Fuel Injection

As the engine is turned by the starter motor, the engine speed (RPM) engine speed sensor (7/25) and camshaft position (CMP) sensor (7/21) provide the engine control module with engine speed and crankshaft position signals. The engine control module opens injectors (8/6 - 8/11) once per working cycle to inject fuel.

One injector terminal is connected to 12 V from the main relay, while a second terminal is connected to the engine control module. The engine control module activates the injectors by grounding their cables.

During the start-up phase, the engine control module computes the injection period on the basis of engine temperature and speed signals.

When the engine is running, the injection period is based on engine speed, temperature and load, battery voltage, and other parameters.

The engine control module opens the injectors individually in what is known as sequential fuel injection (SFI), enabling the fuel to be injected at the optimum instant to achieve a homogeneous air/fuel mixture. Under normal running conditions, injection commences immediately before the injector opens.

When the heated oxygen sensor (HO2S) (7/15) has reached working temperature, its signal is also used to compute injected fuel quantity.

The engine control module compensates for variations in battery voltage, acceleration and load. The engine control module also controls fuel shut-off during engine braking. The system also incorporates adaptive functions, which store information about optimum fuel injection under different running conditions. The engine control module uses this information to compensate for component wear and tolerances. This minimizes exhaust gas emission levels, maintenance and adjustments.

If the engine is knocking and the knock is not eliminated by retarding the ignition, additional fuel is injected to reduce the temperature of the combustion process.

The engine control module interrupts fuel injection if the speed of the car reaches 250 km/h (155 mph) or the engine speed reaches a maximum of 6,200 rpm and under engine braking conditions.

If the engine is over-revved, the engine control module will cut off the fuel supply to prevent damage. The engine speed may be 6,500 rpm for 2.5 seconds, after that the limit is lowered to 6,200 rpm.

The fuel supply is interrupted during engine braking if engine speed is above 1,800 rpm (1,920 rpm in cars with automatic transmission), the throttle is closed (idling) and the engine coolant temperature (ECT) has reached a specific value. When engine speed drops below 1,200-1,800 rpm (1,200-1,920 rpm in cars with automatic transmission) fuel injection is resumed.