reached thereby reducing emissions. There is one big disadvantage of operating at Lambda 1. If we analyze the Combustion by Products vs. Lambda 1 graph below we see three events. 1. CO is low at Lambda and increases as the mixture gets richer. 2. HC is low at Lambda and rises when the mixture moves either rich or lean (although not as rapidly as CO). 3. O 2 is low when mixture is rich. It begins to rise at Lambda and continues to rise as the mixture leans (a mirror image of CO). This third event will become very important later. There are also a number of conditions when we want the mixture richer than Lambda 1. For example: Cold start We want to heat the engine up, and, fuel doesn t atomize well when it is cold. Full throttle We want to provide extra fuel to reduce NO x. The heating that is required to evaporate the fuel lowers the combustion chamber temperature and reduces NO x. Digital systems are capable of processing a lot of data in very short periods of time. They are very precise as a result. It is easy to see that we can have a digital system match the mixture to the specific operating conditions. Notes: Combustion by Products vs. Lambda 1 The one gas that stands out is NO x, it peaks at Lambda 1. This is a problem since the amount of NO x that a vehicle can emit is limited by legislation. The HC and CO emissions are limited as well, but NO x is the largest concern. In order to sell vehicles in the USA, you must have some way to lower the NO x. The more efficient that the engine is, the more NO x it will produce. This is due to the fact that the atmosphere is about 78% nitrogen, and when you run nitrogen into a very hot combustion chamber (2500 F.), you oxidize that nitrogen producing NO x. So you must have some system to control NO x. Fuel/Ignition Diagnosis & Repair Page 7.5

100 Mixture Formation The solution we have adopted is the three-way catalytic converter. As you can see from the illustration below, three-pollutant gases enter in the three-way converter: 1. HydroCarbons (HC or unburned fuel) 2. Carbon Monoxide (CO this stuff will kill you if you breathe it) 3. Oxides of Nitrogen (NO x a neurotoxin) Platinum is a catalyst for oxidation of hydrocarbons (it promotes the combining of the hydrocarbons with oxygen while remaining unaffected). This is how we turn the combustion by product into H 2 O and CO 2 : You put two hydrogen atoms with one oxygen atom and you get water vapor. You put two oxygen atoms with one carbon atom and you get carbon dioxide. This chemical process is promoted by the surface of the platinum layer. It allows the atoms in the chemical compounds to recombine in the new combinations. These same gases do not exit. All that comes out of the converter are three non-polluting gasses: 1. H 2 O (water vapor) 2. CO 2 (a non poisonous gas that plants like) 3. N 2 (free nitrogen, plants like this as well). Here is how the catalytic converter works: The inside of the catalytic converter consists of a substrate of ceramic. In the case of Porsche catalytic converters after 1989, a stainless steel substrate. This substrate is coated with a very thin layer of platinum and rhodium (in late model converters we use palladium as well). This noble metal layer is deposited over a wash coat that increases the surface area of the layer, the layer can be very thin, it is the total surface area that is critical. One side effect of oxidation is heat; as the hydrocarbons oxidize, they heat up the catalytic converter. The converter is not completely efficient until it gets to a temperature above 1100 F. (600 C). We have to avoid any condition that would allow an excessive amount of hydrocarbons (like raw fuel) into the converter, since it will overheat the converter and damage it. In extreme cases it could cause a vehicle fire. Oxidation won t work on NO x (it is already oxidized), so we utilize the rhodium to reduce (remove oxygen from) the NO x. Each NO x we pull apart yields one free nitrogen atom. Depending on which compound of NO x is being broken up; one or more free oxygen atoms are produced (this is why it s an x, it means all the possible compounds). It is good that we produce free oxygen. We need it to oxidize the HC and CO. The rhodium catalyst works similarly to the platinum catalyst; its surface allows the NO x to break apart into its component atoms. This is a very good solution for reducing NO x and controls HC and CO emissions as well. Catalytic Components Page 7.6 Fuel/Ignition Diagnosis & Repair

101 Mixture Formation There is just one problem. If you look at the emissions after the Catalyst vs. Lambda 1 graph below you will see what the problem is. You have keep the air fuel ratio very close to Lambda. If you go a little rich, the HC and CO rise above the legal limit. If you go a little lean, the NO x goes right through the roof. As a result, you must have very good control of the mixture, close to Lambda won t do. You must be very close to Lambda. This takes us back to the simple system model. We need to improve our mixture control in order to be able to keep the air fuel ratio very close to Lambda. Emissions After Catalyst vs. Lambda 1 In the above illustration you will notice the change that allows us to achieve our goal is a sensor that measures O 2. We call it a Lambda sensor or oxygen sensor. As you observed in the Combustion by Products vs. Lambda graph, the oxygen content in the exhaust flow is directly proportional to air fuel ratio. This means that you can determine the air fuel ratio by looking at the oxygen content of the exhaust. Notes: Fuel/Ignition Diagnosis & Repair Page 7.7

102 Mixture Formation This is a different kind of input. The inputs we have talked about up until now give us information about engine conditions not directly controlled by the engine computer. The oxygen sensor tells us about a condition that we are controlling. We call this type of input a feedback input as it feeds back information about the systems output. So we change the way our system model works: Now we look at the air flow and engine speed, Go into the injector duration map, Get the Ti for that load speed point, Look at the oxygen sensor voltage, Modify the Ti a small amount to fine tune the mixture, Send the modified Ti to the injector final stage. This allows us to keep the mixture in the window that will keep our three-way catalyst working correctly to eliminate the NO x, HC and CO from our tailpipe emissions. As we mentioned before, the oxygen sensor generates a voltage. This voltage is directly proportional to air fuel mixture as we can see in the Sensor Voltage vs. Lambda graph. Sensor Voltage vs. Lambda The oxygen sensor operates on the principal of a galvanic oxygen concentration cell with a solid-state electrolyte; this means that it is a lot like a battery. Notes: Page 7.8 Fuel/Ignition Diagnosis & Repair

103 Mixture Formation Fuel Trim & Adaptive Mixture Control Systems The mixture control system has evolved over the last two decades into a self-adjusting system that learns and self adjusts. This system has three main levels of control: Main determination of injector duration for entire engine. Fuel trim system, adjusting mixture based on oxygen sensor voltage. OBD-II vehicles have two systems, one for each cylinder bank. Adaptation system adjusting fuel maps on long-term basis. To understand this system we need to examine these control levels in detail, so we will start at the beginning with a review of main injector duration determination. Fuel Trim System The next level of control is the fuel trim system. This system utilizes the oxygen sensor to modify the Ti that the main mixture control sends to the injector driver circuit. After 1996 (with OBD-II), this system divides the fuel system in half and each bank of the engine has it s own fuel trim system. These systems make a small change in the Ti based on the oxygen sensor voltage. When the voltage goes high, it indicates the mixture is rich and the control moves the mixture lean by reducing Ti. When the voltage goes low, it indicates the mixture is lean and the control moves the mixture rich by increasing Ti. Main Mixture Control The fuel mixture control program calculates the primary injector duration based on the load input from the mass airflow sensor or pressure sensor and engine speed from the speed and reference sensor. The program takes the present engine load and engine speed and retrieves an injector duration from the injector duration map. The program then modifies the injector duration based on the real time inputs (for example, if the engine coolant temperature is low, time is added to move the mixture rich). This injector duration (Ti) is then sent to the injector driver circuit and the injector is opened by this Ti. When we analyze the Voltage vs. Lambda graph we see three things: When the oxygen sensor voltage is in the area of 150 millivolts to 850 millivolts we are close to Lambda. In this area our three-way catalyst will operate at optimum efficiency. We will have good control of pollutant emissions. Fuel/Ignition Diagnosis & Repair Page 7.9

104 Mixture Formation You can see the relationship between oxygen sensor voltage and mixture control in the illustration below. This system however, has a limit to its ability to control mixture. If the deviation from Lambda is large enough to require a movement of more than plus or minus approximately 0.4 milliseconds, the system cannot correct the mixture. The system will default to open loop operation and a fault will be stored. Adaptation We will now examine fuel system adaptation (it is an addition to the fuel trim program software) and how it changes the fuel trim system. First we need to know how the Ti map is generated. This control system is referred to as the integrator. This control system is also known as short term fuel trim. It turns the oxygen sensor voltage into a decision to move mixture. It keeps the oxygen sensor voltage moving between 150 millivolts and 850 millivolts by adding or subtracting time from injector duration. For example: A normal idle Ti could be 2.4 milliseconds. A normal idle fuel trim might be milliseconds. 2.4 milliseconds +.24 milliseconds = 2.64milliseconds of Ti. The mixture is richer (adding Ti adds fuel). This would be a correction for a lean reading. The opposite would be true for a rich reading. The mixture moves up and down and the oxygen sensor voltage follows. The oxygen sensor voltage is always moving between 150 and 850 Millivolts. There are reasons for the movement between rich and lean: When the integrator (short term fuel trim) moves the mixture rich, it creates a lack of oxygen in the catalyst, this is needed for the reduction of NOx. When the integrator moves the mixture lean, it creates a surplus of oxygen needed for the oxidation of HC and CO. This is how a three-way catalytic converter is capable of meeting stringent emissions regulations and regenerating it self. The answer to this is; it comes from the development department at Weissach. Porsche fuel system engineers generate the Ti map with a test engine on a motor dynamometer. They run the engine in each load/speed range and then move the mixture rich and lean until the engine operates at Lambda 1. This gives us a Ti map for an ideal engine (The timing map is generated in the same way). This is a great method however, not all engines are made equal, and engines change as they age. So one fuel map (one size fits all) can t be perfect for all engines. Even if the map were perfect when the engine was new, it would not be perfect after the engine has been run 100,000 miles. We have a special addition to the fuel mixture software, it is called adaptation (long term fuel trim). Here is how it works. The adaptation program monitors the mixture control system for a time period. For example ten minutes; let s say that during that time period the integrator has had to add.25 milliseconds to the Ti for the entire time. We then know that the Ti map is too lean by.25 milliseconds. The adaptation program adds.25 milliseconds of time to the fuel map. When the fuel trim system gets a Ti from the fuel map, it only needs to make a small correction since the Ti map has been adjusted to fit the engine that it s in control of. The adaptation program has no hardware or moving parts. It is a system that exists only as lines of code in the fuel trim system software. Page 7.10 Fuel/Ignition Diagnosis & Repair

105 Mixture Formation Before we added adaptation to our fuel mixture control system; it was necessary to manually adjust the idle CO by disconnecting the oxygen sensor (to put the system into open loop) and adjusting an air bypass around the airflow sensor. With adaptation we no longer need a CO adjustment. The system automatically adjusts itself, compensating for differences between engines caused by manufacturing tolerances and other conditions (air leaks, wear in internal parts ). Why bother with adaptation? We already have the integrator. It can just keep adding the.25 milliseconds of Ti without changing the map. The reasons we need adaptation are: We do not always operate in closed loop. If we do not adapt the Ti map we will not have the needed correction when we operate in open loop. The fuel trim system works much better when it is operating in the center with the same amount of correction available in both the rich and lean directions. Adaptation Numbers Another feature of digital engine management is the ability of the engine management computer to communicate with a diagnostic system. Data such as; inputs, outputs and other information from the operation of the control systems can be monitored. Porsche has had a series of testers: 9268, 9288, PST2 and now PIWIS. With the system tester we can see a large number of values from the fuel system. One of these is how much the mixture adaptation system has changed the Ti map. We can learn to use this information for diagnostics. Porsche adaptation systems have different ranges of control: One range is adaptation for idle, RKAT (before model year 2000 we called it TRA). The Idle range as we have described in our example adds or subtracts injection time in response to oxygen sensor input. Another range is adaptation for the load range FRA (in the latest models the FRA is divided into an upper and lower range FRAO and FRAU). The load range is slightly different. It does not add and subtract time from the Ti; it multiplies the Ti. For example: If you multiply a Ti of 2.4 ms X 1.1 = 2.64 milliseconds. If you multiply a Ti of 2.4 ms X 0.9 = 2.16 milliseconds. By multiplying the Ti in the load range we are able to make large changes easily. Multiplying isn t as good for the idle range where we need to make small changes. In addition, in 1996 with OBD-II we divide the fuel trim system into two systems. One system for cylinder bank 1 3 One system for cylinder bank 4 6 or One system for bank 1 4 One system for bank 5 8 When we divide the fuel trim system in half, there isn t much difference in how the fuel trim system works. There are just twice as many adaptation numbers and oxygen sensors. Our digital fuel mixture control has a fuel control program operating in a microcomputer and utilizing maps for control. We talked about the injector duration (Ti) map in the digital system section. There are several other maps, for example: 1. The evaporative emissions purge valve map. 2. The idle control map. 3. Ignition control map. 4. Fuel pressure control map. With a digital microcomputer we have the possibility to add new features to the software. A couple of examples would be: 1. VarioCam 2. Resonance Intake System We just add the hardware to the engine, and instructions to the program to drive the hardware (output). There can also be features that have no hardware. They only exist as lines of code in the fuel system software. These systems will be discussed in a separate section. Fuel/Ignition Diagnosis & Repair Page 7.11

106 Mixture Formation Digital Motor Electronic (DME) We have described the basics of digital electronic ignition and fuel systems. Now we will discuss how the three basic elements fuel system, ignition system and digital microcomputer are combined in one system Digital Motor Electronic. First think about the inputs to ignition control. Load Speed Throttle position Engine and ambient temperature They are the same as the inputs for fuel control. Speed Throttle position Engine and ambient temperature We add the oxygen sensor for fuel control but otherwise the same inputs for both systems. Outputs A square wave is also sent to the injector. The period of the square wave is injector duration (Ti) and the falling edge of the waveform is the beginning of injector operation. This is timed to TDC on the banked injection systems we used up until In 1989 Porsche begin to use sequential injection where you only operate the injector when the intake valve is open, so we time the injection point to the over lapping TDC. The bottom line is that the inputs and outputs for fuel and ignition control are either the same, or very close to the same for both systems. So combining them in one control unit just made sense. Adding the microcomputer was the only way you can have data maps stored in memory (for example injection duration and ignition timing maps), and a program that utilizes them to control engine management systems. This achieved exceptional output and performance while maintaining the emissions levels required by law. A square wave is sent to the ignition system where the period of the wave is dwell; and the relationship between the rising edge of the square wave and crankshaft position is ignition timing. Notes: Page 7.12 Fuel/Ignition Diagnosis & Repair

107 Mixture Formation Injection Method Gasoline Engines Intake Manifold Injection Fuel injection systems with intake manifold injection (MPI Multi Point Injection) are characterized by the fact that the air/fuel mixture is formed outside of the combustion chamber, i.e. in the intake manifold. This is referred to in this context as external mixture formation. The fuel injector injects fuel earlier into the intake duct upstream of the intake valves, which are still closed. Mixture formation takes place partly in the intake duct and partly in the combustion chamber. During the intake process, the air/fuel mixture is drawn through the open intake valve into the cylinder. On vehicles with MPI, fuel is deposited on the intake manifold, valves and cylinder walls and as a result, this fuel is no longer available for combustion. This is primarily the case when starting the engine at low temperatures and necessitates a greater quantity of fuel than is required for combustion. Direct Fuel Injection (DFI) Fuel is injected directly into the combustion chamber by electromagnetically operated fuel injectors. One fuel injector is assigned to each cylinder. Mixture formation takes place in the combustion chamber. Only the combustion air flows through the open intake valve during the intake stroke. This allows two totally different operating modes: Homogenous Mode This mode is used when the engine is warm. In homogenous mode, just like with external mixture formation, there is a homogeneous mixture in the entire combustion chamber and all the fresh air available in the combustion chamber takes part in the combustion process. Stratified-Charge Mode For starting the engine and for the warm-up phase following a cold start, the injection modes, which you will become familiar with from DFI engines, are used to produce specifically inhomogeneous mixture distributions in the combustion chamber. An injection just before the top dead center of the compression phase ensures extremely reliable engine start performance for highpressure stratified charge injection. At the same time, the necessary enrichment requirement and the associated emissions in the start-up phase are drastically reduced. After a cold start, multiple injection during the intake and compression strokes combined with a very late timing angle is an efficient measure for heating the 3-way catalytic converter quickly. Thermodynamics With DFI Engines Direct fuel injection goes a long way towards meeting the objectives that were written into the performance specifications for new generations of engines. The homogeneous DFI combustion process used in these engines is therefore the ideal solution as far as the requirements are concerned. Reducing fuel consumption Increasing power Improving dynamic engine response Suitability for worldwide gasoline fuels Cooling of the cylinder s fresh charge by the heat required for evaporating the fuel in the combustion chamber increases the charge density and reduces the knocking tendency. This results in significantly improved specific full load values and a higher compression ratio than are possible with intake manifold injection (MPI). Based on this, a homogeneous DFI concept also offers enough potential for reducing fuel consumption. In addition to improved thermodynamic efficiency as a result of the higher compression ratio, a downsizing effect thanks to similarly higher specific full load values is also useful as predefined target values for torque and power or a required, higher performance with the same or an even lower stroke volume are possible. Direct injection into the combustion chamber improves the dynamic responsiveness of the engine as there is no significant wall film on the surfaces of the intake duct. This allows precise cyclical metering of the required fuel quantity, even for highly dynamic driving. Fuel/Ignition Diagnosis & Repair Page 7.13

108 Mixture Formation The main objective is to achieve a mixture composition adapted specifically to the respective operating and load states of the engine through corresponding fuel injection and mixture formation. This provides the perfect solution for meeting the various demands relating to economy, power, vehicle handling and emissions. Porsche used direct fuel injection (DFI) for the first time in the new generation of Cayenne engines in model year With direct fuel injection, the fuel is injected directly into the combustion chamber at a pressure of up to 1740 psi (120 bar) so that mixture formation takes place almost entirely in the combustion chamber. This offers numerous advantages compared to intake manifold injection. The main characteristics of direct fuel injection are as follows: Homogeneous concept, stoichiometric ratio Optimum emission control thanks to three-way catalytic converter Use of the various-quality fuels throughout the world High-pressure fuel injector with conical spray (hollow cone swirl injector) Fuel injector is positioned at the side next to the intake duct Piston recess for a stratified mixture formation when starting the engine and during the catalytic converter warm-up phase (engine-specific) DFI-specific diagnostic functions in the PIWIS Tester All high-pressure components are adapted to the fuel requirement of the respective engine. The fuel jet is swirled inside the injector (rotation around the longitudinal axis). This rotation forms a cone-shaped cloud of fuel. The fine atomization this creates enables quicker evaporation of the fuel. The fuel evaporation process takes the required heat energy from the air, thereby cooling the air. This reduces the cylinder charge volume and additional air is drawn in through the open intake valve, which in turn improves the cylinder charge. The reduced temperature level also helps to meet the prerequisites for higher compression since knock sensitivity of the engines has been improved. This ultimately improves the efficiency of DFI engines. The spray and cone angles of the hollow cone swirl injectors have been optimized to achieve ideal homogenization across the entire operating range. Page 7.14 Fuel/Ignition Diagnosis & Repair

109 Mixture Formation Piston Recesses in DFI Engines Engine Operating States Engine operating states are primarily characterized by the generated torque and the engine speed. Of significance are the operating states with a high load or engine speed dynamics, since they have special requirements in terms of mixture formation (e.g. wall film formation and evaporation). The various operating states are as follows: Start During the entire start process, there is a special calculation of the injection volume and the start of injection. On vehicles with intake manifold injection (MPI), an increased injection volume, which is adapted to engine temperature, creates a film of fuel on the wall of the intake manifold and cylinder and meets the increased fuel requirement during the engine start-up phase. Vehicles with DFI have special injection strategies. The piston recesses are important for high-pressure stratified-charge injection and for dual injection during the catalytic converter warm-up phase. They enable late injection in order to achieve an ignitable air/fuel mixture around the spark plugs in the case of late ignition. Quick Start An ignition output can only occur if the cylinder that is currently in the compression stroke is detected based on the Hall sender signal. In the worst case scenario, a complete camshaft revolution is necessary in order to detect the compression stroke of cylinder 1. The start process can be speeded up with the help of overrun detection. New systems now have a differential Hall-effect sensor on the crankshaft, which enables a so-called quick start. Notes: Fuel/Ignition Diagnosis & Repair Page 7.15

