Supermarine Aircraft GM Isuzu V6 Engine

Transcription

1 Supermarine Aircraft GM Isuzu V6 Engine General over view, aim, reasoning, details and specifications. Testing and analysis with pictures and graphical representatons. Geoff Braddock 26/02/2006 Version One

2 Supermarine Aircraft GM Isuzu V6 Engine Overview Due to the nature of the MK26 Spitfire, it was always envisaged that a V configuration engine would one day be offered. There are any number of V8 engine kits available but all are too heavy and did not fit within the original design criteria, that of a light responsive and forgiving aircraft with universal appeal as evidenced by market research and feedback. Although V8 powered aircraft were talked about, the reality is that most pilots were looking for an aircraft as outlined in our criteria. The V6 eventually chosen is an all alloy belt driven, quad cam V6 with 4 valves per cylinder. This engine is manufactured by Honda Japan under licence for Isuzu and is used in 10's of thousands of vehicles world wide. From our research the reliability of this engine is extremely good and investigation with the vehicle manufacturers using this engine has confirmed this reliability record. Aim Provide a light, powerful, well engineered, reliable and cost effective automotive derived firewall forward engine package with PSRU, looms, cooling system and all associated hardware suitable for installation in MK26 Spitfire and other kit built aircraft. This package is designed to be installed by the average builder without the need for specialised training, knowledge or tooling and to be maintained with the same view. Reasoning Modern aircraft piston engines are for the most part very well engineered, reliable units. However they are very expensive to run and maintain and require the services of specialists to install and maintain them. This does not fit within the design criteria of the MK26 Spitfire. The automotive derived engines available are extremely reliable,cheap and technologically advanced with good specific power output and easily maintained. The V6 engine chosen for the MK26 Spitfire falls well within this criteria and that of the overall criteria as relates to the MK26.

3 Engines The engine chosen is an all alloy V6 with belt driven overhead cams with non interferance cam timing. They have direct cam over shim on bucket valve actuation and 4 valves per cylinder. The fuel and ignition is controlled sequentially by a state of the art aftermarket computer management system. The engine is naturally aspirated through a single throttle body mounted to the front of the intake manifold with cast equal length intake runners. Lubrication is by wet sump high pressure internal oil pump with full pressure feed to all bearing journals. A full flow oil cooler is incorporated into the system with a remotely mounted large capacity oil filter with commonly available screw on filter elements. The engine is internally balanced ex factory. A high output automotive style alternator is used and driven by a multi V belt off the front of the engine. Cooling system is standard automotive, thermostatically controlled using a 50/50 water inhibitor mix. The coolant pump is driven by the cam belt. The coolant radiator is located below and to the rear of the engine compartment with cooling air ducted via an intake located at the top front of the engine cowl and exhausted via a cockpit controlled cowling below the radiator. This cooling system has proven to be extremely effective and efficient with a good margin of safety even in hot Australian conditions.

4 Fuel injection and ignition system The fuel injection and ignition are controlled by a fully programable state of the art MoTeC engine management system. The ignition and injection is sequentially operated, meaning fuel and spark are only supplied when required. This method of operation has several advantages over the more common group fired management systems: (1) Increased engine torque and power (2) Decreased fuel consumption. (3) Decreased load on the electrical system. (4) Less waste fuel in manifold and therefore decreased fire risk. (5) Ability to programme redundancy into system because of the individual drivers within the management computer. (6) Elimination of unnecessary systems on motor The spark plugs are fired by individual high output coils, totally eliminating distributors, magnetos and high tension leads. This enables the computer to drive the coils individually and be programmed to allow for redundancy. The engine has been tested with 2 cylinders disabled and returned output figures of 140 hp and 160 lbs/ft torque. See attached dyno chart Fig (1). A single programable MoTeC computer is used. Originally two computers were going to be used but after consultation with the manufacturer it was decided to use one computer as most engine management malfunctions are caused by sensor failure not computer failure. The engine management is comprised of the following: Computer - Primary sensors - Secondary sensors - Redundant maps. All fuel injected motors require input from primary sensors to establish start and finish sequencing. This system has input from two primary sources, ignition trigger and cam angle sensor. Secondary sources comprise of throttle position sensor(tps) Manifold

