beginning of the seventies. Around 1988, this technology also found its way into vehicles with diesel engines. Nowadays, practically all modern

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1 PN_ PIERBURG - page 1/10 Exhaust gas cleaning as a result of exhaust gas recirculation Return to sender Exhaust gas recirculation (EGR) is a reliable and proven method for emission control that is today even more indispensable than ever. Pierburg, the market leader where exhaust gas recirculation is concerned, provide advice on components, causes of failure and remedies. The first EGR systems were used on gasoline/petrol engine at the beginning of the seventies. Around 1988, this technology also found its way into vehicles with diesel engines. Nowadays, practically all modern diesel engines are provided with EGR technology so as to be able to comply with present-day tightened exhaust gas regulations. EGR at a glance Diesel engine (all injection types) Effects Nitrogen oxides -50% Particulates -10% Less hydrocarbons Less noise Return rates Others Gasoline/petrol engine (manifold injection) Nitrogen oxides -40% Consumption -3% Less CO 2 Gasoline/petrol engine (direct injection) Nitrogen oxides % Consumption -2% Less CO 2 max. 50% max. 20% max. 50% (with stratified charge) max. 30% (with homogenous operation) For vehicle with higher weight class EGR cooling required EGR cooling is under discussion Higher EGR rates at high load Fig 1: Principle of exhaust gas recirculation In this case, the actuation of the pneumatic EGR valve is carried out by an electropneumatic pressure transducer (EPW) 1 Air filter 2 EGR valve (here: pneumatic) 3 Electropneumatic pressure transducer (EPW) 3 Catalytic converter

2 PN_ PIERBURG - page 2/10 Why EGR? At the first sight, one may wonder how it is possible to reduce pollutants by means of exhaust gases in the intake air. By adding exhaust gas, however, the oxygen content in the fuel/air mixture is reduced and, as a result, the combustion temperature in the cylinders lowered. Since harmful nitrogen oxides (NOx) are mainly formed at high temperatures, NO x concentrations blown into the environment can be reduced by up to 50%. On diesel engines, the generation of soot particles is additionally lowered by about 10%. To achieve this, exhaust gas recirculation is only connected at defined operating points: On gasoline/petrol engines this is above idling speed up to the upper partial load, on diesel engines up to approx. 3,000 min -1 and mean load. No exhaust gas recirculation is made at full load, though. In addition, exhaust gas recirculation reduces hydrocarbon, particulate and noise emissions on diesel cars, while on petrol-engine cars the CO 2 emissions and the fuel consumption are lowered. This reduction of consumption in the case of gasoline/petrol engines can be explained by the lower charge-exchange losses and improved mixture formation due to the heat supplied with the exhaust gas.

PN_0035 - PIERBURG - page 3/10 Components for Exhaust Gas Recirculation The most important components in exhaust gas recirculation are, of course, the EGR valves, which dispense the amount of exhaust

In many cases, they are directly attached to the exhaust manifold or intake air system, or they are located in a heat-resistant exhaust gas pipe that connects the exhaust manifold and the intake air

They are actuated by an electric switch over valve (EUV) by way of vacuum. On this simply designed system, the EGR valve has only an open-close function. {see Fig.

3 PN_ PIERBURG - page 3/10 Components for Exhaust Gas Recirculation The most important components in exhaust gas recirculation are, of course, the EGR valves, which dispense the amount of exhaust gas to be recirculated. In many cases, they are directly attached to the exhaust manifold or intake air system, or they are located in a heat-resistant exhaust gas pipe that connects the exhaust manifold and the intake air Fig. 2: Electric switch over valve (EUV) A "switch" for pneumatic EGR valves system. Until the middle of nineties, pneumatic EGR valve were mainly used. They are actuated by an electric switch over valve (EUV) by way of vacuum. On this simply designed system, the EGR valve has only an open-close function. {see Fig. 2 and 3} On more modern systems, actuation is carried out by way of an electropneumatic pressure transducer (EPW) which enables the EGR valve to be continuously adjusted. This consequently facilitates rapid and extremely precise adaptations to the relevant operating points. {see Fig. 4} Fig. 3: A selection of EGR valve for gasoline/petrol engines: Left: Electric EGR valve with connection to the coolant circuit Centre: Pneumatic EGR valve Right: Electric EGR valve In recent years, there has been a continuous change from the pneumatic over electromagnetic to electromotive control of the EGR valve. These eegr valves no longer need a vacuum or a solenoid valve for actuating purposes and enable an even faster adaptation of the operating point to the engine-related requirements. Fig. 4: Electropneumatic pressure transducer (EPW)

$PN_0035 - PIERBURG - page 4/10 Electric EGR valves are directly actuated by the control unit. {see Fig. 5} Some EGR valves are equipped with potentiometers for position feedback.$ Since high temperatures can cause malfunctions on electric EGR valves, they are connected to the coolant circuit for certain applications.