110 Mixture Formation After-start During the after-start (phase after the end of starting), the increased injection volume is reduced further depending on the engine temperature and the time after the end of starting. The after-start phase moves smoothly into the warm-up phase. Vehicles with DFI have special strategies, even for the after-start and catalytic converter warm-up functions. Warm-up The warm-up phase can involve different procedures depending on the engine and emissions concept. Drivability and the exhaust emissions and fuel consumption measurements are decisive factors here, whereby one central criterion is the quick availability of the emission control system. There are essentially two concepts: Lean warm-up with late ignition and injection timing and Secondary-air injection or high mass air flows Start Phase of DFI Engines High-pressure stratified charge injection is used in DFI engines in order to optimize cold starting with regard to fuel consumption and emissions. In this process, injection into the specifically shaped piston recess takes place once shortly before the end of the compression stroke, creating stratification around the spark plug, which generates an ignitable mixture. The piston recess ensures that the injected fuel is channeled directly to the spark plug. This reduces both the amount of fuel required and the emissions compared with intake manifold injection. injection of fuel takes place during the intake stroke and the second injection of fuel occurs into the piston recess when the intake valves are closed, just before the end of the compression stroke. The air/fuel mixture is ignited very late, thereby increasing the exhaust-gas temperature. Consequently, emissions are reduced during the warm uphase. Engine at Operating Temperature Fuel is injected only during the intake stroke when the engine is at operating temperature. Single injection is used at idle speed, in the partial load range and at high engine Speeds Multiple Injections in DFI Engines Multiple injections occur during the intake stroke in the upper load range up to medium engine speeds (approx. 3,500 rpm). Dual injections or even triple injections are used depending on the engine, load and engine speed. The quantity of fuel needed for combustion is shared between several successive injection processes. In the upper load range, these injections take place during the intake stroke (synchronous intake injection) when the intake valves are open, thereby ensuring improved homogenization for saving fuel. Injection Strategies of DFI Engines Injection time and injection timing The injection time of DFI engines under real engine operating conditions is between approx. 0.5 ms (at zero throttle, idle speed) and 6 ms (at full throttle). When starting the engine, fuel is only injected once into the compression stroke on most DFI engines. On the Cayenne V8 DFI engines from MY 2011 onwards, triple injection is also used for the first time depending on the starting temperature (< 140 F./60 C). Catalytic Converter Warm-up Phase of DFI Engines Once the high-pressure stratified charge injection starts the engine, the engine management system switches to the catalytic-converter warm-up phase. In this operating state, a dual injection system helps to bring the catalytic converter to the temperature required for optimal conversion of pollutants as quickly as possible by increasing the exhaust emissions temperature. To this end, the first Page 7.16 Fuel/Ignition Diagnosis & Repair

111 Early injection during intake stroke Mixture Formation Higher engine efficiency due to improved homogenization Greater soot formation when the fuel spray hits the piston surface Late injection during intake stroke Less time for mixture homogenization Reduced engine efficiency and greater soot formation This graph shows the effect of injection timing and injection time on engine efficiency and soot emissions on the Cayenne V8 S DFI engine at 3,500 rpm and at full throttle with single fuel injection. 1 - Duration of injection 2 - Start of injection 3 - End of injection 4 - Crankshaft position 5 - Top dead center (TDC) 6 - Bottom dead center (BDC) 7 - Engine torque in Nm 8 - Soot formation Notes: Fuel/Ignition Diagnosis & Repair Page 7.17

112 Mixture Formation The following graphs show examples of the injection strategies of the Porsche V8 DFI engines as of MY 2008 thru present MY. Fuel injection in stratified-charge mode (only when starting the engine and heating the catalytic converter) Fuel injection in homogeneous mode (when the engine is at operating temperature) When the engine is at operating temperature, fuel is only injected during the intake stroke and the engine therefore runs in homogeneous mode (in other words: there is a homogeneous air/fuel mixture in the cylinder). 1 - Top dead center (TDC) 2 - Bottom dead center (BDC) 3 - Crankshaft position 4 - Piston position 5 - Injection 6 - Ignition 7 - Intake stroke 8 - Compression stroke Starting the engine (top graph) Single injection at the end of the compression stroke while starting the engine results in a concentration of fuel around the spark plug (stratified operation) and can reduce enrichment and thus emissions during start-up. Heating the catalytic converter (lower graph) The stratified mixture produced by dual injection during the intake phase and at the end of the compression stroke enables a later timing angle in order to heat the catalytic converter faster. 1 - Top dead center (TDC) 2 - Bottom dead center (BDC) 3 - Crankshaft position 4 - Piston position 5 - Injection 6 - Ignition 7 - Intake stroke 8 - Compression stroke Single injection (top graph) Single injection is synchronized with the intake stroke (intake valves open) practically over the engine s entire operating range. A short single injection occurs at idle speed and at low engine load. A long single injection occurs at high rpm and at high engine load. Dual injection (lower graph) Dual injection during the intake stroke improves mixture formation, engine efficiency and the stability of the combustion process at an engine speed of up to 3,500 rpm and at a high engine load. Fuel injection is no longer interrupted at a high engine load above 3,500 rpm and as a result, the engine is operated with a correspondingly long single injection of fuel in this case. Page 7.18 Fuel/Ignition Diagnosis & Repair

113 Mixture Formation Transition A change in engine load and/or engine speed involves either an acceleration/deceleration or deceleration fuel cutoff/resumption. During acceleration, a fuel quantity that is required in addition to the wall film is injected in order to prevent the mixture from becoming lean during the acceleration process. When the load is reduced, the fuel quantity stored in the wall film is released again. As a result, the injection time must be reduced for the deceleration process in accordance with the stored fuel quantity. During deceleration fuel cutoff, the torque flow on vehicles with an electronic throttle can prevent a jump in torque during the transition to overrun as a result of switching off the injection pulses. After the resumption speed is exceeded, the necessary wall film is formed using an additional fuel quantity during the first injection pulses. Lambda Coordination To meet the required engine torque and optimize engine efficiency, the actual combustion process must be carried out with an almost stoichiometric air/fuel ratio. A stoichiometric air/fuel ratio is achieved when the air mass (ml) in the combustion chamber is exactly right for burning all the available fuel mass (mk). For commercially available fuel, this produces a stoichiometric mixture ratio of ml/mk The air ratio of lambda λ or even the lambda value now describes the ratio between the real air mass and the air mass required for stoichiometric combustion. This means that stoichiometric combustion takes place when λ = 1. The lambda value therefore describes the composition of the air/fuel mixture in the combustion chamber. The DME control unit is responsible for calculating the fuel mass to be injected, whereby different influencing factors must be considered. Anticipatory Mixture Control The fuel proportioning anticipatory control system is responsible for calculating all factors, which influence the effective mixture composition in the combustion chamber in advance in such a way that engine operation with a required lambda (normally lambda λ = 1) is guaranteed as often as possible. The individual influencing factors are taken into account during calculations in the DME control unit by introducing related correction factors or relevant additive values. The following correction factors are available: Basic factor The basic factor is a basic value, which determines the basic setting of the engine for operation with λ = 1. This factor is used to compensate for deviations between the theoretical, relative fuel mass (rk) for the engine at operating temperature and the relative fuel mass that is actually required. Start correction factor A differentiation is essentially made here between cold starting, repeated cold starting, warm starting and repeated warm starting. Optimum adaptation of the Start correction factor to the relevant operating point of the engine is only achieved using this differentiation. After-start correction factor The objective here is to provide the combustion chamber with a stoichiometric mixture in the engine operating phase after starting. The excess or reduced quantity correction can be set here using load- and temperaturedependent maps, which are essentially dependent on the engine start temperature, the intake air temperature, the time that has elapsed since switching off the engine and the current air mass. Different quality fuels, i.e. the composition of the fuel mixture, also have a significant influence on combustion in the after-start phase. Given this, the injection mass must also be adapted to the fuel quality here. Warm-up and Lambda specification correction factor This correction factor corrects fuel proportioning errors, which can occur during the engine warm-up phase. It is only calculated using maps depending on the current engine temperature, the temperature during start-up, the engine speed and the air charge (rl). Fuel/Ignition Diagnosis & Repair Page 7.19

114 Mixture Formation Load change correction factor This correction factor is used to increase or reduce the injected fuel mass during a load change in order to ensure that λ always equals 1. Two-bank system correction factor On engines with two cylinder banks (Boxster/Cayman, 911 Carrera, 911 Turbo, Cayenne/Panamera V6/V8), different flow conditions can mean that the two cylinder banks are supplied with different air masses, which can result in different lambda values in the individual combustion chambers. It is necessary therefore to carry out a correction of bank 1 and bank 2 in accordance with engine speed and total air charge (rl). Oxygen Sensor Closed-loop Control The purpose of oxygen sensor closed-loop control is to adjust the mixture in the engine combustion chambers so that the catalytic converter is working at its optimum and therefore the emissions limits are adhered to. Oxygen sensor closed-loop control therefore has to always keep the exhaust gas air ratio at the optimum operating point for the catalytic converter. To ensure that the conversion rate for all three pollutant components (CO, HC and NOX) is as high as possible in systems that use a three-way catalytic converter, the pollutants must be present in the same chemical balance. This requires a mixture composition in the stoichiometric ratio with lambda = 1.0. The window in which the air/fuel ratio can vary is thus very small. Control via fuel proportioning alone is not sufficient. Deviations from a certain air/fuel ratio can be detected and corrected by the control circuit formed by the oxygen sensors. The control principle is based on measuring the residual oxygen content in the exhaust gas. The residual oxygen content is a measure of the composition of the air/fuel mixture supplied to the engine. The oxygen sensor closed-loop control in the control unit must then adjust the mixture composition accordingly from the signal provided. The control therefore depends greatly on the properties of the oxygen sensor. Stereo Oxygen Sensor Closed-loop Control With stereo oxygen sensor closed-loop control, both cylinder banks have a separate oxygen control circuit in order to determine and meter the best air/fuel mixture (for each cylinder bank). To check the function of the catalytic converters, the left and right exhaust tracts in the current systems each have an oxygen sensor upstream and downstream of the catalytic converter. Notes: Page 7.20 Fuel/Ignition Diagnosis & Repair

115 Mixture Formation Oxygen Sensor Closed-loop Control Upstream of Catalytic Converter As described earlier, oxygen sensor closed-loop control must ensure that the optimum air ratio is always available in the exhaust gas. For this purpose, oxygen sensor closed-loop control (for each cylinder bank) only changes the fuel mass to be injected. The air mass in the combustion chamber, i.e. the cylinder charge and timing angle, is not changed. Oxygen sensor closed-loop control now intervenes in fuel proportioning using the variables lambda controller (for continuous mixture control) and by adaptively changing the fuel mass using the mixture adaptations (RKAT at idle speed, FRA or FRAU and FRAO under load). Essentially, the lambda controller variable is the control factor of the oxygen sensor closed-loop control system and the variables FRA and RKAT are adaptive corrections designed to allow anticipatory control of the mixture that is as close to ideal as possible. The faster the control counteracts a shift in the air ratio using the lambda controller, the better the quality of the control. Since the fuel is always injected earlier and the oxygen sensor is not located directly in the engine s combustion chamber, there will be a minimum time lapse, which depends on the time lag of the controlled system. Essentially, the time lag includes the DME control unit s calculation time, the length of time for which the fuel is temporarily stored until it is drawn in, the delay time in the cylinder, the gas travel time in the exhaust system and the oxygen sensor s response lag. The time lag therefore depends on the engine speed and engine load. To achieve a constant amplitude of the lambda controller s vibration, the change in the lambda controller must be adapted. In addition, a jump in the lambda controller is introduced when the mixture changes from rich to lean and from lean to rich in order to shorten the vibration period. Circulation Control Downstream of Catalytic Converter The catalytic converter efficiency must be continuously monitored as per the OBD II regulations. A second oxygen sensor (jump-type sensor) must be installed downstream of the catalytic converter for this. Comparing the sensor signals upstream and downstream of the catalytic converter permits statements about the efficiency of the catalytic converter. In terms of improved oxygen sensor closed-loop control, this second sensor can also be used to correct the actual control. Since the sensor downstream of the catalytic converter is better protected from harmful exhaust components, signs of ageing on the first sensor can be more effectively corrected. Two-point Oxygen Sensor Closed-loop Control Wiith Oxygen Sensor LSH or LSF When a two-point oxygen sensor is used upstream of the catalytic converter, only qualitative statements about the exhaust gas composition, i.e. mixture formation finally takes place; can only be classified as rich (λ < 1) or lean (λ > 1), can be made. Optimum control of the exhaust gas composition can therefore only be achieved by constant variation around the lambda = 1 range. Illustration of dynamic two-point oxygen sensor closed-loop control with the typical vibration behavior Graph 1 shows the ideal output signal of the two-point oxygen sensor. Graph 2 shows the vibration behaviour of the lambda controller (FR). To shift the control towards rich, a switchover delay with maximum value limitation is introduced as shown in Graph 3) Fuel/Ignition Diagnosis & Repair Page 7.21

116 Mixture Formation Due to the unequal sensor characteristics during shifts from rich to lean and from lean to rich, the symmetric control behavior shown in section b) results in a slightly leaner exhaust gas mixture. However, since the catalytic converter's optimal efficiency level is in the range λ , the control system must counteract this effect. By introducing a jump-back on one side in the range λ < 1, the mean value of the lambda controller remains in the rich range. The dynamics of the lambda controller can be retained by introducing a maximum value limitation. Graph 3 shows the change in the adapted controller factor (FR). The limitation means that the control amplitude does not increase so that a constant, rapid counter control can take place. The lambda controller makes the mixture richer at a sensor voltage of < 450 mv and leaner at > 450 mv is the lambda controller mean value 0.75 means that the lambda controller makes the mixture lean (because mixture is too rich) 1.25 means that the lambda controller makes the mixture rich (because mixture is too lean) Continuous Oxygen Sensor Closed-loop Control With Broadband Oxygen Sensor (LSU) Broadband oxygen sensors are only installed upstream of the catalytic converter (for the first time on the 911 Turbo 996). It has an oxygen pump cell and needs a special control circuit in the DME control unit. When a broadband oxygen sensor is used, the air ratio of the exhaust gas can be determined directly from the pump current (see diagram). This facilitates direct, continuous control of the mixture composition. In contrast to the jump-type oxygen sensor, which merely indicates whether the engine mixture is lean or rich, the continuously measuring broadband oxygen sensor assesses precisely how lean or rich the mixture is (from lambda = 0.7 to lambda > 2) Lambda value 2 -- Pump current in ma Continuous determination of lambda values results in smaller control amplitudes, which are decisive for the high quality of the control. The broadband oxygen sensor also allows control in ranges other than λ = 1, as is required, for example, for secondary-air injection into the exhaust pipe during the engine warm-up phase. In this case, control is always performed based on a predefined combustion chamber lambda value, so that the mixture does not become too rich when the air is injected. Continuous oxygen sensing also requires a continuous lambda controller, which is designed as a PID controller and whose frequency range depends on the engine speed and the relative air charge. The lambda controller in the DME control unit corrects the mixture for each cylinder bank depending on the voltage signal from the oxygen sensor upstream of the catalytic converters. This lambda controller for each cylinder bank can be read out from the actual values in the DME control unit. Mixture Adaptation In the Mixture formation subsystem, the fuel mass relating to the air charge is calculated in homogeneous mode with a defined air/fuel ratio of 14.7 : 1 and the required injection time and the most efficient injecting timing is determined from this. Adaptation of Anticipatory Mixture Control As described earlier, oxygen sensor closed-loop control corrects the amount of fuel injected based on the measured values from the oxygen sensors. The time delay that occurs here between measurement and control intervention is mainly determined by the gas travel time from the fuel injector to the oxygen sensor. Page 7.22 Fuel/Ignition Diagnosis & Repair

117 Mixture Formation When a new engine operating point is reached, there will be greater concentrations of pollutants in the exhaust gas if fuel injection anticipatory control is not performed correctly because oxygen sensor closed-loop control can only compensate for possible changes after a time delay. Very precise tuning (anticipatory control) of the mixture composition is therefore needed to minimize the pollutants in the exhaust gas. Ageing of fuel injectors and oxygen sensors as well as changes in the fuel quality mean that the initially optimum data for anticipatory control can result in an inaccurate mixture composition. Inaccurate anticipatory control then results in high concentrations of pollutants when the engine operating point is changed. Such effects can be avoided by continuously adapting anticipatory control. The task of continuously and automatically adapting anticipatory control is performed by mixture adaptation. The aim of mixture adaptation is to compensate for long-term changes in the system. Shortterm influences must not be included. Mixture adaptation is therefore prevented during the active fuel tank ventilation phases. Mixture adaptation can influence the fuel mass to be injected using the multiplicative variable FRA for the load ranges or the additive variable RKAT (or TRA in M 5.2 systems) for the idle speed range. The following fault causes can be differentiated for conspicuous mixture adaptations: Fault when the mass air flow in the idle speed range is low, e.g. unmetered air at the intake manifold (additive fault affecting range 1/RKAT or TRA). Fault in the high load range, e.g. incorrect mass air flow signal (multiplicative fault affecting range 2/FRA or FRAU/FRAO). To better narrow down the various sources of faults, an engine speed/load map is divided into the specific subranges. A specific fault cause is assigned to each subrange. The next illustration shows a possible division of the engine speed/load map into sub-ranges. If the lambda controller mean value differs significantly from 1.00, the fault is attributed to the corresponding range. The adaptive correction value is then adjusted until the lambda controller mean value is 1.00 again. A new adaptation value can only be learned here when the engine operating point is actually in one of the defined ranges. However, the adaptation corrections are effective in the entire engine speed/load range. Of course, other sub-ranges can be introduced for clearer differentiation in order to refine and improve the adaptation. But even these sub-ranges are only included in order to influence the mixture composition using the multiplicative variable FRA and the additive variable RKAT/TRA. Notes: Fuel/Ignition Diagnosis & Repair Page 7.23

118 Mixture Formation The adaptation values are stored in a volatile memory for Bosch systems. If the power supply is interrupted and when the fault memory is erased, the adaptation values are reset to the mean value and the adaptation starts again in the predefined time sequences. If the adaptation values exceed certain limits, a fault is entered in the fault memory. Before entering the fault, however, the diagnostic system must make sure that both adaptation ranges were selected at least once (both ranges always influence the entire map). The fuel tank ventilation phases and mixture adaptation phases alternate when the engine is running at operating temperature and while driving. During the fuel tank ventilation phases, which last approx. 300 to 600 seconds, the mixture control unit is working, but no adaptation takes place. This is followed by a mixture adaptation phase lasting approx. 100 seconds (with the tank vent valve closed). The requirement is adapted to the corresponding range (RKAT, FRAU or FRAO) depending on the intake air mass during the adaptation phase. The mixture adaptation close to idle speed range RKAT or TRA can also be adapted at idle speed in the workshop. The mixture adaptation range FRA or FRAU/FRAO is only adapted for the corresponding air mass while driving. With the systems ME 7.8 and ME 7.1.1, the load adaptation ranges FRAU and FRAO are displayed apart from the mixture adaptation range RKAT. 1 - Engine load in % 2 - Engine speed in rpm RKAT - Mixture adaptation close to idle speed range, mass air flow of approx. 12 to 32 kg/h, new systems: 0.0 +/ %; older systems: 0.0 +/ % FRAU - Mixture adaptation in lower load/engine speed range or partial load, mass air flow of approx. 32 to 220 kg/h, control range: 0.70 to 1.30, mean value: 1.00 FRAO - Mixture adaptation in upper load/engine speed range, mass air flow of more than 220 kg/h; control range: 0.70 to 1.30, mean value: 1.00 If the lambda controller must correct a value that is significantly different from 1.00, the corresponding mixture adaptation range will be corrected during the next mixture adaptation until the lambda controller moves back to around the mean value Mixture adaptation in newer systems is divided into the three ranges RKAT, FRAU and FRAO depending on the intake air mass. Page 7.24 Fuel/Ignition Diagnosis & Repair