5 (Fig 1) Dyno printout. 4 cylinders

6 absolute pressure (MAP), Air temperature sensor (ATS) coolant sensor, oil pressure, RPM, fuel pressure. The ignition and cam sensors being the primary sensors are duplicated and a reliable method of switching between the pairs of sensors has been incorporated into the management system. This is controlled from the cockpit and operated in the same way as switching between conventional ignition systems. There is however no decrease in engine rpm when doing mag checks as the computer is only being told to read the second set of primary inputs. Typically there will be an audible blip when doing pre flight engine checks when switching between A and B circuits.the engine will function normally on either A or B circuits. All other functions are considered secondary. For example, if the TPS malfunctions the computer will read from preset stored maps and MAP sensor augmented by input from the remaining functioning sensors. Altitude operation is taken care of by the MAP sensor (Manifold absolute pressure). As altitude increases, air density decreases hence a drop in manifold pressure and therefore a lessening demand for fuel. The computer will automatically lean(trim) the fuel and will also compensate for lower intake air temperature at altitude. Conversely if there is an increase in manifold pressure,ie forced induction or ram induction the computer will increase the fuel required (trim) to compensate. Air temp, ignition retard and advance will also see trimming as a function of engine load. The computer has built in self diagnostic functions and the pilot is alerted to any sesor fault or malfunction via an extremely bright LED mounted in the cockpit. If the malfunction is not corrected by switching from A to B circuit then it is a secondary sensor malfunction and the cockpit gauges should be closely monitored to give an indication of the problem and landing the aircraft is recommended as soon as possible. If the optional MoTeC data dash is installed it will tell the pilot the nature of the malfunction and they can then decide whether or not to land. The system will function on battery or alternator power in the event one or the other fails. An auxiliary power source can be fitted by the builder if they so wish. Consult the factory re this however. Ignition triggers Cam angle sensor MAP sensor TP Sensor AT sensor Coolant temp sensor Oil pressure sensor Fuel pressure sensor

7 Fuel System The fuel system comprises paired high pressure fuel pumps delivering fuel to the fuel rail via a manifold compensated fuel pressure regulator. The system is of the full flow type with regulated fuel pypassed back to the fuel tank. The pumps are manually operated from the cockpit, both being on for take off and only one necessary for the engine requirements at cruise. ( One pump is sufficient for engine demand even at full throttle take off power) The normal procedure is both pumps on for take off or landing. Fuel pressure regulator Fuel pumps Propellor Speed Reduction Unit ( PSRU) The PSRU was designed in house specifically for use with the Isuzu V6 engine and to fit within the already mentioned criteria for the MK26. It consists of a robust aluminium casting housing the prop drive shaft and bearing carrier, top and bottom drive pulleys and crank pulley nose bearing. The use of a toothed aramid fibre and rubber belt dampens out torsional and shock loads transmitted from the prop and the mounting of the cage to the engine mount via integral cast lugs ensures torque, thrust and gyroscopic loads are transmitted mainly to the engine mount and not through the engine crankcases. Prop shaft bearings and bottom crank steady bearing run in a self contained oil system.