Since high temperatures can cause malfunctions on electric EGR valves, they are connected to the coolant circuit for certain applications.

5: Some EGR valves for diesel engines: EGR valves for diesel applications have large opening widths to allow for the high return rates.

4 PN_ PIERBURG - page 4/10 Electric EGR valves are directly actuated by the control unit. {see Fig. 5} Some EGR valves are equipped with potentiometers for position feedback. This position feedback enables both an opening correction and permanent monitoring. Other EGR valves are additionally provided with incorporated temperature feelers for monitoring purposes. Since high temperatures can cause malfunctions on electric EGR valves, they are connected to the coolant circuit for certain applications. Exhaust gas recirculation on diesel vehicles requires high exhaust gas Fig. 5: Some EGR valves for diesel engines: EGR valves for diesel applications have large opening widths to allow for the high return rates. These opening widths are considerably smaller on gasoline/petrol engines. recirculation rates of up to 60% for which the pressure difference between exhaust side and intake side is inadequate on its own. For this reason, "regulating throttles" are used to enhance the vacuum in the intake manifold, enabling the increase and the exact regulation of the exhaust gas recirculation rates. Other common designations are "Diesel throttles" or "Diesel prethrottles". {see Fig. 6} Another important component for exhaust gas recirculation is the air mass sensor. Its signal is - among other things - used on diesel engines for regulating Fig. 6: Diesel regulating throttle (EDR- Di) the exhaust gas recirculation. {see Fig. 5 and 7} Fig. 7: Various air mass sensors designs

5 PN_ PIERBURG - page 5/10 Outlooks In view of the increasingly stringent stipulation in the legislation governing exhaust gases, vehicles are being equipped with EGR coolers to an even greater extent. In the first place, the cooler exhaust gas prevents fresh air from being heated up as a result, the amount of nitrogen oxides, which are formed predominantly at high combustion temperatures, are considerably reduced. Secondly, cooler gases, whether air or exhaust gas, are denser, i.e. a cylinder filling can take up a higher mass at the same boost pressure. In addition, the resulting enleanment has positive effects on fuel consumption and particulate emissions. Exhaust gas recirculation cannot only occur "externally". By using the method called "internal" or "interior" exhaust gas recirculation the opening times of intake and exhaust valves overlap. A residual amount of exhaust gas consequently remains in the cylinder and mixes with the new air streaming in. This "valve overlapping" effect only becomes possible as a result of variable or electromagnetic valve control systems. Since, however, the valve control system must primarily provide optimum combustion and power; the internal EGR will remain only a supplement for the "classical" exhaust gas recirculation, even in the future.

PN_0035 - PIERBURG - page 6/10 EGR and OBD In times before vehicles were equipped with component monitoring systems, the failure of a component in the EGR system often remained almost unnoticed.

6 PN_ PIERBURG - page 6/10 EGR and OBD In times before vehicles were equipped with component monitoring systems, the failure of a component in the EGR system often remained almost unnoticed. However, since the introduction of on-board diagnostic systems known as "OBD" every malfunction is "a case for the repair shop". Within the scope of OBD II (USA), the EGR system is monitored for function and effect. Acc. to EOBD, the European version, electric monitoring of the components and monitoring the function are adequate. EOBD does not stipulate any test of the effectiveness. Various manufacturers also supply EC vehicles acc. to OBD II standards. However, one observation is of extreme importance when troubleshooting: Although EGR components are monitored by on-board diagnostic system i.e. a failure or incorrect functioning will be detected; this is not always the actual cause of the failure or the fault. One of the most frequent causes of malfunctions in the EGR system is stuck or carbonised EGR valves that becomes noticeable, for instance, through error messages such as "flow rate too high" or "too low". {see Fig. 8} However, since nothing "gets stuck" by itself, the actual causes must be investigated. And these can be of various kinds. Fig 7: Since EGR valves cannot get clogged by themselves, the causes must be investigated.

7 PN_ PIERBURG - page 7/10 Disturbed Behaviour The recirculated exhaust gas contains both gaseous pollutants and soot particles, in particular on diesel-engine vehicles. If then oil is added to the intake air, cases of carbon-fouling or sticking can occur which, at some point, the force of the valve can no longer cope with the EGR valve cannot be opened or remains in its open state. The consequences are jerking, irregular idling or lack of power. There may be various causes for an intensely oily intake or charge air. These range from malfunctions in the crankcase ventilation, worn-out bearings or a plugged oil return line on the turbocharger, to worn-out valve stem seals or valve guides. But also ordinary cause such as incorrect oil change or oil filter replacement, use of engine oil grades that are unsuitable for the application or an excessive engine oil level may result in the EGR valve sticking. Unusually thick deposits can also be caused by faults in the injection system. Although EGR valves are designed for the high temperatures that occur in the exhaust branch, the valve may occasionally have thermal damage. The causes may be incorrect actuation, too high exhaust gas back pressure or a non-opening blow-off valve ("wastegate valve") of the turbocharger. It may even be a matter of deliberate manipulation to increase the boost pressure.