119 On-Board Diagnostics (OBD II) Subject Page On-Board Diagnostiocs OBD-1 (Comprehensive Component Monitor) Monitors Run Continously Misfire Monitor Engine Roughness Detection Misfire Control Monitor Monitors Run Once Per Key Cycle Fuel Tank Ventilation Monitor Tank Venting Tests Catalyst Monitor General Notes P-Codes Fuel/Ignition Diagnosis & Repair Page 8.1

120 On-Board Diagnostics (OBD II) On-Board Diagnostics (OBD II) The diagnostic functions that are integrated in the DME control unit check the system (control unit, sensors, actuators, and wiring) for malfunctions and faults, store any faults that are detected in the data memory and activates backup functions if necessary. The OBD system was developed in accordance with US legislation for monitoring all components and systems that influence vehicle emissions. Porsche Emission Control Systems and OBD-II As we discuss the emissions control systems on Porsche vehicles we will discover that these systems are enfolded by the OBD-II system, and when we study the Porsche OBD-II system we are studying Porsche emissions controls in a comprehensive manner. Examining these systems inside the framework of OBD-II as a complete system will organize and simplify our study of emission systems. So how does the malfunction indicator light/comprehensive component monitor work? Well the first element is the digital computer which is the heart of the DME control unit without a digital computer we could not have on-board diagnostics. The second element is the diagnostic program that is run by the computer without software the computer can t perform any function. These two elements, the digital microprocessor and the software program that it runs are what is really unique about digital engine management, and what gives digital systems the ability to self diagnose. Let s take a look at how the system would diagnose a simple sensor circuit the engine coolant temperature sensor. This will allow us to understand how these monitors work. We will divide OBD-II into four topics: I. OBD-I - Comprehensive Component Monitor II. Dynamic Monitors - Monitors run continuously - Monitors run once per key cycle III. Malfunction Indicator Light and Fault Management IV. P-Code System By dividing the emission system into these four subjects we will have a clear and understandable description of Porsche emission systems and how they operate. The first two subjects; Comprehensive Component Monitor and Dynamic Monitors contain several examples of the physical systems of Porsche emissions control and how they are monitored. The other two topics are directly related to OBD-II fault management and legislative requirements. OBD-I (Comprehensive Component Monitor) As you can see in the diagram above, the sensor is in series with the voltage regulator. It is an NTC resistor. This means that as temperature increases, the resistance of the sensor decreases. Above the sensor, the voltage regulator in the control unit supplies a five volt reference, and below it is connected to the sensor ground circuit. OBD-I was introduced to Porsche vehicles in The system consisted for the most part as software in the DME control unit, the only hardware involved was the light in the instrument cluster. With OBD-I, if an emissions related component failure is detected by the diagnostic program a check engine warning light is illuminated. Page 8.2 Fuel/Ignition Diagnosis & Repair

121 On-Board Diagnostics (OBD II) The microcomputer is really just a complex adding machine. All the data it deals with must be converted into numbers that can be transmitted as 0 or 1. The computer will only do what its program tells it to do. This program is just a list of commands that the microcomputer executes one after the other. If the commands are not written correctly the microcomputer will execute the incorrect command it does exactly what the commands in its program tell it to do. So the better the diagnostic program is written the better the diagnosis. Here is an example of how a diagnosis of an engine temperature sensor might be written: NTC Resistor Chart Showing Temperature Versus Resistance. This will cause the voltage drop across the sensor to decrease as temperature increases. The voltage drop has a finite range. It cannot be at 0 because the sensor can be a very low resistance, but can never be without any resistance. In addition, it cannot be at five volts because the sensor can have a very large resistance, but not an infinite resistance (an infinite resistance is a open circuit). As we can see in the system diagram, the microcomputer is separated from the sensor circuit by the analog to digital converter. The microcomputer must be separated from the analog circuit due to the voltage level that it operates at. The microcomputer operates at micro amps and volts and the voltages and amperages in the analog circuit would damage the microcircuit. In addition, the digital computer cannot process an analog signal. The actual voltage must be converted into a binary number for the microcomputer to process it. As you can see, if there is no problem, the program proceeds to the next test. If a fault is found, it is stored in the fault memory and the check engine light is turned on and then the next test is preformed. When the program has run completely through, it starts over and runs again. The program will continue this repetition over and over the entire time that the engine is running. Notes: Fuel/Ignition Diagnosis & Repair Page 8.3

122 On-Board Diagnostics (OBD II) This program performs circuit tests as in our example on all of the circuits in the engine management system, and in addition, it performs rationality checks on the sensors. For example; if the voltage of the temperature sensor doesn t move a certain amount in a given time, it is diagnosed as defective, even though it is within its range. We know that the engine temperature must rise if the engine is running. The misfire monitor detects misfire by monitoring the acceleration of the crankshaft that occurs when a spark plug fires and the combustion process forces the piston down the cylinder, thereby accelerating the crankshaft. The system utilizes the speed and reference sensor that is part of the engine management system to detect the acceleration of the crankshaft caused by the combustion process. This diagnostic system program runs in the background of OBD-II and is one of the diagnostic tests that are run continuously. All components of the system are checked by the Comprehensive Component Monitor for: shorts to ground shorts to power - open circuits rationality (is the value measured by the sensor a value possible for a correctly operating system). With OBD-II the malfunction indicator light may or may not be turned on immediately when a fault is detected. It will be stored in memory and the light is turned on only when the OBD-II fault management system has determined the fault is legitimate. This usually will take two key cycles and the fault must be present for a time frame set by the diagnostic program. Monitors Run Continuously Examples: 1. Misfire Monitor 2. Mixture Control Monitor Misfire Monitor The misfire monitor detects any condition that causes the mixture in the combustion chamber not to ignite. When the hydrocarbons (fuel) in the combustion chamber do not ignite, they pass down the exhaust system into the catalytic converter where they cause overheating that will damage the converter. This is due to the oxidation process that takes place in the converter. Oxidation (burning) of the hydrocarbons is promoted by the platinum and rhodium catalyst. Relatively small amount of hydrocarbons that are normally in the exhaust flow will not overheat the converter. This makes it essential that misfire conditions be detected by the OBD-II system and indicated to the driver by the malfunction indicator light. 1 Bar magnet 2 Sensor housing 3 Transmission housing 4 Soft-iron core 5 Winding (induction coil) 6 Flywheel (2-teeth tooth gap) As you can see in the illustration the inductive sensor with coil and iron core is positioned to sense the teeth of the sensor ring. The frequency of this signal (number of teeth per second) is directly proportional to crankshaft speed. There is a reference point that is determined by removing two teeth. There would be 60 teeth if the two removed to make the reference signal were in place. This makes each tooth and the void next to it 6 degrees in length, each tooth is 3 degrees in length. Sensor Ring Tooth Degree Diagram Page 8.4 Fuel/Ignition Diagnosis & Repair

123 On-Board Diagnostics (OBD II) With the flywheel divided into sixty segments and each segment divided into two 3-degree segments (the high section and the low section), the computer can determine crankshaft movement in less than a degree. Remember the processor is operating with a clock speed of 20 to 30 million cycles per second, so the processor can do a lot of math when the flywheel moves only a portion of a degree. With a six-cylinder engine, the system divides a crankshaft rotation into three 120-degree segments and looks for acceleration in each segment. From this it can determine not only that a cylinder has misfired or not, but identify the cylinder that has misfired. The program that evaluates misfire is complex. It has to be able to distinguish between deceleration caused by rough roads, potholes, shifting, and other non misfire causes, and deceleration caused by misfire. Engine Roughness Detection (Misfire Detection) The DME control unit uses engine roughness detection to detect misfires. For this purpose, a crankshaft revolution is divided into several segments (three segments for 6- cylinder engines and four segments for 8-cylinder engines). The DME control unit compares the times needed for each segment and assigns these to the cylinders. Corresponding deviations are an indication of misfires in the relevant cylinder. The rough-running value of the individual cylinders is then compared with an engine speed- and load-dependent reference value in the DME control unit. When the fuel level is in the reserve range, it flags any misfire that occurs with the information that the misfire occurred when the fuel level was in the reserve range since low fuel levels can result in misfire occurrences from incorrect fuel supply to the engine. In order to determine if crankshaft deceleration is occurring, the misfire monitor must establish a baseline of crankshaft motion (what the crankshaft rotation looks like when there is no combustion). We call this process flywheel adaptation and it has to take place the only time that there is no combustion, during deceleration. In addition to establishing the flywheel adaptation, the misfire program can tell if there is damage to the sensor ring or flywheel. The misfire monitor is unique in that it is the one monitor that will turn on the malfunction indicator light immediately. All of the other monitors have some amount of time that the fault must be present before the light will be turned on. This is due to the damage that can happen to the catalytic converter if misfire occurs in a high RPM/load range or for too long of a period of time. Figure above shows how engine roughness is recognized in order to detect misfires on a 6-cylinder engine (the segments 1, 2, 3 correspond to 20 teeth each on the rotor). Adaptation of Engine Roughness Misfire detection can be used to assign detected misfires to various load and engine speed ranges. A prerequisite for this function is that these load and engine speed ranges have already been adapted. These adaptation values are erased after a reset or after programming the DME control unit. In this case, a basic adaptation must first be carried out during the test drive. This adaptation is carried out in overrun mode (with deceleration fuel cutoff), whereby the mechanical condition of the engine is assessed. All other adaptations are performed automatically depending on load and engine speed while driving. Fuel/Ignition Diagnosis & Repair Page 8.5

124 On-Board Diagnostics (OBD II) Misfire Detection If the engine roughness value of the individual cylinders is significantly higher than the reference value for engine roughness, this is detected and counted as a misfire. Depending on load and engine speed, an error is entered and the Check Engine warning light comes on if the misfiring rate exceeds a certain percentage limit (this function is monitored on 1,000 crankshaft revolutions). Mixture Control Monitor The mixture control monitor utilizes the mixture adaptation system to detect mixture control system malfunctions. When the active mixture control FR (integrator), or the adaptive long-term fuel trim system moves out of a specified range, a fault is detected. If the fault is present for a specified time period and is outside the allowed range for two key cycles, the MIL (malfunction indicator light) is illuminated and a fault is stored. This monitor is part of the mixture control software and is active whenever the engine is running. When a fault is detected, the mixture adaptation system locks and makes no further corrections. The mixture control is already closely monitoring injection time and long term fuel trim, so modifying the software to detect when the fuel trim system has developed a malfunction does not require large changes to the system. hpa Engine load 1/MIN Engine speed % Misfiring rate in percent causing the Check Engine light to come on in the relevant range. Over-revving of the Engine The vehicle analysis log for current vehicles contains the actual values Number of ignitions, range 1 to 6. These actual values can be used to detect how many ignition pulses at an engine speed above the maximum engine speed have taken place in the relevant overspeed range. Range 1: Corresponds to slight over-revving of the engine. Range 2 to 5: The rpm ranges become increasingly higher. Range 6: Overspeed events in the highest range (with subsequent damage) Subsequent damage can even occur from range 4. Further information can be found in the PIWIS information system. The monitors we have discussed so far are continuous monitors that operate all of the time in the background. They run from the time that the engine is started until the vehicle is shut down. These monitors are for the most part software modifications and require little or no additional hardware be added to the vehicle. Now we will examine some of the monitors run once per key cycle. Many of them require additional components. Monitors Run Once Per Key Cycle These monitors are the big difference between OBD-II and earlier systems. They are unique in that they require some special conditions in order to run such as a certain load level, engine RPM, or temperature. Examples: 1. Fuel Tank Ventilation 2. Catalyst Monitor Page 8.6 Fuel/Ignition Diagnosis & Repair

125 On-Board Diagnostics (OBD II) Fuel Tank Ventilation Monitor Tank Venting Tests As the air crosses the carbon in the EVAP canister (a large amount of air at a high flow rate) it picks up the HC s that were deposited in the carbon during the static mode and carries them into the intake where they become part of the fuel used in the combustion process. The fuel mixture control system must adjust the Ti to compensate for the additional fuel that is delivered by this system. The mixture control system operates the purge valve from a map that must be compensated for the amount of fuel that has been stored in the EVAP canister. The amount of HC stored in the EVAP canister can vary greatly. If the vehicle has been operating for an extended period at highway speeds, there will be almost no HCs stored and when the purge valve is opened it is an air leak. 1. Lambda purge flow <> 1: System is functional if fresh air (1a) or HC (1b) detected. 2. Lambda purge flow = 1: Throttle unit actuator will reduce the flow rate through the throttle due to additional flow through the purge valve. The tank ventilation system operates as part of the mixture control system and is even used to compensate for short-term mixture control deviations (if for example an air leak occurs, the mixture control will increase the purge valve on time until the system can adapt). To determine if vapors are flowing through the purge valve (this is the main indicator that the system is functional), the monitor looks at the oxygen sensor. If the sensor moves high or low a sufficient amount when the purge valve is opened, the system is determined to be operating correctly. 1a. Fresh air via EVAP canister. 1b. Fuel vapor via EVAP canister. However, it can be that the valve is operating correctly and the sensor voltage does not move. This would occur when the mixture coming from the system is at the stoichiometric ratio, in this case the oxygen sensor voltage would not move when the purge valve opens. To detect this condition, the monitor also looks at the idle control system when the purge valve is opened, the idle control has to lower the amount of air entering the engine in order to maintain the specified idle RPM, then the system is determined to be operating correctly. This is why this monitor needs idle condition to complete its function. 2. Lambda purge flow = 1: Throttle unit actuator will reduce the flow rate through the throttle due to additional flow through the purge valve. Fuel/Ignition Diagnosis & Repair Page 8.7

126 On-Board Diagnostics (OBD II) Catalyst Monitor So when we see the rear 0 2 sensor with a high voltage signaling, a low 0 2 content, we know the exhaust emissions contain a low amount of CO, HC and NO x, and that the catalytic converter is in good condition. Three-way Catalyst OK (TWC) A: Sensor amplitude ahead of TWC B: Sensor amplitude after TWC The goal of the catalyst monitor is to find out if the catalyst is doing its job of lowering the N0x, HC, and CO emissions in the exhaust flow. To do this, we install a second 0 2 sensor after the catalyst (or in the case of a system with two catalysts per bank after the first catalyst). If the catalyst is operating correctly, the O 2 level at the second sensor will be relatively low. If the second sensor looks just like the first (mixture control) sensor, then the catalyst is not doing it s job and is defective and needs to be replaced. We can see in the two examples above, when the catalyst is operating correctly, the 0 2 sensor in front moves in a range between 100mV and 900mV, and the sensor behind the catalyst, in a range between 800mV and 900mV (this can be broader but will be above 500mV). The voltage is high and that means 0 2 is low. This is due to the fact that when the catalyst is operating correctly, it uses up the 0 2, turning the CO and HC into C0 2 and H 2 O. It not only needs the 0 2 in the exhaust stream, it also uses up the 0 2 from catalyzing the NO x and reducing it to free 0 2 and N. Three-way Catalyst not OK (TWC) A: Sensor amplitude ahead of TWC B: Sensor amplitude after TWC X: Delay due to gas running time If we see that the rear sensor is the same as the front sensor, we know the catalyst is not operating and the tailpipe emissions will be above the legal limit. The reason that this monitor is run only once per key cycle and has special conditions, is that if we don t run it when the catalyst has had a chance to get up to operating temperature and has a good amount of flow, we can fail a good catalyst. To understand the way the engine management computer looks at inputs, we need to remember that it has no eyes, so it cannot look at the waveforms of the two sensors and compare them as we do. The processor can only deal with numbers it is just an adding machine a complex fast adding machine but still just an adding machine. Notes: Page 8.8 Fuel/Ignition Diagnosis & Repair

127 On-Board Diagnostics (OBD II) General Notes: The comprehensive component monitor checks all of the circuits and electric components of the systems. It will store a fault if there is a malfunction detected in the components, or circuits, whenever the system is operating. If the dynamic monitor detects a malfunction, the MIL will be illuminated when the conditions for confirming that fault are met. An appropriate fault will be stored in memory. This occurs only when the monitor is running. The diagnostic monitors run when the conditions for operation are met. This is not necessarily every time the vehicle is operated. The required conditions for diagnosis can be different for the varied systems, and can include engine temperature, load, RPM, time, and other variables. For example; the pressure sensor tank leak test and LDP tank test must be run when the engine is running, while the DM-TL leak test can be run without the engine running, or even with the key off. So when we repair a defect in the tank, or connected lines and components, it is important to perform a short test. If we do not this, the system may not run the diagnosis for a period of time. When it does, the MIL will turn back on if the vehicle is not repaired. When we look back over the section on OBD-II, we can see that if there is a malfunction in the engine management system, the diagnostic system will find it most of the time. Occasionally, we will have a situation where a sensor will be out of range far enough to cause a performance problem, but not far enough to set a fault. The one problem for the technician with OBD-II is when we don t fix the problem, the MIL comes back on. When we repair a MIL lamp on a engine management system malfunction, we must make sure the monitors involved are run when we test drive the vehicle. All P0xxx codes are standardized codes. However each manufacturer can use other DTCs in addition to the standardized codes. This applies when the manufacturer integrated additional functions in the control module that can be diagnosed and that exceed the law. These codes are identified as P1xxx, for example: P1100 The first digit of the code (letter) identifies the system the code has set. There are 4 systems: B For Body C For Drive Train P For Engine U For Future System For OBD II only the P code is required. The second digit identifies the generic code (P0xxx), or the manufacturer code (P1xxx). The third digit identifies the major subassembly where a malfunction occurred. They are: P01xx Fuel P02xx Air Ratio P03xx Ignition System P04xx Additional Emission Controls P05xx Vehicle Speed and Idle Speed Control P06xx Control Module and Initiating Signals P07xx Transmission P-Codes Standardized Trouble Codes SAE J DTC-Diagnostic Trouble Codes Diagnostic Trouble Codes that are monitored by the engine control module are standardized, which means that all manufacturers must use the same Diagnostic Trouble Codes. The Diagnostic Trouble Codes (DTC) ia always a 5-digit alphanumeric value, example: P0100 Fuel/Ignition Diagnosis & Repair Page 8.9

128 On-Board Diagnostics (OBD II) Page 8.10 Fuel/Ignition Diagnosis & Repair

129 Additional DME Functions & Special Control Systems Subject Page Variable Camshaft Control Variable Oil Pump Fan Control Variable Deceleration Fuel Cutoff Knock Control Turbocharging VTG Turbocharger Principle of Torque Flow Calculation of Required Values Thermal Management Panamera & Cayenne V Thermal Management Sports Cars 9x Overview Shut-off Valves Engine Coolant Shut-off Valve Thermal Management For Heat Exchanger Thermal Management For Transmission Map-controlled Thermostat Engine Coolant Temperature Sensor Radiator Outlet Coolant Temperature Sensor Operating Conditions Electric Fans Auto Start Stop Coasting Function Vehicle Electrical System Recuperation Sport Button Systems That Effect Management System Operation Via Data Transfer Fuel/Ignition Diagnosis & Repair Page 9.1

130 Additional DME Functions & Special Control Systems General lower residual gas amount at idle speed and a higher charge at high revs. At low or medium revs or in specific partial load ranges, adjusting the intake camshafts towards early Intake opens/closes results in a higher maximum charge. At the same time, it increases the residual gas amount in the partial load range and influences fuel consumption and exhaust emissions accordingly. Cam Timing Control This section of the training course covers other engine control functions, functions and special control systems which may or may not have a direct impact on fuel and ignition control, however these systems work with or with in the DME control unit. In addition, there are systems that send data and requests for intervention to the engine management system, and, receive data from and operate in synchronization with the engine management system In 1992 with the VarioCam equipped 968, Porsche began to use digital electronic control of camshaft timing. In 1997 the Boxster (986) was equipped with VarioCam and all subsequent Porsche power plants have incorporated digital electronic cam timing control. Many have valve lift control as well. Until 2002 and the advent of VarioCam Plus on the naturally aspirated 911 Carrera (996) all of the cam adjustment systems made the cam timing change in one step so they were either off or on all of the timing change or none. Variable Camshaft Control For valve timing, it is important that the behaviour of the gas columns flowing in and out of the cylinder changes significantly as a function of the engine speed or throttle valve opening for example. In the case of fixed valve timing, the gas cycle can only be adapted in the best possible way for a specific operating range. Variable valve timing and valve lift enables adaptation to various engine speeds and cylinder charges. Camshaft control is activated by the Motronic control This has the following advantages: More power Improved torque curve over a wide rev range Reduced pollutant emissions ower fuel consumption Reduced engine noise Changing the angle of the intake camshafts changes the valve timing for Intake open and Intake close. If the intake camshafts are adjusted to a late Intake opens/ closes at idle speed or at high revs, this will result in a Page 9.2 Fuel/Ignition Diagnosis & Repair The operational principal of the one step VarioCam is illustrated in the graphic. We see the non actuated position in black (this is how a non VarioCam 944 operates all of the time). The exhaust camshaft is chain driven off of the crankshaft and the intake camshaft is chain driven off of the exhaust camshaft. If we push the guide block down (the position shown in red), we advance the intake cam without moving the exhaust cam. The 968 intake cam is moved by 15 degrees, the Boxster intake cam is moved by 25 degrees.

