Pilot Fuel Injection (Engine management system - EDC)

l Engine coolant temperature: This information is used, in conjunction with the CKP and the fuelling map, to set the injection quantity to the correct value. l Injector rail pressure: This information is used during fuelling calculations to correct the electrical opening times (injector duty cycle) to compensate for variations in fuel pressure. l Mass air flow: This information is used by the ECM to calculate the mass of air which has entered the cylinders, and hence the amount of oxygen available for combustion of the fuel. It also allows the ECM to monitor EGR flow when the system is active. l Intake air temperature: This information is required by the ECM to provide a correction factor for differing intake air temperatures. Cold air contains more oxygen than hot air for any given volume, therefore the fuelling must be adjusted to suit the prevailing conditions. l Accelerator pedal position: This information is vital to the operation of the ECM and the vehicle. The ECM interprets the electrical signal from the throttle potentiometer as 'throttle' demand and controls the power output of the engine accordingly.

Pilot Fuel Injection

Pilot fuel injection helps to reduce engine clatter and vibration. The ECM provides this feature by opening the electronic fuel injectors briefly before injecting the main charge of fuel. This makes the flame front propagation through the main charge less abrupt, giving reduced levels of diesel knock.

Smoke Limitation

This requires high injection pressure to improve the atomisation of the fuel injected into the cylinders. By maintaining high fuel pressures at low engine speeds the ECM maximises the atomisation of the fuel for conditions where turbulence in the combustion chamber is reduced. The strategy contained in the ECM does not allow more fuel to be injected than there is oxygen available in the cylinders.

Active Surge Damping

Active surge damping is implemented to prevent the engine surging when the EAT ECU changes gear, or the clutch switch indicates that the clutch pedal is depressed. The ECM will reduce fuelling to lower the engine torque output, thereby preventing engine surge.

Variable Nozzle Turbine

The variable nozzle turbine makes it possible to vary the exhaust gas flow of the turbine by varying the angle that the guide vanes are set at. With the guide vanes in a closed position the exhaust gas flow is reduced and the gas flow to the turbine wheel is increased. This results in an increase in boost pressure.

The boost pressure sensor provides a feed back a signal relative to inlet manifold pressure to the ECM. The ECM also calculates engine load and uses this along with the boost pressure sensor input to send a signal (PWM) to the vacuum control module to determine the amount of vacuum supplied to the vacuum control cell. The amount of vacuum operates between 0 mBar to 640 mBar depression (640 mBar with the vanes fully closed-maximum boost).

Air Conditioning (A/C)

The A/C system is dependent on the ECM for actuation of the compressor clutch. While the engine is running, the ECM receives a compressor on/off request on the CAN bus every 10 seconds, and each time that the A/C is turned on or off. When the request is for the compressor to be turned on, the ECM will engage the compressor clutch providing the following conditions exist: l All engine sensors are functioning. l The engine is not under heavy load (i.e. accelerator pedal is not fully down). l The coolant temperature is not more than 118 °C (244 °F). l Evaporator temperature not less than -7 °C (25 °F). l Engine speed over 500 rev/min. l A/C refrigerant pressure within the limits required by the trinary switch.

The ECM engages the compressor clutch by providing an earth path for the A/C compressor clutch relay winding. The contacts in the relay close and supply a 12 volt feed to engage the compressor clutch. When the compressor clutch request has been granted a confirmation message is broadcast on the CAN bus.

If any of the conditions necessary to engage the compressor clutch cease to exist, the ECM will disengage the compressor. The ECM broadcasts a confirmation that the A/C clutch has been disengaged on the CAN bus.