8 The toothed drive belt is of arimid fibre and polymer rubber construction and rated to 320 hp and tested continuously at 380 hp for 1000 hours for military use. The prop reduction ratio is 1.755:1. Engine testing The engine has been tested on various load dynos to establish its power and torque characteristics and to map the engine management computer. Hundreds of hours have been spent in dyno testing from which has been gained a broad picture of the engines capabilities, reliablity particular attention being focussed around the rpm area as this is where the engines normal operating range is set. Dyno testing has also been done to establish the engine characteristics under abnormal operating conditions (see fig 1 dyno sheet) with cylinders disabled, sensors disabled etc. It has been established that the motor will run with only one primary sensor functioning (Crank angle sensor) and 2 cylinders disabled,all other sensors disabled and motor running on maps. This is a very unlikely scenario under normal circumstances with the most likely scenario being a sensor malfunction or injector or sparkplug coil malfunction. No malfunction of any sort has been encountered in the course of normal dyno testing. The mapping of the computer has been done on two dirrerent types of dyno, an engine dyno and a rolling road dyno. The computer as mapped has been flown extensively in our test aircraft and has needed no adjustments. All flights to date have been data logged and an extensive amount of information is on hand regarding the engines operation in all flight regimes including positive G aerobatics. Because the engine is wet sump lubricated negative G manouvres are not permitted. To date (26/02/2006 was the most recent flight of our test aircraft) no malfunctions of any sort have been experienced or recorded in flight. See Dyno sheets for typical data recorded during dyno runs. Fig 1 and 2 See MoTeC data logging print outs for typical data recorded during course of flights. Vibration Testing During the course of engine testing a series of dyno and in flight viabration tests were conducted to establish if there were any No Go operational areas for this engine package. A Vibrex 2000 plus spectral viabration analyser was used and a typical spectral analysis graph can be seen at Fig 5. There were no vibration problems recorded in either dyno testing or flight testing especially in the areas of normal operation rpm. Wiring Looms Particular attention has been paid to the manufacture of engine and fuselage looms with both being manufactured in MIL spec wiring and raychem covered. All terminals are of the positive click and lock style with the major firewall plug being a military style bayonet lock type. (see Fig 6). All looms are triple tested before being sealed and then tested on the engine stand in conjunction with the engine testing of the motors pror to packing and shipping. No engines leave the factory without being tested. (See Fig 7)

9 Fig 4

10 Fig 1

11 Fig 2

12 Fig 5 Typical spectral analysis graph for 3000 rpm. (Note decreasing viabration orders with rpm) Fig 6 Bayonet firewall plug Fig 7 Engine run prior to packing and shipping

13 Anciliary items All engines are purchased brand new in their crates and all automotive hardware is removed. This is all replaced with purpose made mounting hardware and looms. All hosing is replaced with high quality 20 year reinforced silicon hose. All necessary sensors are fitted, fuel rails replaced with Billet aluminium rails and high pressure screw on hose fittings are used. Where possible all plastic fittings are replaced with brass or steel and any interference push in type fittings replaced with screw in fittings. Any hose clamps used are stainless steel with rolled edges. Coolant and oil radiators are made from aluminium specifically to our designs. Exhaust system is manufactured in stainless steel Billet alloy fuel rails and steel fittings Bronze fittings and silicon hose High quality Oil line fittings Silicon hose at water header with rolled edge stainless clamps Exhaust system

14 Technical specifications 3.5 litre fuel injected V6 with belt driven overhead cams operating 4 valves per cylinder by direct cam over shim buckets. Cam train is of non interference design. 8.6:1 compression ratio Cast in cylinder block liners with water cooling Bore and stroke: 93.4mm x 85.0mm Valve clearance(cold) Intake.28mm Exhaust.30mm Oil capacity: 5.3 litres (Engine only). Use SAE 0w-40 Full synthetic oil. Performance Data See dyno charts Figs 1 and 2. Max Hp 5200 rpm Max Torque rpm Max engine speed 5500 rpm Max take off (full throttle) manifold Cruise (75% throttle) manifold Idle speed rpm Service information (recommended until further notice) Engine TBO 1500 hrs Spark plug change 100 hrs Tappet adjustment check. 200 hrs (Adjust if necessary) Engine oil change. 25 hrs initial run in, then 50 hrs normal operation or 6 months. Oil filter change. 25 hrs initial run in, then 50 hrs normal operation or 6 months. Fuel filter change (injection) 50 hrs normal operation or 6 months Fuel filter change (in line) 25 hrs normal operation or 3 months Coolant change 100 hrs PSRU oil change. 25 hrs initial run in, then 100 hrs normal operation Cam belt change 500 hrs PSRU belt change 500 hrs Alternator belt change 200 hrs