131 Control is via a solenoid hydraulic valve to advance the cam.the DME grounds the solenoid and oil pressure moves the piston attached to the lower chain guide to the advanced position. The upper chain guide is attached to the tensioner that acts against the slack side of the chain. Additional DME Functions & Special Control Systems The initial actuation is at approximately 1500 RPM, at higher RPM (approximately 5500), the cam timing is returned to the base position, since at higher RPM the advanced cam timing would interfer with resonant intake charging and reduce performance. The operations of the actuator and control solenoid hydraulic circuit are described in the following illustrations. Figure 3 Figure 4 High Torque Setting Figure 1 Figure 2 Figure 3 - Solenoid (1) is actuated by the DME control unit, engine oil pressure forces both chain guides (2) and (3) down. This corresponds to the high torque setting in the middle RPM range. Figure 4 - Solenoid (1) is energized and forces control piston (12) down. Oil pressure (red) fills and tensions the tensioner. Oil pressure (light red) now also enters the large annular chamber (13) and forces the complete actuator with piston (11) down, overcoming the force of the spring (10) at the same time. Non-pressurized excess oil (blue) is diverted. Basic Setting Figure 1 - Adjustment of the chain tensioner is performed by hydraulic pressure cylinders and spring packs. Switchover pulses to the solenoid (1) are produced by the DME control units. When deenergized, both chain guides 2 and 3 are at raised position. Figure 2 - Solenoid (1) deenergized. Oil pressure (red) fills interior of chain tensioner (2) and supports force of springs (3) and (4). Both tensioner chain guides (5) and (6) rest on the roller chain links (7) and (8). Oil pressure (light red) is also fed into the annular chamber (9) and supports the spring (10). Piston (11) remains at top. Non-pressurized oil (blue) is diverted. The systems in the 968 and Boxster are similar in operation, the only added sensor is an oil temperature sensor, which is required so the actuation RPM can be raised when oil temperature raises to the point that oil pressure drops off. This form of cam timing control is easy for DME, all that is needed is a pin on the control unit that can be held to ground, an oil temperature sensor, and the software to control when to energize the actuator. In 2001, the 911 Turbo (996) was equipped with VarioCam Plus. This system also moves the cam timing in one step, however, it utilized a sliding helical gear adjuster for the exhaust and intake cams which were driven by the same chain. Fuel/Ignition Diagnosis & Repair Page 9.3

132 Additional DME Functions & Special Control Systems Electronic control for the valve lift function is very similar to cam timing control. All the DME needs to do is switch a pin to ground when the software determines that the conditions for large valve lift have been met. Piston position - retarded, minor valve overlap. VarioCam Plus shown in idle speed range inner tappet controls valve stroke (3 mm valve lift) and camshaft adjuster unit is in retard position (minor overlap). Piston position - advanced, major valve overlap. With VarioCam Plus, once the adjuster is adjusted to the advanced position, it remains at the advanced position until engine speed drops below actuation RPM. In addition to advancing intake cam timing, VarioCam Plus changes the valve lift from 3 mm to 10 mm on the 911 Turbo and 3 mm to 11 mm on the 911 Carrera (996). The actuation RPM for both functions is load dependant. The valve lift is changed by having two cam profiles and hydraulically locking the lifter in order to increase the valve lift. VarioCam Plus shown in upper full-load range tappet is interlocked (10 mm valve lift) and camshaft adjuster unit is in advance position for peak torque and power. In 2002, the naturally aspirated 911 Carrera (996) was equipped with VarioCam Plus, this version of VarioCam Plus included infinitely adjustable cam timing (vane cell adjuster). As in all of the previously utilized cam timing adjustment systems, the exhaust cam remains fixed and the intake cam is moved. The difference is the intake cam can be moved to any position in its adjustment range. This is achieved by cycling the solenoid hydraulic valve between its three positions advance, retard and hold. Page 9.4 Fuel/Ignition Diagnosis & Repair

133 Additional DME Functions & Special Control Systems Camshaft Vane Adjuster - Front View Cutout Solenoid Valve Operation P = Oil pressure in T = Oil return B = Retard cells A = Advance cells Camshaft Vane Adjuster - Side View Cutout Notes: Fuel/Ignition Diagnosis & Repair Page 9.5

134 Additional DME Functions & Special Control Systems Non-return Valve Operation The VarioCam system decides where it needs the intake cam to be positioned, and operates the hydraulic solenoid valve to put it there. With the PIWIS Tester we can see both the actual cam position and the position determined by the camshaft timing control system. The 911 Carrera (996) also utilizes valve lift control. In 2003, the Boxster (986) and Cayenne V8 were equipped with vane cell adjusters, however no valve lift control. 1 - Direction of Adjustment - Retard 2 - Direction of Adjustment - Advance 3 - Camshaft Adjuster 4-4-way Solenoid Valve 5 - Non-return Valve 6 - Oil Pump 7 - Oil Sump In 2005 with the introduction of the Cayenne V6 both camshafts were equipped with vane cell adjusters. The V6 motor also has a double Hall sensor system on each camshaft. The advantage of having a vane cell adjuster on the exhaust cam is for the main part to control NOx emissions. 911 VarioCam Plus This new system uses the same cam position sensors as the Turbo (996); they sense cam position four times per cam revolution and with one sensor per bank, this doubles to eight times per cam revolution and four per crankshaft revolution. This allows the cam timing control system to very accurately determine camshaft position. In addition, these signals are utilized for the fast start system. The DME stores the stop position of the engine so that the DME can begin to immediately actuate injectors and ignition without waiting to see the cam position. 1 - Vane cell adjuster, intake camshaft 2 - Vane cell adjuster, exhaust camshaft 3 - Timing case 4 - Valve for variable camshaft control, intake 5 - Valve for variable camshaft control, exhaust 6 - Oil channels to annular groove of camshafts As we can see, cam timing control is simple, electronically speaking. On the most complex system, the Carrera (996), there are two one position solenoids, and two pulse-width-modulated solenoids controlled via software. Both utilize a programmed map using engine speed, load, and engine temperature to index cam position. The mechanical components are more complex, but the payoff in torque and horsepower are worth the effort. Signal from camshaft position sensors (Hall sensor) Page 9.6 Fuel/Ignition Diagnosis & Repair

135 Additional DME Functions & Special Control Systems Variable Oil Pump on V8 Engines The DME control unit is responsible for the demandcontrolled operation of the variable oil pump, while adjustment is performed hydraulically. Discharge of excess pressure oil is not necessary. In addition, the variable oil pump offers the possibility of specifically lowering the oil pressure to the actual engine requirement in the lower speed range. This results in a further saving potential with regard to the drive power of the pump (green area). The DME control unit uses the engine speed, temperature and torque request as input values. Based on this information, the engaged gear wheel width and thus the geometric displacement volume of the gear wheel set is changed through the axial movement of a gear wheel (this is moved hydraulically) and this in turn changes the oil pressure. In the case of conventional oil pumps, the volume flow rate increases practically linearly as a function of the engine speed. The oil quantity which is not needed by the engine is discharged through a bypass valve in the pump. As a result, a large amount of the pump work already performed is lost at high speeds in particular (green area). The pump ensures that only the pumping work required for the relevant load range of the engine is performed. This reduces the energy consumption of the oil pump to a minimum and also ensures demand-controlled lubrication. 1 Drive wheel 2 Fixed gear wheel 3 Axially displaceable gear wheel 4 Control valve A de-energized B fully energized Notes: Fuel/Ignition Diagnosis & Repair Page 9.7

136 Additional DME Functions & Special Control Systems Fan Control Boxster (987) and 911 Carrera (997) Fan Control Chart In the earlier models (986/996), the radiator fan was activated in two stages using relays. A resistor was preswitched in the first stage. The 996 Turbo had a threestage activation system in which only the third stage was operated without a resistor. The newer systems mainly have continuous activation of the radiator fans (used for the first time in the Cayenne from MY 2003 onwards). Example: Continuous Fan Control of the Electric Fans (997/987) Control of Electric Radiator Fans With stepped control, when a temperature threshold was exceeded the next fan speed had to cover the entire allocated temperature range. With continuous control, the fan speed can be continuously adjusted to the actual requirement. This means that the fan speeds can often be reduced, thereby reducing noise and vibrations and requiring less current and therefore creates less of a load on the vehicle electrical system. With the 911 Carrera (997) and Boxster (987), continuous fan control for the radiators is introduced for sports cars. This new feature permits continuous control of the fan speed as a function of the coolant temperature and the system pressure in the air conditioning system, instead of two-stage control. The air throughput required is calculated by the Motronic control unit, which transmits the information to the gateway control unit via CAN. The gateway control unit then sends the signal to the front-end control unit. The front-end control unit activates the radiator fan control unit using a pulse-width modulated (PWM) activation signal, which activates the left and right radiator fans correspondingly via the power output. Page 9.8 Fuel/Ignition Diagnosis & Repair

137 Additional DME Functions & Special Control Systems Example of Two-stage Engine Compartment Blower (997) The engine-compartment blower on the engine compartment lid of the first 911 Carrera (997) was activated in two stages. Stage 1 (continuous operation) is activated by the fuel pump relay and using a changeover relay and switch-off relay. After the fuel pump relay, a resistance line (which limits the power to approx. 10 watts) goes to the enginecompartment blower via the switch-off relay. In stage 2, the engine-compartment blower is activated directly (power of approx. 33 watts) by the DME control unit via the changeover relay and switchoff relay as a function of the coolant temperature, the engine compartment temperature and a ratio between the intake and ambient temperature. Stage 2 is also activated for sporty acceleration, which is detected in the DME control unit. If the temperature is less than the relevant temperature parameters, the system switches back to stage 1. If the engine compartment lid is opened while the enginecompartment blower is active, the switch-off relay switches off the engine-compartment blower. The engine compartment temperature is monitored for approx. 30 minutes after the engine is switched off. During this time, the engine-compartment blower can continue running or switch itself on again. If there is no measurable drop in temperature after 5 minutes when stage 2 is activated, the temperature warning light on the coolant temperature display in the instrument cluster will start flashing. The warning Eng. comp. fan failure will also appear on the on-board computer. Variable Deceleration Fuel Cutoff Variable deceleration fuel cutoff is an enhancement of conventional deceleration fuel cutoff on the Panamera and Cayenne from MY 2011 onwards and 9x1 models. This essentially involves controlled interruption of the fuel supply in driving situations where the combustion engine is not required to output any power but is kept moving by the inertia mass of the vehicle (overrun, e.g. when driving downhill). The objective is to drive as long as possible in overrun mode with deceleration fuel cutoff. Compared with the usual deceleration fuel cutoff systems, in which fuel injection is resumed as from a fixed engine speed, variable deceleration fuel cutoff systems resume fuel injection flexibly depending on the driving situation, which may correspond to an even lower engine speed. This results in greater fuel economy. Main features: Controlled interruption of fuel supply in overrun mode, e.g. when driving downhill. After a phase with deceleration fuel cutoff, fuel injection is resumed variably depending on the driving situation, which may correspond to an even lower engine speed. The relevant input variables for controlling variable deceleration fuel cutoff are: engine temperature, engine speed, engine speed gradient (change in rpm), as well as transmission fluid temperature and transmission gear. Deceleration fuel cutoff is maintained even in the overrun coasting phase with downshifts. Deceleration fuel cutoff mode is ended only in the event of significant deceleration (see stability management EDC). The resumption speed after deceleration fuel cutoff is 850 rpm to 950 rpm. Notes: Fuel/Ignition Diagnosis & Repair Page 9.9

138 Additional DME Functions & Special Control Systems Knock Control General The term knocking combustion or knocking refers to an uncontrolled, explosive combustion process in the engine s combustion chamber. Knocking combustion is considerably faster than normal, required combustion. The flame speeds of normal combustion are approx m/sec., while the flame speeds of knocking combustion are approx m/sec. High peak pressures and pressure fluctuations therefore occur in the high frequency range. This results in strong mechanical loads on the engine. The cylinder head, spark plugs, valves and pistons are particularly at risk. Causes of Uncontrolled Fuel Combustion Uncontrolled, explosive combustion processes are caused by spontaneous ignition of the mixture ahead of the actual flame front that was started by specific ignition of the mixture by the spark plug. Spontaneous ignition of the as yet uncombusted mixture is caused by the increases in pressure that occur in addition to piston compression and the resultant increases in temperature as a result of the expansion of the parts of the mixture that have already ignited. High air and engine temperatures, fuel with insufficient knock resistance, or mechanical deposits in the combustion chamber increase the likelihood of spontaneous ignition. The objective of knock control is to determine the change in the timing angle for each individual cylinder as a result of detected knocking. This includes both the actual calculation of the required retardation compared with the normal ignition system and storing the calculated values in an adaptation map. Later ignition moves the start of combustion further into the engine s expansion stroke. This prevents the critical point for spontaneous ignition from being exceeded in areas with uncombusted mixture. Knock control is only active at an engine temperature of over 104 F. (40 C.) and above idle speed. Retardation of the Timing Angle When knocking is detected, the timing angle of the corresponding cylinder is retarded by a crank angle of 3 per knock event. This cylinder-specific ignition timing control is added up in the DME control unit as a function of load and engine speed. For engine roughness reasons and to prevent misfire detection, retardation for every calculation is limited to a band range around the mean value of the last retardation that was output. The band range depends on the engine speed. Retardation is also limited to a crank angle of about 12 and 0. If the engine is no longer operating in a range in which knock control is active, the last retardations remain stored until the engine starts operating in the active area again. A crank angle of 0 is output to the ignition as the control value in the engine s non-active range. The retardations are set to 0 when the engine is switched off. Advancement of the Timing Angle The retardations following the knock event are reversed for each individual cylinder when the cylinder-specific advancement time has elapsed. This time is reset for each detected knock event. If no knocking occurs after the advancement time has elapsed, the retardation assigned to the corresponding cylinder is reduced by one step. The timer is restarted. Load Dynamics Load-dynamic engine operation can result in an increased tendency to knock and a faster increase in engine noise depending on the current engine temperature. Since the higher engine noises make knock detection more difficult, but the increasing tendency to knock still has to be countered, an additional ignition timing retardation (dynamic threshold) is introduced as mentioned earlier. Engine Speed Dynamics In contrast to load dynamics, only changes to the noise level are mainly critical for knock control with engine speed dynamics. The triggering of engine speed dynamics and the triggering of load dynamics depend on the engine temperature. Page 9.10 Fuel/Ignition Diagnosis & Repair

139 Additional DME Functions & Special Control Systems Knock Sensors Design of a Knock Sensor The current V8 engines have four knock sensors, which are installed in the V of the engine block. The 6-cylinder engines each have one knock sensor per cylinder bank. The knock sensors required for detecting uncontrolled combustion processes are screwed directly to the engine block and detect the structure-borne sound vibrations triggered by combustion. The knock sensor converts these into electrical signals and sends them to the DME control unit. This assigns the knocking to the corresponding cylinder and retards ignition timing for this cylinder. 1 Piezo-ceramic element 2 Seismic mass with pressure forces F 3 Housing 4 Screw (Observe tightening torque!) 5 Contacts 6 Electric connection 7 Engine block V Vibration Notes: Fuel/Ignition Diagnosis & Repair Page 9.11

140 Additional DME Functions & Special Control Systems Knock Sensor Signal Knock Resistance The octane rating indicates the knock resistance of a fuel. The higher the octane rating, the greater the resistance to engine knock. Two different procedures are used internationally to determine the octane rating: The Research Method (RON) and the Motor Method (MON). RON (Research Octane Number) is the number determined using the Research Method. It can be regarded as the essential index of acceleration knock. The top half of the illustration shows the signals without knocking, the lower half shows the signals with knocking. 1 Pressure curve in the cylinder 2 Filtered pressure signal 3 Signal from the knock sensor to the DME control unit Failure of Knock Sensors If a knock sensor fails, the ignition timing angles of the affected cylinder group are retarded. This means that a safety ignition timing angle is set to late. Knock control for the cylinder group of the remaining, intact knock sensors is unaffected. If all knock sensors fail, the DME control unit goes into knock-control emergency operation during which the ignition timing angles are generally retarded, thereby reducing engine power considerably and increasing fuel consumption. Notes on Fuel Quality The Owner's Manuals supplied with all vehicles define the fuel types and quality to be used. Further information can be found in the PIWIS information system. MON (Motor Octane Number) is the number determined using the Motor Method. It basically provides an indication of the tendency to knock at high speeds. The Porsche gasoline engines are designed to provide optimum performance and fuel consumption if unleaded premium fuel with 98 RON/88 MON is used. If unleaded fuel with a lower octane rating is used, the engine s knock control system adapts the ignition timing. If fuels are used that do not conform to the defined specifications, the vehicles will not quite achieve the specified performance and fuel consumption can also increase slightly. Maintenance schedules, fuel filters, etc. are also tailored to the fuel specifications. E10 Fuels In addition to the details in the Owner s Manual, a description of the compatibility of E10 fuels for Porsche vehicles can also be found under Information Media/Manufacturer's Certificates in the PIWIS information system. Fuels That Do Not Meet The Requirements In some markets, the quality of the fuel available may not meet Porsche requirements and can result in coking, deposits in the combustion chamber and oil sludge formation. In this case, an additive recommended by Porsche can be added to the fuel as described in the Owners Manual and in the PIWIS information system. Always read and comply with the instructions and mixing ratios specified on the container. Page 9.12 Fuel/Ignition Diagnosis & Repair

