Electronic Engine Controls (With Supercharger): Overview Jaguar XKR II

OVERVIEW

The V8 supercharged engine is controlled by an ECM. The Engine Management System (EMS) controls the following

1. Engine fueling
2. Ignition timing
3. Closed loop fueling
4. Knock control
5. Idle speed control
6. Emission control
7. On Board Diagnostic (OBD)
8. Interface with the immobilization system
9. Speed control

The ECM controls the engine fueling by providing sequential fuel injection to all cylinders. Ignition is controlled by a direct ignition system, provided by eight plug top coils. The ECM is able to detect and correct for ignition knock on each cylinder and adjust the ignition timing for each cylinder to achieve optimum performance.

The ECM uses a torque-based strategy to generate the torque required by the driver and other vehicle control modules. The EMS uses various sensors to determine the torque required from the engine. The EMS also interfaces with other vehicle electronic control modules's, via the CAN bus, to obtain additional information (e.g. road speed from the ABS control module). The EMS processes these signals and decides how much torque to generate. Torque is then generated by using various actuators to supply air, fuel and spark to the engine (electronic throttle, injectors, coils, etc.).

Scheme 3

The ECM and bracket assembly are attached to the vehicle on the left hand side in the secondary bulkhead area using 3 m6 nuts, 2 off onto the longitudinal and 1 off to the wheel arch apron panel.

System ECM has the following inputs

1. RCM
2. Park/neutral switch
3. Ignition coil feedback x8
4. Fuel rail temperature
5. Fuel rail pressure
6. Supercharger inlet pressure
7. Mass air flow
8. Engine speed
9. Camshaft position x2
10. Driver demand
11. Brake pedal position switch
12. Speed control switches
13. Generator load
14. Oxygen sensors pre catalyst x2
15. Oxygen sensors post catalyst x2
16. Throttle position
17. Cooling fan speed
18. Ignition switch position
19. Knock sensors x2
20. Manifold Absolute pressure (MAP)
21. Intercooler temperature
22. Coolant temperature
23. Engine oil temperature

The ECM outputs to the following

1. Electric throttle Actuator
2. Brake vacuum pump relay
3. Ignition coils (x8)
4. Oxygen sensor heaters (4)
5. Fuel injectors (8)
6. Purge Valve
7. Engine Cooling Fan
8. Fuel pump relay
9. Starter Relay
10. EMS Main Relay
11. Electric Fan Control
12. Generator Control
13. Fuel tank leakage monitoring (NAS Only)
14. Fuel Pump Driver Module (FPDM)

Scheme 4

The crankshaft position sensor is mounted at the rear underside of the engine near the transmission bell housing. Connection between the sensor and the harness is via a link harness and a two-way connector. Both wires go directly to the ECM. The sensor produces the signal which enables the ECM to determine the angle of the crankshaft, and the engine RPM. From this, the point of ignition, fuel injection, etc. is calculated. If the signal wires are reversed a 3 degrees advance in timing will occur, as the electronics within the ECM uses the falling edge of the signal waveform as its reference/timing point for each tooth.

The reluctor is pressed into the flywheel and has a "tooth" pattern based on 36 teeth at 10° intervals and approximately 5° wide: one of the teeth is removed to provide a hardware reference mark which is 30 degrees BTDC No.1 cylinder. Because of the crankshaft sensor's orientation, the target wheel uses windows stamped into the face, rather than actual teeth.

The sensor operates by generating an output voltage caused by the change in magnetic field that occurs as the windows pass in front of the sensor. The output voltage varies with the speed of the windows passing the sensor, the higher the engine speed, the higher the output voltage. Note that the output is also dependent on the air gap between the sensor and the teeth (the larger the gap, the weaker the signal, the lower the output voltage). The ECM transmits the engine speed to other vehicle control modules on CAN.

Scheme 5

Two sensors are located at the rear of the engine, in the cylinder head (one per bank), above the rear cylinders. The sensors are Variable Reluctor Sensor (VRS) type, producing four pulses for every two engine crankshaft revolutions. The sensing element is positioned between 0 and 2mm from the side of the cam gear wheel.

The camshaft timing wheel is a centered component which has four teeth on it to enable the EMS to detect cylinder identification. The signal is used for

1. Cylinder recognition
2. Enabling sequential fuel injection
3. Knock control
4. Cylinder identification for diagnostic purposes.

Failure symptoms include

1. Ignition timing reverting to the base mapping, with no cylinder correction.
2. Active knock control is disabled, along with its diagnostic (Safe ignition map - loss of performance).
3. Quick cam/crank synchronization on start disabled.

