Fuel Control

FUEL CONTROL
The Powertrain Control Module (PCM) controls the air/fuel ratio of the engine by varying fuel injector ON time. Mass air flow is calculated using the speed density method using engine speed, manifold absolute pressure, and air charge temperature.

Different fuel calculation strategies are used dependent on the operational state of the engine. During crank mode, a prime shot fuel pulse is delivered followed by fuel pulses determined by a crank time strategy. Cold engine operation is determined via an open loop strategy until the O2 sensors have reached operating temperature. At this point, the strategy enters a closed loop mode where fuel requirements are based upon the state of the O2 sensors, engine speed, MAP, throttle position, air temperature, battery voltage, and coolant temperature.

Additional factors can influence fuel pulse width. Asynchronous acceleration enrichment is a technique whereby the duration of injector ON time can be increased for injectors already firing, providing improved acceleration response.

The D3 microcomputer controls fuel injector timing in response to high level commands from the Z2 microcomputer. Injector timing with respect to engine position is determined by the D3 and is transparent to the Z2.