141 Additional DME Functions & Special Control Systems Idle Speed control Through Ignition Timing Control and Electronic Throttle Idle speed control must strike a balance between the engine torque output and the engine load, thereby ensuring a constant engine speed. The engine load at idle speed comprises various load torques - the friction torque produced in the engine from the crank and valve drive and the auxiliary units (e.g. the coolant pump). These internal friction torques, which are balanced by idle speed control, change slowly during the service life of the engine. They are also extremely temperature-dependent. In addition to these internal friction torques, there is also the external load created by the operating loads, such as air conditioning, etc. Control Interventions Idle speed control can physically intervene as follows: Air control Tried-and-tested intervention in the current systems via electronic throttle. If a well run-in engine requires less air at idle speed than is produced by the throttle valve and idle-speed adjuster, the electronic throttle will be closed slightly. Timing angle control The option that works considerably faster is intervention in the timing angle. Using a speed-dependent timing angle, it is possible to advance the timing angle and increase engine torque as the engine speed falls. Idle speed fluctuations can be balanced using this fast path. These external loads fluctuate significantly because units are switched on and off again. Modern engines, in particular, like those used for a long time now at Porsche, with low inertia masses and large-capacity intake systems are sensitive to these load changes. Notes: Fuel/Ignition Diagnosis & Repair Page 9.13

142 Additional DME Functions & Special Control Systems Turbocharging An increase in power as a result of increasing displacement or a higher engine speed is limited by the physical size and inertia forces, which increase extremely quickly at high engine speeds. Turbocharging compresses the air flow upstream, which means that it supplies air at pressures above atmospheric pressure. This allows greater cylinder charging, resulting in a higher torque. Turbocharging is normally performed using a turbocharger or a compressor. The turbocharger uses the exhaust gas flow to drive the turbine wheel, which is connected to the compressor wheel, whereas a compressor is driven mechanically by the crankshaft using a belt drive. Turbocharger Of the known methods of turbocharging combustion engines, exhaust-gas turbocharging is the most widely used. This enables high torque and high performance combined with good engine efficiency to be achieved even on engines with a small displacement. On the air side, the flow ratios are reversed in the compressor, which is also turning. The fresh air enters the centre of the compressor axially and is driven out radially by the blades and is thereby compressed. The turbocharger is located in the hot exhaust tract. It must therefore be made of very high-temperature resistant materials. Turbine Design Different types of exhaust-gas turbines are used depending on the vehicle. The mixed-flow and radial turbines have a different exhaust-gas impact angle. Compared with the radial turbine, the mixed-flow turbine offers slight advantages in terms of weight, installation space and inertia of the rotating parts. In contrast, however, the radial turbine offers improved efficiency and therefore generates a lower exhaust gas backpressure. The resultant advantages for the combustion process are specifically exploited in order to reduce fuel consumption. The main components in the exhaust-gas turbocharger are an exhaust turbine and a compressor whose wheels are arranged on a common shaft. The exhaust turbine and compressor wheels can reach speeds of up to approx. 160,000 rpm at full throttle. The energy for driving the exhaust turbine is mainly taken from the exhaust gas; the energy used here is the energy contained in the hot, pressurized exhaust gas. Energy must also be expended, however, to further accumulate the exhaust gas when it leaves the engine and therefore obtain the necessary compressor performance. This illustration shows the Cayenne Turbo with wastegate turbocharger. A Exhaust gas flow to the turbine wheel MFT Mixed-flow turbine (Cayenne Turbo up to MY 2006) RFT Radial flow turbine (Cayenne Turbo DFI) The hot exhaust gas blows onto the exhaust turbine radially and moves it in a fast rotational movement. The inward-facing turbine wheel blades route the exhaust gas to the center, where it then emerges again axially. Page 9.14 Fuel/Ignition Diagnosis & Repair

143 Additional DME Functions & Special Control Systems Turbocharger Control Porsche has utilized exhaust gas turbocharging to improve the performance of power plants since the 1970s. In the 1980s we began to control the turbocharger with electronic control systems. To understand how electronic control of turbocharger works, we need to examine how a basic waste gate control system works. Compressor Section Turbine Section Basic Turbocharger System 1 - Combustion Chamber 2 - Turbocharger 3 - Wastegate 4 - Air Intake 5 - Exhaust The turbocharger at #2 is basically a supercharger, other variations of superchargers require some type of mechanical drive system to pump air into the engine. A turbocharger utilizes a turbine in the exhaust flow to drive the impeller in the intake to pump air into the engine combustion chamber #1. The impeller is on one end of the drive shaft in the compressor housing and the turbine is on the other end in the turbine housing. The shaft has oil pressure lubricated bearings in the center section. In water cooled Porsche models, the bearing section has a water cooled section between the bearings and the turbine housing to keep the heat from the exhaust from heating the oil in the bearings and passages to the point that they become blocked by burnt oil (coking). 1 - Compressor Housing 2 - Compressor Wheel 3 - Axial Bearing 4 - Compressor Back Wall 5 - Turbine Housing 6 - Bearing Housing 7 - Rotor 8 - Sleeve B - Oil Pressure From Engine D - Oil Return Flow F - Water Jacket The speed of the turbine and impeller is not controlled by engine speed, but is a function of the balance between the energy that compressing the air charge requires, and the energy that the exhaust gas puts into the turbine. The speed of the rotating assembly can be very high, speeds up to 100,000 RPM are not uncommon. Fuel/Ignition Diagnosis & Repair Page 9.15

144 Additional DME Functions & Special Control Systems If the turbocharger did not have a control system, the volume of air the compressor pumps and the amount of pressure in the intake would rise to a level that would damage the engine. To control the volume and resulting pressure generated by the turbocharger, we use a waste gate (#3 in Basic Turbo Charger System illustration). A waste gate is a pressure-controlled bypass around the turbocharger for the exhaust gas. The turbocharger is a restriction to the exhaust gas flow, so when the gas flow is given a path around this restriction it chooses the path of least resistance, the amount of exhaust gas passing through the turbocharger is lowered thereby lowering the volume of air pumped into the engine. The waste gate which is a valve connected to a pressurecell controls the size of the bypass. The pressure cell acts against a spring that holds the valve closed. The pressure cell is connected to the intake manifold by a pressure line, when intake pressure rises to a level that overcomes the spring, the pressure begins to open the valve. As pressure rises higher, the bypass opens further until the balance point of the system is reached and the pressure stabilizes at the maximum allowed by the waste gate. We can see this pressure curve in the Pressure/RPM graph marked as A. Pressure/RPM Curve This is how a waste-gate without electronic control works. The boost rises steeply as RPM rises until it reaches it s maximum level and then flattens out. Notes: Page 9.16 Fuel/Ignition Diagnosis & Repair

145 Additional DME Functions & Special Control Systems Electronic Turbocharger Control Porsche first used digital electronic turbocharger control in 1986 on the 944 Turbo, most of the turbocharged Porsche motors since have had digital electronic turbocharger control. With digital electronic turbocharger control the basic system operates like our previously described wastegate system. The difference is there is an electronic solenoid valve #1 that can vent the pressure that acts on the wastegate pressure cell to atmosphere (at the compressor stage inlet). When this happens, the turbocharger will not be controlled by the wastegate since the pressure that would open the bypass is vented or partially vented to atmosphere. Turbo charger control needs to know what the pressure in the intake manifold is in order to control the wastegate, for this reason there is a pressure sensor connected to the intake manifold. With digital control of the turbocharger, we have mapped control of the wastegate. Later systems have adaptive control, the vehicle specific sections have details of the control strategies for the turbo charger. For the most part, cycling the wastegate control is the main function that engine management has to provide for turbocharger control. Other functions that can be provided, include control of electric coolant pump and the boost recirculation control. The air volume and pressure produced by the turbocharger will now rise above the non electronic wastegate control curve. We see this new control curve in the Pressure/RPM graph as B, the shaded area is the additional pressure electronic control provides. At C is the safety curve where the fuel injectors would be shut off to avoid damage to the engine from excessive boost. Fuel/Ignition Diagnosis & Repair Page 9.17

146 Additional DME Functions & Special Control Systems Boost Pressure Control In the wastegate turbocharger, the DME controls the boost pressure via the wastegate valve (via adjustable guide blades on the VTG turbocharger). The pressure for opening the wastegate valve is modulated by activating the cycle valve using a corresponding pulse/duty factor. Wastegate Turbocharger In turbochargers with a wastegate valve, the exhaust gas is routed past the turbine directly to the exhaust when the required boost pressure is reached, which prevents the turbine speed from increasing further. The basic boost pressure (without control) is < 20.3 PSI (1,400 mbar) absolute pressure. The pulse/duty factor of the cycle valve (0 to 95 %) as well as the boost pressure and the boost pressure adaptation of ranges 0 to 4 can be read out from the Actual values using the PIWIS Tester. Graph below: On some vehicles, additional power is made available by increasing the boost pressure when the Sport button is pressed (yellow line). The boost pressure is reduced in the event of problems (emergency operation - blue line). 1 Flange to the exhaust manifold 2 Exhaust turbine 3 Wastegate valve 4 Pressure unit for boost pressure control through the bypass valve (wastegate) rpm Engine speed in rpm mbar Boost pressure (in millibar absolute pressure) blue Basic boost pressure in emergency mode purple Boost pressure in normal mode yellow Boost pressure with Sport button activated 1 Cycle valve for boost pressure control 2 Pressure side (boost pressure from right-hand turbocharger) 3 Vacuum (from intake side of left-hand turbocharger) 4 Controlled control pressure to the boost-pressure control valves 5 Pressure unit at the turbochargers for opening the wastegate valves The boost pressure is controlled through electrical activation of the cycle valve for boost pressure control (1) by the DME control unit. This modulates a corresponding control pressure (4) onto the pressure unit of the wastegate valve (5). Page 9.18 Fuel/Ignition Diagnosis & Repair

147 Additional DME Functions & Special Control Systems This picture shows a water-cooled turbocharger for the right-hand cylinder bank on the Cayenne Turbo with the pressure unit for boost pressure control as well as the lubricating oil supply and suction lines. Acceleration with boost pressure Decerlation Air Control If acceleration is interrupted, the compressed air accumulates ahead of the closed throttle valve and causes the turbine wheels to slow down significantly. During acceleration, therefore, the turbocharger must first build up speed again in order to reach the required boost pressure. Overrun air control opens a bypass between the intake and delivery sides of the turbocharger during the overrun phase. This allows the turbine wheels to run freely, particularly in the event of sudden load changes. The air is controlled by vacuum. On most vehicles, the overrun air control system is located outside of the turbocharger between the intake and pressure sides. It is integrated in the turbocharger on the first 997 Turbo with a VTG turbocharger. Example of the Cayenne Turbo The electric switching valve for overrun air controls the diverter valve via the control line (7). Pressure closes the valve, while vacuum opens it. In MY 2003 vehicles, the electric switching valve is installed at the rear left intake manifold, while it is under the intake manifold from MY 2008 onwards. Overrun mode with overrun air 1 Intake side (from air cleaner to turbocharger) 2 Pressure unit for boost pressure control 3 Turbocharger 4 Diverter valve (between intake side and pressure side) 5 Pressure side (from turbocharger via the charge-air cooler to the electronic throttle) 6 Merging of compressed air from the left and right (ahead of electronic throttle) 7 Control line to diverter valve Notes: Fuel/Ignition Diagnosis & Repair Page 9.19

148 Additional DME Functions & Special Control Systems VTG Turbocharger The 911 Turbo (997) uses two turbochargers with variable turbine geometry (VTG). This design combines the advantages of a small and a large turbocharger in one and enables optimum use of the exhaust energy for turbocharging, whatever speed the engine is running at. Furthermore, wastegate valves are no longer needed. At the heart of the variable turbine geometry construction are the adjustable guide blades that specifically direct the exhaust flow from the engine onto the turbine of the turbocharger in a variable manner. Boost pressure is built up by closing the guide blades and limited by opening the guide blades. Variable turbine geometry thus permits both very good responsiveness with high torque values even at low engine speeds and high output values at high engine speeds. The high torque is available for a significantly wider engine speed range. Guide blades open, boost pressure is reduced. 1 Servo motor 2 Control unit with potentiometer 3 Connecting link 4 Adjusting ring 5 Guide blades 6 Exhaust gas temperature sensor Guide blades closed, boost pressure is built up. When carrying out maintenance work on engines with VTG turbochargers, the adjustment mechanism of the VTG turbocharger must be checked for smooth operation as per the PIWIS information system and the ball joints must be greased using a special lubricant. Notes: Page 9.20 Fuel/Ignition Diagnosis & Repair

149 Additional DME Functions & Special Control Systems Principle of Torque Flow (revisited) On vehicles with an electronic throttle, the basic concept of torque flow is based on the coordination of the various requests on a physical level. The driver s torque request is determined by the accelerator-pedal position and the engine speed. Additional functions, such as idle speed control, anti-slip regulation (ASR), air conditioning, etc., must also transmit their torque needs to the control unit (see figure below). Protective functions, such as electronic engine and vehicle speed limitation, can also limit the permissible engine torque. The engine torque output must enable the desired driving state and the operation of all units and components and must meet the external requests from the drivetrain and driving dynamics systems. The maps and characteristics are only engine dependent through this interface. Furthermore, there is no cross-coupling of individual assemblies. This makes engine tuning considerably easier. Torque control was introduced with the first DME control units ME 7.X (with electronic throttle) in the 911 Carrera 4 (996). Prior to this, interventions in engine control were defined and implemented independently of each other based on the available control variables, such as cylinder charge, timing angle and fuel mass. The purpose of torque flow is to select suitable engine control variables in order to adjust the internal torque so that all losses are covered and the engine torque is sufficient to meet the driver s request. The basic variable for the torque structure is the internal torque from combustion. This is the torque that is produced by the gas pressure in the high-pressure phase. If the friction and losses of the gas cycle are subtracted from this torque, the result is the engine torque. For the torque coordinator of the DME, there are two possible control paths for adjusting the internal torque. One of these is a slow path, which involves activating the throttle valve (electronic throttle), while the other is a fast path, which involves varying the timing angle and suppressing individual cylinders. The slow path, also called the charge path, is responsible for stationary operation with an optimum air ratio (lambda). The faster path is called the firing angle path and is responsible for dynamic torque adjustment. Fuel/Ignition Diagnosis & Repair Page 9.21

150 Additional DME Functions & Special Control Systems Purpose of Torque Flow From a sufficient number of measurements on the test stand, the correlations between engine speed, relative air charge and the lambda, timing angle and internal torque variables are stored in maps. This description of the engine allows us to show the correlation between engine torque and the specified control variables. That important property can therefore be used to calculate the current engine torque from the active control variables and calculate the necessary control variables for the desired setpoint torque. The measurements are evaluated using an optimization program, whereby two maps are of significance. The first map contains the optimum timing angle for the current engine operating state, which results from the relative air charge and engine speed. A stoichiometric mixture is also required. For commercially available fuel, this produces a stoichiometric mixture ratio of ml/mk Combustion then takes place when lambda equals 1. The optimum torque, which is stored in the second map, is set at this timing angle. This setting can be used to achieve the maximum internal torque under standard conditions. Notes: Page 9.22 Fuel/Ignition Diagnosis & Repair

151 Additional DME Functions & Special Control Systems Calculation of Required Values Calculation of the Timing Angle The basic timing angle is calculated from the current operating conditions of the engine. This means that the basic timing angle is essentially determined by the current charge and the resultant engine load condition, the current engine speed and the mixture composition. Changed operating conditions while starting the engine and during the engine warm-up phase are taken into account using an absolute specification or a correction term. In addition, the basic timing angle can still be retarded by knock control. The following applies therefore to the base timing angle when starting the engine: Base timing angle = start-up timing angle and in all other operating points: Base timing angle = basic timing angle + warm-up timing angle + knock control intervention The base timing angle is identical to the most advanced timing angle. The required timing angle is the output for implementing the expected torque. The required timing angle is limited to the most advanced or most retarded timing angle. In the event of active torque interventions (e.g. Tiptronic, Traction Control, Porsche Stability Management, etc.), the timing angle achieved as a result is used as the actual timing angle. If there is no requirement for torque intervention, the base timing angle is used. The timing angle that is used is still adjusted by a phase error and is limited to the possible values in the particular system. This results in the current timing angle. Timing Angle (path 1) Using the current values for engine speed and relative air charge, the optimum timing angle is determined from the timing angle map and serves as an intermediate variable for the next calculation. Now, the delta timing angle by which the timing angle for the specified lambda must be changed is determined. By changing the timing angle, you get the optimum indicated torque for the real lambda. However, this torque is not necessarily the engine torque requested by the torque coordinator. For this reason, the internal torque supplied by the engine can still be influenced further. The effect of this change in the timing angle can be shown easily by introducing a timing angle efficiency level. Fuel/Ignition Diagnosis & Repair Page 9.23

152 Additional DME Functions & Special Control Systems Air Charge (path 2) Torque can be influenced via the air charge - in other words: the calculation of the throttle valve angle (electronic throttle) control variable. The lambda, timing angle and timing angle efficiency level are assumed to be constant. To determine the required throttle valve angle, a physical description of the air charge is required. The basic calculation of the torque structure is carried out using 2 maps and 3 characteristics. These are determined from the data obtained during an automated measurement process on a roller-type test stand and the subsequent application of an optimization program. Torque Coordination Using the Charge Path and Timing Angle Path Different torques can be specified for the timing angle path (path 1) and the charge path (path 2) in the DME. The charge torque is a fictitious variable here. If a higher torque is required using the charge path than using the timing angle path, a higher air mass can be set. The current air mass also affects the timing angle path through the basic variables. To set the required torque of the timing angle path, the timing angle must be retarded when a higher air mass is used. This intentional loss of efficiency can be used to achieve a dynamic threshold (torque changes by adjusting the timing angle, e.g. idle speed control) or even for heating the catalytic converter quickly. Torque Optimization The term torque optimization is used to describe the significance of the torque interface of the DME. A calculation model of a gasoline engine is used here to determine the effective torque. The parameters that determine the model behaviour are determined by an algorithm in such a way that the difference between the real engine and the model are minimal. The following functions are used for detecting data: Crankshaft position and engine speed Camshaft position Hall sender signal Engine temperature Battery voltage Air charge (general) Load Calculation The relative air mass is also needed in order to calculate the cylinder charge (i.e. the current air mass in the cylinder). It must be known in order to calculate the injection mass, for example. Apart from the timing angle, it is also the main variable for influencing the engine torque and is therefore used as a control variable for calculating the torque structure. As it cannot be measured directly, it must be calculated from the available measurement signals using a model. The main variable for creating the charge model is the air mass detected using the mass air flow (MAF) sensor (or the pressure sensor in newer systems). The purpose of the load calculation (load prediction) is to predict the air charge at the time of the gas cycle. For this purpose, the interaction of the mass air streams flowing in and out and the intake manifold pressure must be evaluated for future times using a numeric procedure. To take the mass flowing in into account correctly here, the future throttle valve angle must be known or at least estimated. Notes: Page 9.24 Fuel/Ignition Diagnosis & Repair