Scheme 6

Oil temperature is monitored through a temperature sensor mounted in the oil system. This component is a NTC. The sensor is mounted next to the oil pressure sensor at the front of the engine and locates into the oil filter bracket.

Scheme 7

The fuel rail temperature sensor measures the temperature of the fuel in the fuel rail. This input is then used to deliver the correct quantity of fuel to the engine. The sensors operating range is -40 Degrees Celsius to 150 Degrees Celsius. The fuel rail temperature sensor is fitted on the rear of the right hand bank fuel rail.

Scheme 8

The fuel rail pressure sensor is located on top of the fuel rail adjacent to the fuel inlet. The fuel rail pressure sensor measures the pressure of the fuel in the fuel rail. This input is then used by the fuel pump control module to control the amount of fuel delivered to the fuel rail.

Scheme 9

The fuel tank leakage monitoring system periodically checks the evaporative system and the fuel tank for leaks when the ignition is switched off. The fuel tank leakage monitoring pump is connected to the atmospheric vent of the charcoal canister and incorporates a PTC heating element a normally open valve and a reference orifice. The fuel tank leakage monitoring pump is only operated when the ignition is switched off and is controlled by the ECM. The ECM also monitors the electric air pump operation and the normally open valve for faults. To check the fuel tank and EVAP system for leaks the ECM operates the fuel tank leakage monitoring pump and monitors the current draw. This is compared to a referenced figure established from the current draw when air is pumped through the reference orifice. Refer to Evaporative Emissions - Vehicles With: Supercharger article.

Scheme 10

The purge valve is located on the LH side of the engine on a bracket which is attached to the cylinder head. The purge valve is a solenoid operated valve which is closed when de-energized. The purge valve is controlled by a 10Hz PWM signal from the ECM. When the engine operating conditions are correct, the ECM opens the purge valve which causes fuel vapor and fresh air to be drawn through the charcoal canister. The fresh air is drawn through the charcoal canister via the fuel tank leakage monitoring pump fresh air vent. Refer to Evaporative Emissions - Vehicles With: Supercharger article.

Scheme 11

Two MAF/IAT sensors are located in the clean air duct immediately after the air cleaner box.

The air mass flow is determined by the cooling effect of inlet air passing over a "hot film" element contained within the device. The higher the air flow the greater the cooling effect and the lower the electrical resistance of the "hot film" element. The ECM then uses this signal from the MAF to calculate the air mass flowing into the engine.

The measured air mass flow is used in determining the fuel quantity to be injected in order to maintain the stoichiometric air/fuel mixture required for correct operation of the engine and exhaust catalysts. Should the device fail there is a software backup strategy that will be evoked once a fault has been diagnosed.

The following symptoms may be observed if the sensor fails

1. During driving the engine RPM might dip, before recovering.
2. Difficulty in starting or start - stall.
3. Poor throttle response/engine performance.
4. Lambda control and idle speed control halted.
5. Emissions incorrect.
6. AFM signal offset

The sensor is integrated into the MAF meter. It is a temperature dependent resistor (thermistor), i.e. the resistance of the sensor varies with temperature. This thermistor is a NTC type element meaning that the sensor resistance decreases as the sensor temperature increases. The sensor forms part of a voltage divider chain with an additional resistor in the ECM. The voltage from this sensor changes as the sensor resistance changes, thus relating the air temperature to the voltage measured by the ECM.

The ECM stores a 25 Degrees Celsius default value for air temperature in the event of a sensor failure.

Scheme 12

The MAP sensor is located in the LH side of the throttle elbow.

The MAP sensor provides a voltage proportional to the absolute pressure in the supercharger intake. This signal allows the load on the engine to be calculated and used within the internal calculations of the MAP. The sensor is located below the electric throttle on the induction elbow.

The output signal from the MAP sensor, together with the CKP and IAT sensors, is used by the ECM to calculate the amount of air induced into the cylinders. This enables the ECM to determine ignition timing and fuel injection duration values.

If the MAP signal is missing, the ECM will substitute a default manifold pressure reading based on crankshaft speed and throttle angle. The engine will continue to run with reduced driveability and increased emissions, although this may not be immediately apparent to the driver. The ECM will store fault codes which can be retrieved using Land Rover recommended diagnostic tool.

Principle of Operation

For a detailed description of electronic engine controls, refer to the relevant Description and Operation article. See Electronic Engine Controls .