PN_0035 - PIERBURG - page 8/10 There are even some individuals who are not afraid of shutting down the EGR system completely.

8 PN_ PIERBURG - page 8/10 There are even some individuals who are not afraid of shutting down the EGR system completely. But apart the fact that the operating licence (ABE) then expires, this shutting down may also result in a knocking combustion and, consequently, in severe engine damage. A relatively new form of claims on EGR valves are complaints such as "New part without function". If a new EGR is installed after a failure and the vehicle behaves as if the valve had not been replaced, at all, the engine control unit must first "get to know" the new valve. {see Fig. 9} Modern engine control units are equipped with "adaptive storage modules", i.e. map data required for operations must be "learned". This is done either during a longer trial drive or by using a specific program option of the engine tester, e.g. "basic setting". The function of pneumatically controlled EGR valves can easily be tested Fig. 9: Whether pneumatic EGR valves or electropneumatic pressure transducer: These components can easily be tested by using a vacuum hand pump using a vacuum hand pump. Electric EGR valves can mostly be actuated by way of an actuator diagnosis via the engine tester. In both cases, switching properly functioning valves can be heard as a slight "clicking" sound when the engine is at a standstill. These and other testing options are described in detail in Pierburg Service Information SI 0038 (for gasoline/petrol engines) and in SI 0039 (for diesel engines).

9 PN_ PIERBURG - page 9/10 Especially with pneumatic EGR valves, a potential cause of malfunctions can be found throughout the vacuum control sector. This includes the vacuum pump, vacuum lines and the solenoid valves to be controlled, as the electric switch over valve (EUV), or the electropneumatic pressure transducer (EPW). The Service Information publications mentioned above also include test options on this topic. An example of an incorrect allocation of fault was shown, for instance, on an Opel 1.7 XDT engine. Acc. to the scan tool, the error diagnosis was "exhaust gas recirculation rate too low". Subsequent to inspecting the EGR valve and the electropneumatic pressure transducer to be actuated, the air mass sensor turned out to be the actual fault-inducing component. Since the air mass sensor is an essential component for controlling the exhaust gas recirculation on diesel engines, it is also a potential source for malfunctions. In the event of leaks in the intake air system, dirt particles can enter with the intake air, hitting the air mass sensor at high speed and destroying the sensitive sensor element. Excessive oil mist from the crankcase ventilation or oil-wetted sports air filters can lead to an oil-clogged sensor.

PN_0035 - PIERBURG - page 10/10 Splash water, e.g. during heavy rain, can reach the clean air side via the air filter and damage or foul the sensor. Salt water, e.g. from road salt and sleet enhances this effect.

10} So, if there are any problems with exhaust gas recirculation just "think outside the box" and view the system as a whole.

10 PN_ PIERBURG - page 10/10 Splash water, e.g. during heavy rain, can reach the clean air side via the air filter and damage or foul the sensor. Salt water, e.g. from road salt and sleet enhances this effect. In particular on diesel engines, where the air flow is considerably higher than in gasoline/petrol engines, the air mass sensor may then be subjected to a downright "particulate fire". {see Fig. 10} So, if there are any problems with exhaust gas recirculation just "think outside the box" and view the system as a whole. The OBD system often captures only the symptoms the causes need to be detected by the Fig. 10: A "pickled" air mass sensor under the microscope: Salt and dirt may damage the sensor the least they do is falsify the measurements expert. (MSI) is the sales organisation for the worldwide aftermarket activities of Kolbenschmidt Pierburg AG. We are a leading supplier of engine components for the independent aftermarket, featuring the premium brands KOLBENSCHMIDT, PIERBURG and TRW Engine Components. The MSI product range is both broad and deep, enabling customers to procure all engine components from one source. As a problem solver in the marketplace and the workshop, MSI offers extensive services and the technical expertise that you would expect from the subsidiary of one the largest automotive suppliers. To request special projects; information and visual material please use the following contacts: For PIERBURG subjects Dieter Bohn Phone: Mail: dieter.bohn@de.kspg.com For KOLBENSCHMIDT / Simon Schnaibel Phone: TRW Engine Components subjects Mail: simon.schnaibel@de.kspg.com

Emission control and OBD

Emission control and OBD Our knowledge for your work SERVICE TIPS & INFOS POSTER INSIDE OBD = On-Board Diagnostic System The European on-board diagnostic system (EOBD) is still virgin territory to many