153 Additional DME Functions & Special Control Systems Thermal Management V8 Thermal management Panamera and Cayenne MY 2011 and later The thermal management function controlled by the DME control unit covers 3 main areas, namely temperature control and heat distribution between: Combustion engine Passenger compartment and Tiptronic S Map-controlled coolant temperature control takes place by suppressing the coolant flow in the warm-up phase. This means that the thermostat is a hot thermostat that would open slowly and the engine would heat up quickly. The heating element heats up the wax pellet in the thermostat and opens the thermostat faster allowing the engine management to control the engine temperature. The operating temperature is regulated between 201 F. (94 C.) and 221 F. (105 C.) when the engine is warm. Goals Bringing components to the optimum operating temperature quickly (reduced friction) Reduced engine and transmission friction through mapbased control of the operating temperature Meeting the comfort requirements of passengers The cooling system ensures that the engine runs at a favorable operating temperature for optimum and permanent high performance. A further advantage is provided by the low fuel consumption and emission values, since all components reach the optimum operating temperature more quickly. The closed-loop-controlled thermal management system controls thermal processes in the vehicle with the aim of achieving optimum efficiency for the overall system and bringing all components to their optimum operating temperature quickly. The three main areas of the thermal management system are heat distribution between combustion engine, transmission and passenger compartment. The basic goal is to ensure that all components reach their optimum operating temperature as quickly as possible and to also meet the comfort demands of passengers by heating up the cabin quickly. At low temperatures and for cold engine starts in particular, it is important to manage the low amount of available heat in the best possible way. Efficient use of the available heat helps to save fuel, reduced CO2 emissions and comply with strict emission regulations. Cayenne models with Tiptronic S (optional for Cayenne) are equipped with thermal management for the transmission. Here also, the aim is to reach the optimum operating temperature as quickly as possible in order to minimize friction losses. For this purpose, the heat exchanger of the cooling system for the 8-speed Tiptronic S is connected to the engine cooling system. If necessary, this allows the heat of the engine coolant, which is heated up more quickly, to be used to bring the transmission up to its operating temperature. Advantages of Thermal Management with Electric Control of the Coolant Thermostat by the DME Control Unit Map-controlled coolant temperature regulation by suppressing coolant flow in the warm-up phase Faster warming-up of engine and transmission Reduced engine and transmission friction Lower fuel consumption (-1.5 % in the NEDC) Reduced emissions The cooling system is part of the thermal management system and has two circuits which can be regulated depending on the coolant temperature. This is done by an electric, map-controlled and deactivatable thermostat. The thermostat permits automatic, demand-based suppression of the coolant flow when the engine is cold (cold start). As a result, the engine heats up more quickly (Start Stop operating condition is reached more quickly) and friction, fuel consumption and pollutant emissions are reduced in the warm-up phase. NEDC New European Driving Cycle (yellow) Pink New Cayenne with thermal management Light blue Old Cayenne without thermal management C Coolant temperature T Time in seconds km/h Vehicle speed Fuel/Ignition Diagnosis & Repair Page 9.25

154 Additional DME Functions & Special Control Systems Depending on the increase in engine temperature, the coolant flow through the engine (small circuit) is then activated during warming up. After this, the coolant radiator is activated (large circuit) depending on the engine operating point and based on a map stored in the engine control. The map control of the thermostat then regulates the coolant temperature between 201 F. (94 C.) and 221 F. (105 C.), depending on load, and thus ensures optimum friction conditions in the engine that are adapted to the respective load point. This thermal management system made it possible to reduce fuel consumption by up to 1.5 %. Two temperature sensors are used in the engine cooling system to control the thermal management system Figure 2 - A further temperature sensor is located on the left coolant hose of the radiator Outlet. E - Electrical connection on the coolant thermostat. As a result of the standing coolant after the cold start, the engine heats up more quickly in the warm-up phase. Figure 1 - The coolant temperature sensor is installed on the cylinder head at the rear right. Demand-based electrical map control of the thermostat allows the coolant temperature to be regulated between 201 F. (94 C.) and 221 F. (105 C.), depending on load. Page 9.26 Fuel/Ignition Diagnosis & Repair

155 Additional DME Functions & Special Control Systems Thermostat Opening The main advantage of the map-controlled thermostat, which is electrically heated by the DME control unit, is that it is possible to regulate a specific temperature. The thermostat is fully closed when the engine is cold. Fully Open The 2nd temperature sensor on the coolant hose permits early detection of when the thermostat starts to open and allows the necessary corrective action if necessary in order to achieve the setpoint temperature. The DME control unit adapts the opening behavior of the thermostat in order to compensate for tolerances and aging. The setpoint temperature in normal operation is 221 F. (105º C.); the setpoint temperature is reduced to 201 F. (94º C.) in Sport mode and in the event of certain faults. Bypass Open Electrical preheating makes it possible to quickly open the bypass for the small engine circuit in a controlled manner during the warm-up phase. This is achieved by providing more or less electrical heating close to the wax elements. The controlled bypass circulation in the small engine circuit allows the engine to reach operating temperature more quickly and in a uniform way. Notes: Fuel/Ignition Diagnosis & Repair Page 9.27

156 Additional DME Functions & Special Control Systems 9x1 Thermal Energy Management The 9x1s features a comprehensive thermal management system for the first time. The advantages achieved compared with the previous model are as significant as the possible operating states of the thermal management system are varied. Thermal management not only involves the engine, but also the transmission and heating. Objective Networking of all relevant heat sources in order to: Reduce consumption by controlling the heat flows during all phases (up to 2%) Reduce emission values Reduce internal friction in the engine and transmission Increase performance Improve aerodynamics by doing away with air intakes in the underbody panelling, this also increases the top speed up to 189 mph (304 km/h) Increase heating comfort Enhance the OBD functions Coolant Temperature Level, Engine Picture above: Comparison of coolant temperature level between 9x1 and 997 (2) Performance enhanced by reducing the coolant temperature to 185 F. (85 C.) during periods of increased operating load, or by actuating a map-controlled thermostat when Sport/Sport Plus mode is activated. The speed with which the operating temperature is reached is achieved by way of an innovative rotating piston valve that is actuated by the DME control unit according to a control map. The engine is at operating temperature when an engine coolant temperature of 221 F. (105 C.) is reached. Operating Modes The operating modes of the thermal management system can be categorized as follows for the 9x1: 1. Operating mode: Warm-up a) Measures aimed at reducing fuel consumption Specific channelling of available heat flows to operating fluids and components that are relevant to consumption Reduces heat losses to a minimum, accelerates warm-up b) Increased heating comfort Specific channelling of the available heat flows into the passenger cell 2. Operating mode: At operating temperature Reduces consumption by increasing the coolant temperature (221 F./105 C.) 3. Operating mode: Cooling Optimizes performance by reducing the coolant temperature (185 F./85 C.) Reduces the cooling of operating fluids and components relevant to consumption after the engine is switched off until it is started again Page 9.28 Fuel/Ignition Diagnosis & Repair

157 Additional DME Functions & Special Control Systems Overview of the Engine Cooling System From the Front (991) Shut-off Valves The coolant throughput to different components is controlled in the cooling system of the 9x1 by way of the mapcontrolled thermostats (3) on the one hand and electropneumatically actuated valves (7) on the other. Electropneumatic Switching Valves 1 Connection for heat exchanger and expansion tank 2 Coolant return line for coolant radiator 3 Map-controlled thermostat 4 Mechanical coolant pump 5 Coolant return line forcylinder banks 1 and 2 6 Coolant supply line for cylinder banks 1 and 2 7 Coolant shut-off valve (electropneumatically actuated) 8 Coolant supply line for coolant radiator 9 Coolant return line for engine oil heat exchanger 10 Coolant supply line for engine oil heat exchanger 11 Engine vent line The thermal management system features electropneumatic shut-off valves for the following components: Engine coolant shut-off valve (7) Heat exchanger Gear oil heat exchanger ATF heat exchanger (Porsche Doppelkupplung [PDK] only) Note! The coolant temperature gauge in the instrument cluster shows 194 F. (90 C) at normal operating temperatures 185 F F. (85 C C.). Notes: Fuel/Ignition Diagnosis & Repair Page 9.29

158 Additional DME Functions & Special Control Systems Vacuum System The 991 has a maximum of eight electropneumatic valves in total, four of which belong to the thermal management system. Vacuum Lines, Installation Position Cylinder Bank 2 (991) Further electropneumatic valves are used to switch: the tuning flap (991 S only), the air cleaner flap, the sound symposer and the sports exhaust system flap (optional). Overview of the Vacuum System See blue arrow in following picture. * 991 S only ** Only with the sports exhaust system (optional) *** Only with the Porsche Doppelkupplung (PDK) (optional) 1 Solenoid valve for shut-off valve for heat exchanger 2 Shut-off valve for heat exchanger (pneumatic) 3 Unfiltered air connection, solenoid valve for exhaust flaps (exhaust flaps only with sports exhaust system, optional) 4 Solenoid valve for engine coolant shut-off valve 5 Solenoid valve for tuning flap switching valve (991 S only) 6 Switching valve for tuning flap (pneumatic, 991 S only) 7 Vacuum connecting line for transmission Notes: Page 9.30 Fuel/Ignition Diagnosis & Repair

159 Additional DME Functions & Special Control Systems Vacuum Lines, Installation Position on Air Cleaner Housing/Cylinder Bank 2 (991) Diagnosing Faults in the Vacuum System (991) See blue arrow in following picture. 1 Solenoid valve for sound symposer switching valve 2 Solenoid valve for air cleaner flap switching valve 3 Solenoid valve for heat exchanger shut-off valve The solenoid valves for the sound symposer switching valve and for the air cleaner flap are installed on the right behind the air cleaner box. 1 Switching valve for exhaust flaps (pneumatic, sports exhaust system [optional] only) 2 Map-controlled thermostat 3 Switching valve for engine coolant shut-off valve The electric solenoid valves in the vacuum system are fully diagnosable (short circuit/open circuit); electrical faults result in an entry in the DME control unit and, if applicable, in the PDK control unit. Leaks in the vacuum system are detected through the malfunctioning of pneumatic switching valves and the associated effects. The DME control unit cannot, however, output an unequivocal fault message in the event of leaks in the vacuum system because there are too many different vacuum components connected. For example, a leak in the pneumatic switching valve for the tuning flap could generate a fault message about the cooling system. Background knowledge on electropneumatically controlled valves The pneumatic valves are switched in steps, in other words they are either fully closed or fully open. They can, in principle, also be operated continuously, but the compression properties of air mean that this cannot be done with any precision. Background knowledge on electronically controlled actuators Consequently, electrical actuators are currently used for precise, continuous control of valves; these have the following disadvantages compared with pneumatic valves: Higher production costs Higher weight More complicated activation A further advantage of the electrically actuated valves is their better diagnostic capabilities. Feedback devices (potentiometers) are attached to the drive links and communicate the position detected by the actuator directly to the control unit, which also makes for easy and precise control of the relevant component. Fuel/Ignition Diagnosis & Repair Page 9.31

160 Additional DME Functions & Special Control Systems Engine Coolant Shut-off Valve The engine coolant shut-off valve (electropneumatically actuated) is designed as a rotating piston valve and is used, among other things, to reach the engine operating temperature faster during the warm-up phase. The coolant throughput is increased as required by closing the electropneumatically actuated coolant shut-off valve via the DME control unit. Closing the engine coolant shut-off valve (vacuum present) largely prevents the coolant circulating in the engine, even though the impeller of the mechanically driven coolant pump is turning. This applies as long as the map-controlled thermostat is closed. The coolant in the engine means that the combustion engine reaches its operating temperature much faster than in systems without thermal management, however the coolant pressure also increases along with the engine speed. If the engine coolant shut-off valve is closed when the thermostat is open, the coolant throughput in the coolant radiators increases. The engine coolant shut-off valve must be open above 3,000 rpm as high pressures would otherwise build up in the cooling system, possibly resulting in leaks and damage to the cooling system. 991 shown above. The engine coolant shut-off valve is kept closed in the following operating modes by the DME control unit: Heating phase (not USA) Maximum cooling Heating engine boost mode Diagnosis The evaluation electronics can detect mechanical faults in the map-controlled thermostat and engine coolant shut-off valve by evaluating the temperature signals, but cannot identify which of the specified components is defective. A thermostat or engine coolant shut-off valve that is stuck closed will result in an entry in the fault memory after a diagnostic routine. The engine coolant shut-off valve is closed as a function of: Setpoint engine coolant temperature Engine coolant temperature Coolant temperature at the radiator outlet Gear oil and ATF temperature (Porsche Doppelkupplung [PDK] only) Heating request to the air conditioning system Engine power Engine speed Ambient air temperature Page 9.32 Fuel/Ignition Diagnosis & Repair

161 Additional DME Functions & Special Control Systems Thermal Management for Heat Exchanger Coolant flows through it during: Heating requests Maximum engine cooling requests Shut-off Valve for Heat Exchanger The shut-off valve for the heat exchanger is opened via the air conditioner control unit when the driver requests heat. The engine coolant shut-off valve, which is closed when the engine is not yet at operating temperature, ensures that sufficient hot coolant is available even after a very short time in order to heat the passenger compartment. When the passenger compartment no longer needs to be heated, the shut-off valve for the heat exchanger is closed again so that the combustion engine can reach its operating temperature faster. The shut-off valve for the heat exchanger is also automatically opened when a request for maximum engine cooling is sent via a CAN message from the DME control unit to the air conditioner control unit in order to further reduce the coolant temperature in the engine and in this way prevent damage to the engine and transmission. Closing the engine coolant shut-off valve below 1,800 rpm increases the flow of coolant in the heat exchanger, but also increases the heating output considerably (heating boost mode). Diagnosis 991 shown above. Notes: Fuel/Ignition Diagnosis & Repair Page 9.33

162 Additional DME Functions & Special Control Systems Thermal Management for Gear Wheel Set Porsche Doppelkupplung (PDK) and Manual Transmission) Gear Oil Heating To heat up the gear oil faster, the shut-off valve for the gear oil heat exchanger (1) is opened during the engine warm-up phase as soon as the coolant has reached a temperature of 158 F. (70 C.) and is therefore hotter than the gear oil. The coolant then flowing into the gear oil heat exchanger (2) boosts heating of the gear oil to the setpoint temperature of 194 F. (90 C.). The friction in the gear wheel set is reduced faster (the viscosity characteristics of the oil improve when the oil temperature increases), shifting comfort is increased and fuel consumption is reduced. The shut-off valve is closed (vacuum present) as soon as the setpoint gear oil temperature of 194 F. (90 C.) is reached. This prevents excessive heating of the gear oil. The specified temperatures are for guidance only and may vary depending on the operating condition and variant. Gear Wheel Cooling The disc valve is opened again if the gear oil temperature increases beyond the setpoint temperature and beyond the temperature of the coolant; the purpose of this is to cool the gear oil (component protection). Gear Oil Pump 1 Pneumatically actuated shut-off valve for gear oil heat exchanger 2 Gear oil heat exchanger A temperature sensor (see photo on the next page) is installed close to the gear oil heat exchanger (which is attached to the transmission housing) that continuously detects the gear oil temperature and communicates this information to the DME control unit. 1 Gear oil pump (installation position) 2 Gear oil heat exchanger 3 Gear oil temperature sensor (NTC) The cooling oil is supplied to the gear wheel set via a Wankel pump (1) installed directly at the heat exchanger (2) and driven by a pinion shaft. This way that the supply of cooling oil to the gear wheel set is speed-dependent. Page 9.34 Fuel/Ignition Diagnosis & Repair

163 Additional DME Functions & Special Control Systems Diagnosis Thermal Management for the Porsche Doppelkupplung (PDK) The Porsche Doppelkupplung (PDK) in the 9x1 features an additional ATF heat exchanger (1) that is integrated in the thermal management system for the entire vehicle by way of sensors. The ATF temperature sensor is necessary for this. The DME control unit receives its values via the PDK control unit. The ATF heat exchanger (1) is mounted on the PDK housing. Its purpose is to heat the ATF faster (and cool it if necessary) or to cool the oil-cooled and oillubricated double-clutch transmission. phase as soon as the coolant has reached a temperature of 158 F. (70 C.) and is therefore hotter than the ATF. The coolant then flowing into the ATF heat exchanger (1) boosts the heating of the ATF to the setpoint temperature of 185 F. (85 C.). The friction losses of the moving parts in the hydraulic area of the transmission are reduced (the viscosity characteristics of the oil improve when the oil temperature increases), shifting comfort is increased and fuel consumption is reduced. If the setpoint ATF temperature of 185 F. (85 C.) is reached, the DME control unit actuates the solenoid valve for the ATF heat exchanger (2) and the solenoid valve directs vacuum to the pneumatic shut-off valve (3). The shut-off valve closes and prevents any more coolant flowing into the heat exchanger. This prevents excessive heating of the ATF. The specified temperatures are for guidance only and may vary depending on the operating condition. Notes: ATF Heating To heat up the ATF faster, the shut-off valve for the ATF heat exchanger (3) is opened during the engine warm-up Fuel/Ignition Diagnosis & Repair Page 9.35

164 Additional DME Functions & Special Control Systems ATF Cooling Operation of the double-clutch transmission results in greater heating of the ATF than of the gear oil. The disc valve is opened again if the ATF temperature increases beyond the setpoint temperature and the engine coolant temperature is below the temperature of the gear oil. The coolant circulating in the ATF heat exchanger cools the gear oil (component protection). Component Protection for the Porsche Doppelkupplung (PDK) Map-controlled Thermostat The map-controlled thermostat is an insertion mapcontrolled thermostat with a heating element. The mapcontrolled thermostat can be energised via the DME control unit. The flow of current through the heating element (electric resistor) causes it to heat up, which in turn influences the expansion element in the thermostat and enables it to be opened. Actuation by the DME control unit is performed by means of pulse width modulation, which means that the coolant temperature level can be continuously controlled. A message appears in the instrument cluster (first white, then red transmission temperature warning) as a safety measure if the transmission overheats. The DME control unit additionally reduces the torque until the ATF temperature reaches a non-critical value again. The warning message then disappears. Diagnosis Notes: Page 9.36 Fuel/Ignition Diagnosis & Repair

165 Additional DME Functions & Special Control Systems The usual coolant temperature when the engine of the 991 (S) is at operating temperature is 221 F. (105 C); it is reduced to 185 F. (85 C.) during sporty driving and in Sport/Sport Plus mode by opening (energising) the thermostat. This supports a performance-oriented driving style. The DME control unit can also have the thermostat closed by switching off the heating current. The coolant temperature must be less than 216 F. (102 C.) for this to be possible. The map-controlled thermostat starts to open at 216 F. (102 C.) +/- 36 F. (2 C.) when de-energized and is fully open at 239 F. (115 C.). The coolant temperature is measured by the engine coolant temperature sensor and the radiator outlet coolant temperature sensor and transmitted to the DME control unit. Diagnosis The map-controlled thermostat is diagnosable. Electrical faults and detection of a thermostat that is stuck open result in an entry in the fault memory, the OBD indicator light comes on and the warning message Cooling system error appears in the instrument cluster. A thermostat or an engine coolant shut-off valve that is stuck closed is also indicated in the instrument cluster by way of the warning message Cooling system error, but the OBD indicator light does not come on. The evaluation electronics cannot yet correctly identify whether the mapcontrolled thermostat or the coolant shut-off valve is defective. As of MY 12/13 it will be possible to correctly identify which of the specified components is defective with the help of PIWIS Tester II using the Short test function. The DME control unit energizes the heating element (resistor) in the map-controlled thermostat: In the lower and medium load range in order to limit the coolant temperature in the engine to 221 F. (105 C.). With an increased load requirement as well as during operation in Sport and Sport Plus mode in order to reduce the engine coolant temperature to 185 F. (85 C.). The cooler cylinder walls result in higher density of the oxygen content in the combustion chamber. The improved charging enhances the performance of the combustion engine. If necessary to prevent critical gear wheel oil and ATF (Porsche Doppelkupplung [PDK] only) temperatures. The heat exchanger can also be activated for this purpose. The following parameters are used for diagnosis: Setpoint engine coolant temperature Engine coolant temperature Coolant temperature at the radiator outlet Engine speed Mass air flow Deceleration phases Vehicle speed Ambient temperature 991 shown above. Fuel/Ignition Diagnosis & Repair Page 9.37

166 Additional DME Functions & Special Control Systems Engine Coolant Temperature Sensor The engine coolant temperature sensor (NTC) is installed in cylinder bank 1 near the third cylinder and is designed as a temperature-dependent resistor. Diagnosing the Engine Coolant Temperature Sensor (cross-check diagnosis) The purpose of cross-check diagnosis is to check that temperature sensors are working correctly. The control unit compares the temperature values of different sensors and checks them for plausibility. The following temperatures are compared when checking the engine coolant temperature sensor: Engine coolant temperature Engine oil temperature Intake air temperature Ambient temperature Step 1 When an engine is started after the ignition has been off for more than 8 hours, the specified temperature values are compared. The temperature values must not deviate by more than a certain value (depending on when the ignition was switched off). A suspected fault is set if the deviation is too great, but this must be confirmed in Step 2. The sensor signal is used for: DME control (ignition/injection system) Actuating the engine coolant shut-off valve Actuating the map-controlled thermostat Actuating the engine compartment purge fan Checking the oil temperature sensor/oil temperature Air conditioning control Diagnosing the engine coolant shut-off valve Cross-check diagnosis Step 2 The check is repeated if a journey during which the vehicle travels at more than 16 mph (25 km/h) for a total of 45 seconds takes place within 6 minutes of the engine starting. The relevant fault is written to the fault memory if the temperature of the suspected sensor continues to deviate by too much (difference > 77 F. (25 C.). The suspected fault is dismissed and no fault is entered in the fault memory if the deviation in temperature of the suspected sensor is no longer as great. The suspected fault is dismissed and no fault is stored in the fault memory if the vehicle is not driven within 6 minutes of starting the engine. The following fault causes can be detected with the help of the engine coolant temperature sensor: Engine coolant temperature sensor faulty Thermostat/thermostat housing seal/thermostat housing faulty Air in the cooling system Oil temperature sensor faulty Fault in DME Page 9.38 Fuel/Ignition Diagnosis & Repair

167 Additional DME Functions & Special Control Systems Radiator Outlet Coolant Temperature Sensor The radiator outlet coolant temperature sensor can detect the following faults: Radiator outlet coolant temperature sensor faulty Engine coolant temperature sensor faulty Engine coolant shut-off valve jammed Radiator air intake covered with debris Intake air temperature sensor faulty Note! Unapproved wheel retrofits (wheel diameter too large) can result in a reduced air-flow rate at the coolant radiators. The radiator outlet coolant temperature sensor is located on the coolant pipe at the radiator outlet towards the engine on the vehicle underbody. The temperature information is transmitted to the DME control unit. The DME control unit uses the plausible signal to control the thermal management system. The sensor signal is used for: Actuating the coolant radiator fan as a function of the coolant temperature as a function of the setpoint engine coolant temperature Testing the function of the map-controlled thermostat/ engine coolant shut-off valve Diagnosis Diagnosis The DME control unit compares the following values when checking the radiator outlet coolant temperature sensor: Engine coolant temperature Intake air temperature sensor Operating Modes The thermal management system is influenced by a number of different operating conditions. For that reason, only the most significant conditions are described here. We will start with a few generally valid statements regarding the cooling system in the 991: The coolant cooling system for the engine is designed in two parts. The two parts are kept separate by the closed engine coolant shut-off valve. Coolant is continuously passed through the engine oil heat exchanger while the engine is running. As well as its primary task of cooling the engine, the cooling system is also used to heat/cool transmission oils. An ATF heat exchanger (Porsche Doppelkupplung [PDK] only) and gear oil heat exchanger are integrated for this purpose. Only vehicles intended for extremely hot countries have an additional center radiator. (Not for USA) All solenoid valves are open when de-energized, i.e. all pneumatic valves are pressurized and therefore open. Notes: Fuel/Ignition Diagnosis & Repair Page 9.39

168 Additional DME Functions & Special Control Systems First Operating Condition: Engine cold/off The heating boost mode function enables faster heating of the passenger compartment. The heating boost mode function also has the task of preventing the passenger compartment from cooling down, even with low load requirements and very low outside temperatures. 1 Side radiator 2 Center radiator, variants for extremely hot countries only (Not for USA) 3 Heat exchanger 4 Disc valve, vacuum-controlled 5 Comfort valve 6 Coolant expansion tank 7 Engine oil heat exchanger 8 ATF heat exchanger (Porsche Doppelkupplung [PDK] only) 9 Gear oil heat exchanger 10 Engine coolant shut-off valve 11 Map-controlled thermostat 12 Coolant pump (mechanical) 13 Engine coolant temperature sensor 14 Coolant temperature sensor, radiator outlet Second Operating Condition: Heating boost mode Ambient temperature < 32 F. (0 C.) Coolant temperature < 203 F. (95 C.) Heating request present n < 2,000 rpm Coolant pressure < 14.5 psi (1 bar) In addition to the thermostat, the engine coolant shut-off valve (10) also stays closed up to an engine speed between 1,600 and 2,000 rpm when the ambient temperature < 32 F. (0 C.), coolant temperature < 203 F. (95 C.) and a maximum heating request is present. The closed engine coolant shut-off valve increases the coolant throughput in the heat exchanger (3) by approx. 60% compared with operation with the engine coolant shut-off valve open. The engine coolant shut-off valve is opened once the coolant temperature rises above 203 F. (95 C.). Coasting mode (Porsche Doppelkupplung [PDK] only) is an exception. Heating boost mode remains active during coasting when outside temperatures are below 32 F. (0 C.) and a maximum heating request is present. The mapcontrolled thermostat (11) is closed so that the coolant volume to be heated can reach its temperature faster. Note! The procedure for filling and bleeding the cooling system must be followed as outlined in the Workshop Manual to prevent damage to the engine and transmission. Comfort Valve Closed No coolant flows into the expansion tank (6) because the comfort valve (5) only opens the return lines from the two coolant radiators and engine to the expansion tank when the coolant pressure exceeds approx psi (1 bar). The closed comfort valve (5) ensures that there is less coolant to be heated at pressures below 14.5 psi (1 bar), which means that the coolant temperature can increase faster. Any air bubbles in the cooling system cannot be automatically bled because the comfort valve does not open. During a pressure increase with air inclusions in the cooling system, the trapped air is compressed but the comfort valve remains closed. This can result in overheating damage to the engine and transmission. Page 9.40 Fuel/Ignition Diagnosis & Repair

169 Additional DME Functions & Special Control Systems Third Operating Condition: Cold start/warm-up Ambient temperature 59 F F. (15 C C.) Coolant temperature < 122 F. (50 C.) Heating request n <= 3,000 rpm Coolant pressure > 14.5 psi (1 bar) Coolant throughput only takes place between the engine, engine oil heat exchanger (7) and, in the event of a heating request, the heat exchanger (3) so that the temperature losses of the coolant are very low and the coolant heats up very quickly in the engine. The disc valve (4) of the heat exchanger (3) is opened in the event of a heating request so that coolant can flow into the heat exchanger. Engine Coolant Shut-off Valve Control When the starting temperature (ambient temperature) is between 59 F F. (15 C C.), the engine coolant shut-off valve (10) remains closed until the coolant in the engine has reached a temperature of 122 F. (50 C.) in order to heat the engine faster. The engine coolant shut-off valve (10) remains open if the ambient temperature exceeds 95 F. (35 C.). 1 Side radiator 2 Center radiator, variants for extremely hot countries only (Not for USA) 3 Heat exchanger 4 Disc valve, vacuum-controlled 5 Comfort valve 6 Coolant expansion tank 7 Engine oil heat exchanger 8 ATF heat exchanger (Porsche Doppelkupplung [PDK] only) 9 Gear oil heat exchanger 10 Engine coolant shut-off valve 11 Map-controlled thermostat 12 Coolant pump (mechanical) 13 Engine coolant temperature sensor 14 Coolant temperature sensor, radiator outlet The engine coolant shut-off valve opens when an engine speed of 3,000 rpm is exceeded in order to prevent excessively high pressures in the cooling system. The map-controlled thermostat (11) is always closed during the heating phase. Comfort Valve Open The slight increase in the coolant temperature causes the coolant pressure to exceed 1 bar and the spring-loaded comfort valve (5) to open. The return lines to the expansion tank are now opened and approx. 1.3 gal. (5 liters) of additional coolant are introduced into the cooling system. Notes: Fuel/Ignition Diagnosis & Repair Page 9.41

170 Additional DME Functions & Special Control Systems Fourth Operating Condition: Warm-up Ambient temperature >= 32 F. (0 C.) Coolant temperature > 122 F. (50 C.) Heating request Fifth Operating Condition: Transmission Heating Coolant temperature > 113 F. (45 C.) < 194 F. (90 C.) Gear wheel oil temperature < 194 F. (90 C.) ATF temperature < 185 F. (85 C.) (Porsche Doppelkupplung [PDK] only) The engine coolant shut-off valve (10) remains open even at engine speeds below 3,000 rpm, regardless of whether or not a heating request is present, because the ambient temperature is high enough to heat the passenger compartment with the available coolant throughput and the available coolant temperatures. The coolant in the small cooling system continues to heat up very quickly due to the still-closed thermostat (11) and the closed shut-off valves for gear oil cooling (9) and ATF cooling (8, Porsche Doppelkupplung [PDK] only). The shutoff valves for the gear oil heat exchanger and ATF heat exchanger can open from a minimum coolant temperature of F. (45-90 C.), depending on the variant and operating condition. 1 Side radiator 2 Center radiator, variants for extremely hot countries only (Not for USA) 3 Heat exchanger 4 Disc valve, vacuum-controlled 5 Comfort valve 6 Coolant expansion tank 7 Engine oil heat exchanger 8 ATF heat exchanger (Porsche Doppelkupplung [PDK] only) 9 Gear oil heat exchanger 10 Engine coolant shut-off valve 11 Map-controlled thermostat 12 Coolant pump (mechanical) 13 Engine coolant temperature sensor 14 Coolant temperature sensor, radiator outlet Notes: Page 9.42 Fuel/Ignition Diagnosis & Repair

171 Additional DME Functions & Special Control Systems The shut-off valves for the gear oil heat exchanger (9) and ATF heat exchanger (8, Porsche Doppelkupplung [PDK] only) are opened within a coolant temperature range between 113 F. (45 C.) and 194 F. (90 C.). When the shut-off valves open depends on the operating condition/variant. The coolant boosts the heating of the gear oil and ATF (Porsche Doppelkupplung [PDK] only) in this condition. Sixth Operating Condition: At operating temperature Driving program: Normal (moderate driving) Coolant temperature = 221 F. (105 C) The shut-off valve for the gear oil heat exchanger (4) is closed once the setpoint gear oil of 194 F. (90 C.) is reached in order to prevent overheating of the gear oil. The shut-off valve for the gear oil heat exchanger (4) is opened again if the gear oil temperature falls below 158 F. (70 C.) in order to heat the gear oil again. This can occur especially during trips at very low ambient temperatures. Porsche Doppelkupplung (PDK) only: The shut-off valve for the ATF heat exchanger is closed once the setpoint gear oil of 185 F. (85 C.) is reached in order to prevent overheating of the ATF. The shut-off valve for the ATF heat exchanger is opened again if the ATF temperature falls below 158 F. (70 C.) so that the coolant can heat the oil again. The specified temperature values for closing the shut-off valves of the transmission heat exchangers vary depending on the operating condition/variant. The map-controlled thermostat (11) automatically begins to open at approx. 216 F. (102 C), providing a small gap for the coolant. From now on, the coolant is cooled by the coolant radiators (1, 2) in the front end. The setpoint coolant temperature in the engine is 221 F. (105 C) with a moderate driving style and Sport/Sport Plus mode deactivated. Shut-off valve for gear oil heat exchanger and ATF heat exchanger (Porsche Doppelkupplung [PDK] only) The shut-off valves for the gear oil and ATF heat exchangers are only opened in this operating condition if the gear oil temperature and/or the ATF temperature are too low (e.g. in cold countries), or their temperatures are higher than that of the engine coolant, resulting in cooling of the heat exchangers at the transmission (8, 9). Fuel/Ignition Diagnosis & Repair Page 9.43

172 Additional DME Functions & Special Control Systems Seventh Operating Condition: At operating temperature Driving program: Sport/Sport Plus, or: performanceoriented driving in the Normal program Coolant temperature approx. 185 F. (85 C.) Eighth Operating Condition: Maximum cooling Coolant temperature > 221 F. (105 C.) 1 Side radiator 2 Center radiator, variants for extremely hot countries only (Not for USA) 3 Heat exchanger 4 Disc valve, vacuum-controlled 5 Comfort valve 6 Coolant expansion tank 7 Engine oil heat exchanger 8 ATF heat exchanger (Porsche Doppelkupplung [PDK] only) 9 Gear oil heat exchanger 10 Engine coolant shut-off valve 11 Map-controlled thermostat 12 Coolant pump (mechanical) 13 Engine coolant temperature sensor 14 Coolant temperature sensor, radiator outlet The coolant temperature is reduced to 185 F. (85 C.) in Sport/Sport Plus mode and with a sporty driving style in Normal mode in order to improve the performance values through improved charging. Map-controlled Thermostat The temperature reduction is achieved by heating and therefore opening the map-controlled thermostat (11). The map-controlled thermostat is completely open at an expansion element temperature of 239 F. (115 C) (does not have to correspond to the coolant temperature). Transmission Cooling The shut-off valves for the gear oil heat exchanger (9) and ATF heat exchanger (8) are additionally opened if necessary in order to reduce the operating fluid temperatures in the transmission and in this way prevent overheating of the transmission parts. If the setpoint coolant temperature at the engine and coolant outlet (depending on the operating condition) is exceeded despite the thermostat (11) being open, the engine coolant shut-off valve (10) is closed in order to increase the coolant throughput in the coolant radiators. The DME control unit opens the shut-off valve for the heat exchanger (4) via a command to the air conditioner control unit even if no heating request is present. The additional coolant and the heat emitted by the heat exchanger boost the engine cooling, and if necessary the cooling of the transmission. The coolant pressure is reduced at the same time by opening the shut-off valve for the heat exchanger. The cooling performance of the air conditioner increases in this operating condition because the passenger compartment has to be additionally cooled in order to keep the temperature in the passenger compartment constant. The DME control unit has the two electric fan motors running at maximum speed due to the high coolant temperatures at the coolant outlet. Porsche Doppelkupplung (PDK) Excess Temperature The PDK control unit can request a torque reduction from the DME control unit if transmission temperatures are too high in order to prevent the transmission from overheating. The torque reduction ceases once the transmission temperature is no longer critical. Page 9.44 Fuel/Ignition Diagnosis & Repair

173 Additional DME Functions & Special Control Systems Electric Fans for Coolant Radiators The fan motors are most efficient at n = 1,800 rpm. The drivers required for operation of the fan motors receive their commands from the DME control unit by means of PWM signals and form one unit with the fan motor. The 12V power supply for the fan motor is provided via a common line that also supplies the control unit mounted on it with current. Diagnosis 991 shown above. 1 Left coolant radiator with electric fan 2 Center coolant radiator (extremely hot countries only) (Not for USA) 3 Right coolant radiator with electric fan 4 Coolant expansion tank The coolant radiators with electric fans (1, 3) are installed on both sides in the front end of the vehicle. The variants intended for extremely hot countries are equipped with a third, center additional radiator (2) (Not for USA) without an electric fan. The functions of the electric fans are to: respond to cooling requests from the DME control (reduce engine coolant temperature, reduce air conditioner refrigerant temperature), provide maximum cooling (emergency operation, n = 2,400 rpm) if there is no DME information available, switch themselves off if there is a risk of damage from overheating. The fan motors are phase-controlled synchronous motors that are continuously actuated via separate control units (drivers). Both the control units of the radiator fans and the DME control unit can detect faults in the fans and insufficient cooling performance (radiator covered/dirty/air inclusions in the cooling system) and store them in the fault memory of the DME control unit. Electrical Faults The radiator control unit detects electrical faults. If a short circuit/open circuit occurs, a fault entry is made in the DME control unit and the fans are no longer actuated. The fan motors are operated in emergency mode (maximum speed) if the drive CAN bus is faulty or a fan control unit is not receiving any signal from the DME control unit. Measuring the current consumption not only provides a way of detecting short circuits, but also stiff/mechanically blocked fan motors. Overheating/Mechanical Faults The radiator fan control units have an integrated temperature sensor. The fan control unit can detect overheating of a fan motor by means of the signal from the temperature sensor and switch off the fan (temporarily) (component protection). The fan control unit can initiate measures (e.g. radiator fan motor working loose, operating the radiator fan at reduced speed) in the event of mechanical faults. Notes: Fuel/Ignition Diagnosis & Repair Page 9.45

174 Additional DME Functions & Special Control Systems Inputs and Outputs for Thermal Management Control Notes: Page 9.46 Fuel/Ignition Diagnosis & Repair

175 Additional DME Functions & Special Control Systems Engine Compartment Purge Fan 911 (991) The engine compartment purge fan consists of two electrically actuated fans. The fan motors can be operated at two speed settings (low and high) and are switched using two relays. Operating condition: Engine switched off If the engine has been switched off, the fans can run for up to 25 minutes in order to purge the engine compartment. Setting 2 runs at an engine temperature > 180 F. (82 C.) until the temperature in the engine compartment has fallen to < 158 f. (70 C.). The fan motors run at fan setting 1 until the engine temperature is < 113 F. (45 C.) in order to reduce the temperature further. Operating condition: Interruption of fan operation The engine compartment fan motors do not have their own control unit. There is one relay for each of the two settings (low/high). The fan motors are actuated on the instruction of the DME control unit. Actuation takes place as a function of the engine compartment temperature, which is detected by a separate engine compartment temperature sensor. The engine compartment temperature sensor is connected to the DME control unit. Another variable is the engine coolant temperature. Operating condition: Engine off, ignition on The engine compartment purge fan runs at setting 2 when the engine compartment temperature is > 162 F. (72 C.). It switches off again under these conditions when the engine temperature is < 154 F. (68 C.). Fan operation is interrupted if any of the following situations occur: Engine compartment lid open Cabriolet only: convertible top open Battery voltage < 10 volts Diagnosis The engine compartment purge fan can be diagnosed using the DME control unit. Drive-link diagnosis is possible using PIWIS Tester II. Detected faults are stored in the DME control unit. Operating condition: Engine on When the engine is running, fan setting 1 is switched on when the engine compartment temperature is > 75 F. (24 C.) and switched off again when the engine temperature is < 59 F. (15 C.). Fan setting 2 is switched on when the engine compartment temperature is > 149 F. (65 C.) or the engine coolant temperature is > 226 F. (108 C.). When the engine is running, fan setting 2 is switched off again when the engine compartment temperature is < 145 F. (63 C.) or the engine coolant temperature is < 221 F. (105 C.). Fan setting 2 is activated in the event of heavy acceleration from standstill. Activation depends on the speed with which the accelerator pedal is depressed and the accelerator pedal travel (depress fully). The same applies to the launch control start on vehicles with Porsche Doppelkupplung (PDK). Fuel/Ignition Diagnosis & Repair Page 9.47

176 Additional DME Functions & Special Control Systems Engine Compartment Purge Fan Boxster (981) There are engine compartment purge fans installed on the left and right in the engine compartment for cooling; these fans blow cool air into the engine compartment when required. Operating condition: With the engine running: The specified values correspond to an ambient temperature > 50 F (10 C). Fan setting 1 is switched: On when intake air temperature > 77 F (25 C) Off when intake air temperature < 59 F (15 C) Fan setting 2 is switched: On when intake air temperature > 149 F (65 C) Off when intake air temperature < 145 F (63 C) or On when engine compartment temperature > 160 F (71 C) Off when engine compartment temperature < 153 F (67 C) or On when coolant temperature > 226 F (108 C) Off when coolant temperature < 221 F (105 C) Operating condition: Engine switched off If the ignition was switched off at an engine compartment temperature > 113 F (45 C), the DME control unit enters an extended motor control unit run-on mode for up to 25 minutes. The engine compartment purge fans can be activated as follows in this case: The electrically activated fan motors can be operated at two speed settings (low and high). There is one relay for each of the two settings. The fan motors are activated by the DME control unit. Activation takes place as a function of the engine compartment temperature, which is reported to the DME control unit by an engine compartment temperature sensor installed at the intake manifold. Another variable is the engine coolant temperature. Note! Fan setting 1: On when engine compartment temperature > 147 F (64 C) Off when engine compartment temperature < 144 F (62 C) Fan setting 2: On when engine compartment temperature > 167 F (75 C) Off when engine compartment temperature < 147 F (64 C) Diagnosis of the engine compartment purge fans The engine compartment purge fans can be diagnosed using the DME control unit. Drive-link diagnosis is possible using PIWIS Tester II. Detected faults are stored in the DME control unit. Page 9.48 Fuel/Ignition Diagnosis & Repair

177 Additional DME Functions & Special Control Systems Auto Start Stop Auto Start Stop Function Coordination takes place in the DME control unit Auto Start Stop function can be activated and deactivated by way of a button in the center console. This function is available as soon as the engine has reached a coolant temperature of 113 F. (45 C.) and an oil temperature of 68 F. (20 C.) The combustion engine is switched off under defined conditions shortly after the vehicle comes to a stop. Fuel consumption and emissions are reduced above all in urban driving; fuel consumption in the NEDC is reduced by up to 5 %. Increased comfort for passengers, the noise level falls to zero during the stop phase. This switches off the combustion engine under defined conditions when the vehicle is at a standstill and therefore exploits potential fuel savings, e.g. unnecessary engine idling while waiting at a traffic light is prevented. The Auto Start Stop function can be deactivated and activated by way of a button in the center console. If the boundary conditions are met, the function is available as soon as the engine and battery have reached the corresponding temperature and the speed threshold of 1.2 mph (2 km/h) has been exceeded for at least 1.5 seconds. If the vehicle is stopped by brake operation and the brake pedal is held, the Auto Start Stop func - tion switches off the engine after approx. 1 second. The driver is informed about this by the green Auto Start Stop symbol in the instrument cluster. The tachometer reading falls to zero. The selector lever can remain in position D or M. The engine remains stopped even if the lever is shifted to P and N. If the engine cannot be switched off automatically, the driver is informed about this by a yellow Auto Start Stop symbol in the instrument cluster. For the driver, use of the Auto Start Stop function does not mean that he/she has to change his driving behavior. The driver does not have to perform any additional activities for an engine stop and restart. Depending on country, the Auto Start Stop function is either switched on automatically when the ignition is switched on or must be activated each time the ignition is switched on. When the Start Stop system is switched off, the indicator light in the button lights up red. Optimized criteria for frequent engine switch-off. The position of the crankshaft is detected by the differential Hall sensor on the crankshaft to permit fast starting. Battery monitoring (voltage, current, temperature). The starter is reinforced (for the increased number of starting operations). Maintains the vacuum for the brake booster. A pressure sensor on the brake booster measures the vacuum: - the engine is started again by way of a veto if the pressure falls below an applicable pressure threshold. - there is no other way of maintaining the vacuum when the engine is stopped. The criteria described were optimized and adjusted in order to ensure that the engine is switched off automatically in as many cases as possible during regular driving operation. The goal was to exploit the fuel-saving potential of the Auto Start Stop function for the driver. In order to permit realization of the Auto Start Stop function, the starter was reinforced and designed for the increased number of engine starting operations. In addition, the battery charge and aging condition as well as temperature are monitored in order to ensure the restart capability. The vehicle assists the driver when the engine is switched off by maintaining the brake pressure on uphill slopes. This was integrated as an additional function in Porsche Stability Management (PSM). This prevents the vehicle from rolling away opposite to the driving direction when the engine is switched off. The most important comfort and safety functions continue to operate even when the engine is switched off. For example, the audio and communication systems still operate and the lighting, airbag systems and PSM remain available. These functions are supplied with power from the battery for this purpose. Voltage changes when the engine stops and restarts are partially compensated for and their effects reduced. The air conditioning ensures temperature comfort. For this purpose, it uses the residual heat of the engine for heating or the residual cooling energy in the cooling system to cool the passenger compartment. If there is a risk of the passenger compartment temperature deviating significantly from the preselected value, the engine is automatically restarted in order to guarantee continued climate comfort for the passengers. Fuel/Ignition Diagnosis & Repair Page 9.49

178 Additional DME Functions & Special Control Systems Automatic Engine Stop If the prerequisites are met, the engine is stopped as soon as the vehicle comes to a stop. 1. Brake vehicle to a stop with the footbrake 2. Keep footbrake depressed or move selector lever to position P The Auto Start Stop system has detected that: at least one prerequisite is not met or at least one exception condition is present or e.g. the following faults are present: - generator fault - battery fault - DC/DC converter fault, etc. Automatic engine stop and restart readiness (function indication) If the engine was automatically switched off under the corresponding conditions, the indicator light in the multifunction display of the instrument panel lights up green. The Auto Start Stop system starts the engine: In selector lever position D, N or manually selected transmission range 1 or 2 Release footbrake or press accelerator pedal or move selector lever to position R If the vehicle is stopped by brake operation and the brake pedal is held, the Auto Start Stop function switches off the engine after approx. 1-2 seconds. The driver is informed about this by the green Auto Start Stop symbol in the instrument cluster. The tachometer reading falls to zero. The selector lever can remain in position D or M. The engine remains stopped even if the lever is shifted to P and N. Auto Engine Restart The engine is restarted when the driver releases the brake. The starting operation is supported by the direct fuel injection and ignition systems so that it can take place quickly and in a way that saves energy and protects the battery. To achieve this, the engine was supplemented by a sensor that detects the position of the crankshaft and therefore makes the information available as to which cylinder can be charged and ignited early. As a result, the engine power required for driving away is already available again after a short time. No engine stop or restart readiness (function indication) If the automatic engine stop function is not possible, the indicator light in the multi-function display of the instrument panel lights up yellow. Page 9.50 Fuel/Ignition Diagnosis & Repair If the engine cannot be switched off automatically, the driver is informed about this by a "yellow" Auto Start Stop symbol in the instrument cluster. The engine is not switched off or restarted again: if the engine has not yet reached its operating temperature if Sport mode is activated if PSM was switched off if manoeuvering or a parking operation has been detected (large steering angle), i.e. reverse gear has been engaged or the steering wheel has been turned by a large angle if the height adjustment function of the adaptive air suspension has been selected or is active if the vehicle stops on steep uphill or downhill gradients if the climate control/heating with residual heat function cannot guarantee that the set temperature can be maintained without a running engine, e.g. at very low and very high outside temperatures if the total energy requirement of the vehicle systems from the battery cannot be met (charge condition) if the rear fog light is activated if internal vehicle operations are taking place that must not be interrupted, e.g. flushing operations in the fuel system via the tank vent due to high loading of the active carbon filter if trailer operation has been detected Restarting is also prevented: if the presence of the driver is not guaranteed, i.e. driver s door is open or driver s seat belt is not fastened if the hood is open As of MY 2012 Auto Start Stop can also be used in conjunction with the manual transmission. All the driver has to do is to disengage the gear (neutral position) and remove his/her foot from the clutch pedal when the vehicle is stationary, for example in a traffic jam or in stopand-go traffic. The engine starts immediately when the clutch pedal is pressed again and the trip can be continued quickly and without delay.

179 Additional DME Functions & Special Control Systems Coasting Function Activating: Press button (1) The indicator light in the button goes off Coasting mode is activated and the engine is automatically switched off when the vehicle stops Prerequisites for coasting mode: Driving in selector lever position D Coasting mode is activated (indicator light in the button is off) Sport or Sport Plus mode is deactivated PSM is active Control cruise mode is not active Engine, transmission and battery have reached operating temperature Relaxed/economic driving style Only a slight uphill or downhill gradient Remove foot slowly from accelerator pedal 1 The Auto Start Stop button switches the Auto Start Stop function on and off and activates and deactivates coasting mode. The 9x1 models now feature the coasting function in conjunction with the Porsche Doppelkupplung (PDK). Coasting refers to operating the vehicle with the engine disengaged, for example on slight downhill gradients; the engine is operated at idle speed so that the function of the auxiliary systems (alternator, air-conditioning compressor, coolant pump, etc.) is maintained. During coasting, the kinetic and potential energy of the vehicle is directly used to overcome driving resistance. Although no fuel is used during deceleration with deceleration fuel cutoff, the vehicle is significantly decelerated. If no deceleration is desired, additional fuel must be used to cover the lost distance. Activating and Deactivating Coasting Mode Coasting mode is activated and deactivated using the Auto Start Stop button. Deactivating: Press button (1) The indicator light in the button lights up red Coasting mode is deactivated and automatic stopping of the engine is suppressed The engine is disengaged and runs at idle speed. The vehicle rolls with no engine braking effect. Coasting mode can be identified by the tachometer showing idle speed. Deactivation of the Coasting Function Automatically With a sporty driving style or if the accelerator pedal is released suddenly, coasting mode is suppressed to allow targeted use of the engine braking effect. Likewise, coasting does not occur on steep uphill gradients since the coasting phase would be very short due to the uphill gradient and no significant fuel saving is possible. Coasting mode is suppressed on steep downhill gradients since the vehicle does not slow down, despite the engine deceleration torque, and the use of deceleration fuel cutoff means that no fuel is consumed in this driving situation. Manually Press the accelerator pedal or Press the brake pedal or Press a shifting paddle or a shift button or Change gears using the selector lever Activation of the Coasting Function If coasting mode is suppressed, for example due to a sporty driving style, sudden release of the accelerator pedal or excessively low engine temperature, it can be initiated manually by shifting up a gear with the shift paddle, one of the shift buttons or the selector lever. Fuel/Ignition Diagnosis & Repair Page 9.51

180 Additional DME Functions & Special Control Systems Coasting is automatically prevented in driving situations where it no longer makes sense or would be counterproductive: if the vehicle speeds up on steep downhill gradients despite trailing throttle fuel cutoff, it is better to exploit the full fuel saving produced through trailing throttle fuel cutoff. The coasting phase would be too short in the case of steep uphill gradients. Coasting is suppressed during sporty driving so as to enable more direct responsiveness and not interrupt the flow of driving with frequent disengagement and engagement. Driving situation shown in the graphic: The driver wants to reduce the vehicle speed from 62 mph (100 km/h to 50 mph (80 km/h). a.) Vehicle without coasting function: Steady driving and then braking with engine deceleration (without fuel injection) (red curve) b.) Vehicle with coasting function: Activation coasting mode and deceleration at idle speed fuel consumption (green curve). The driving curve with coasting is more fuel efficient because the total idle speed consumption during the coasting phase (green block) is less than the total consumption during steady driving (red block). This also works with much smaller differences in speed (< 3 mph (5 km/h) and in other driving situations, e.g. slight downhill gradients. If the driver indicates a wish to decelerate by pressing the brake or intervenes manually by pressing the downshift button, the engine is re-engaged in order to use the engine's trailing throttle fuel cutoff; the fuel supply is interrupted during this process and the engine braking effect shortens the vehicle's stopping distance once more. The driver can also actively suppress coasting by quickly removing his/her foot from the accelerator pedal (e.g. approaching a bend, aborting a passing attempt). Coasting can also be triggered when specifically desired by the driver by pressing the upshift button in the highest gear (accelerator pedal not pressed). Engagement takes place automatically during acceleration. Prerequisites for coasting mode: Driving in selector-lever position D Coasting mode is switched on (Auto Start Stop not deactivated using switch) Sport or Sport Plus mode is deactivated PSM is active Engine, transmission and battery have reached operating temperature Relaxed/economic driving style Slight uphill or downhill gradient Remove foot slowly from the accelerator pedal Ending coasting mode: Press the accelerator pedal or Press the brake pedal or Change gears using the selector lever Coasting mode can be deactivated using the Auto Start Stop switch. Notes: Page 9.52 Fuel/Ignition Diagnosis & Repair

181 Additional DME Functions & Special Control Systems Vehicle Electrical System Recuperation in Communication With Gateway Control Unit This control operation includes the DME control unit, the gateway control unit, the brake pedal sensor, starter battery with battery sensor, the generator and the vehicle electrical system. Vehicle electrical system recuperation helps to reduce fuel consumption. Some of the kinetic braking energy is converted into electrical energy via the generator during vehicle deceleration phases and is fed into the starter battery. As a result, the combustion engine has to supply less power to charge the battery through generator operation in acceleration phases. Depending on the battery condition, the vehicle voltage is raised and lowered correspondingly and varies between 12.5 and 15.5 V. Porsche vehicles feature the new function of vehicle electrical system recuperation as a further fuel-saving measure. Here, some of the kinetic braking energy can be converted into electrical energy via the generator during vehicle deceleration phases and stored in the starter battery. As a result, the combustion engine has to supply less power to charge the battery through generator operation in acceleration phases in particular, which directly results in lower fuel consumption. The starter battery is preferably charged by the usually otherwise lost braking energy during the braking operation. During braking, the generator output is increased in a targeted manner by the generator regulator and the recuperated energy is fed into the starter battery. The voltage is then lowered again and the energy can be fed into the vehicle electrical system in order to supply the loads. The increased generator power acts with a low braking torque on the crankshaft of the combustion engine via a drive belt. This leads to vehicle deceleration and therefore supports the conventional brake system. A new intelligent algorithm in the energy management system evaluates various input variables of the components involved, thereby allowing active coordination of every recuperation operation based on the battery charge condition and driver request. This control operation includes, among others, the engine control, brake pedal sensor, starter battery with sensor system, generator and the vehicle electrical system. The powerful AGM battery meets all requirements with respect to battery life in view of the increased number of cycles due to frequent charging and discharge. Increase Idle Speed to Increase the Charging Current The idle speed can be increased in three stages after a corresponding request from the gateway. The charging current of the generator is increased as a result. The field current is regulated in the gateway. To increase the generator output, the idle speed can be increased in three stages when the engine is warm (e.g. V8 engines 640, 740 and 850 rpm). Sport Button Allows the driver to choose between a setup with optimized comfort and consumption or a sporty setup. Standard Setting In Normal mode, the electronic engine management system restricts the engine torque in order to optimize fuel consumption (except during kickdown). Optimized comfort and fuel consumption Dynamically comfortable accelerator characteristic Sport Mode When the Sport button is activated, a SPORT symbol lights on the instrument cluster. A sportier vehicle setup is obtained when Sport mode is switched on. Auto Start Stop function deactivated Sporty engine setup Accelerator reacts more quickly, more spontaneous throttle response Throttle open further for same pedal travel Coolant temperature is reduced The electronic engine management system controls the engine with more bite. The dynamic response of the engine then becomes even more direct. On vehicles with 8-speed Tiptronic S, up shifts take place later and downshifts earlier in automatic mode. The Auto Start Stop function is also deactivated. In addition, the chassis control systems Porsche Active Suspension Management (PASM) and the optional Porsche Dynamic Chassis Control (PDCC) if equipped are switched to Sport mode. Fuel/Ignition Diagnosis & Repair Page 9.53

182 Additional DME Functions & Special Control Systems This makes damping sportier and the steering behavior in bends is more direct. This in turn leads to improved road contact. Activation of the Sport button influences the areas DME, Tiptronic S, PTM, PASM and PDCC. Sport Plus Button (Optional Equipment) Communication with Adaptive Cruise Control (ACC) In communication with the control unit of the adaptive cruise control, it is possible to perform acceleration or deceleration via the electronic throttle and where appropriate braking, also to vehicle stop. Auto Start Stop function deactivated For even sportier setup Performance-orientated Turbo with overboost Coolant temperature is lowered Activation of the shift indicator Off-road Mode for Cayenne In off-road mode, the accelerator pedal characteristic is very flat at low speed in order to ensure precise throttle control when driving off-road. At faster speeds, the accelerator pedal characteristic becomes increasingly more responsive for better handling on sand dunes. Notes: Page 9.54 Fuel/Ignition Diagnosis & Repair

183 Systems That Effect Engine Management System Operation Via Data Transfer Additional DME Functions & Special Control Systems There are several systems that have effect on the operation of engine management via programs in the engine management control unit that utilize data from other systems. Tiptronic Transmission Porsche has had the engine management system act on information from the transmission going back to the 928. The 928 has a switch that closes when the transmission shifts from 1st to 2nd so the ignition control can retard the ignition timing to soften the upshift. All Porsche vehicles with Tiptronic and PDK transmissions have communication between the engine management control and transmission control so the transmission and engine can operate in coordination. The data transfer is bi-directional with load, RPM, throttle position, ambient conditions and engine temperature transferred from engine management to transmission control, and requests to retard ignition timing and gear selector position are sent from transmission control to engine management. When the engine is cold, the transmission control engages a catalyst warm up shift program to speed catalyst warm up. This is why the transmission control is OBD-II relevant and why the MIL can be turned on by the transmission control unit. In 1997, the Boxster was the first Porsche vehicle to utilize a CAN bus system. It was used to connect the Tiptronic control unit to the Engine Management Control Unit. Fuel/Ignition Diagnosis & Repair Page 9.55

184 Additional DME Functions & Special Control Systems Stability Management The Carrera (993) was equipped with ABD (automatic brake differential). Porsche traction control began to utilize information from the engine management system. ABD actuates the rear brakes to eliminate wheel slip and it utilizes load information from engine management to determine the limit for brake actuation (when load is high the brake application time limit is shortened). Sport Chrono The Carrera (997), Boxster (987) and 9x1s have Sport Chrono as an option, when this system is active the engine management switches the E-throttle to a faster rise of the throttle opening curve and a more aggressive RPM limiter. Sports Chrono Functions of the Motronic As Porsche stability management has evolved, the interaction between engine management and stability management has become more complex with more data shared between systems and more intervention in engine management by stability management. Traction Control (TC) The 1997 Boxster (986) introduced TC (traction control), this combined ABD and ASC (anti-slip control). When this system detects a poor traction condition, it will limit the amount of torque that the engine produces. The engine management can reduce the amount of fuel injected, and retard the ignition timing to reduce torque to the limit determined by ASC. ASC remains a component of subsequent stability management systems, with E-throttle, the engine management has control of throttle position as well as the timing and fuel metering. This allows E-throttle to control the amount of torque produced very precisely. E-throttle Characteristic Engine Drag Control (EDC) The 911 Carrera 4 (996) in 1999 came equipped with PSM (Porsche Stability Management) with ASC as an element of the system. Another engine management related system component is EDC (Engine Drag Control). When EDC detects the rear wheels braking loose when decelerating with engine braking, it instructs the engine management control to open the throttle to reduce the amount of engine braking produced. Speed Limiter Characteristic Page 9.56 Fuel/Ignition Diagnosis & Repair

185 Conversion Charts Temperature Conversion Metric Conversion Formulas INCH X 25.4 = MM MM X.0394 = INCH MILE X = KILOMETER (KM) KM (KILOMETER)... X.621 = MILE OUNCE X = GRAM GRAM X.0352 = OUNCE POUND (lb)... X.454 = KILOGRAM (kg) kg (KILOGRAM) X = lb (POUND) CUBIC INCH X = CUBIC CENTIMETER (cc) cc (CUBIC CENTIMETER)... X.061 = CUBIC INCH LITERS X.0353 = CUBIC FEET (cu.ft.) CUBIC FEET (cu.ft.) X = LITERS CUBIC METERS..... X = CUBIC FEET (cu.ft.) FOOTPOUND(ft lb)..... X = NEWTON METER (Nm) Nm (NEWTON METER) X.7376 = ft lb (FOOT POUND) HORSEPOWER (SAE)... X.746 = KILOWATT (Kw) HORSEPOWER (DIN)... X.9861 = HORSEPOWER (SAE) Kw (KILOWATT) X 1.34 = HORSEPOWER (SAE) HORSEPOWER (SAE)... X = HORSEPOWER (DIN) MPG (MILES PER GALLON)... X.4251 = Km/l (KILOMETER PER LITER) BAR X 14.5 = POUND/SQ. INCH (PSI) PSI (POUND SQUARE INCH).... X.0689 = BAR GALLON X = LITER LITER X.2642 = GALLON FAHRENHEIT = CELSIUS CELSIUS X = FAHRENHEIT Fuel/Ignition Diagnosis & Repair Page 10.1