Powertrain Management: Description and Operation

MFI CONTROL

GENERAL INFORMATION
The MFI consists of ECM, which controls the system by receiving the signal from the sensor, detects engine, and the actuator which operates under the control of ECM. The ECM carries out the activities such as fuel injection control, idle air control and ignition timing control.

In addition, the ECM is equipped with several diagnostic test modes which simplify troubleshooting when a problem develops.

FUEL INJECTION CONTROL
Injector drive time and injector timing is controlled so that always an optimum air/fuel mixture is supplied to the engine to correspond to the continually changing engine operation conditions.

A single injector is mounted at the intake port of each cylinder.

Fuel is sent under pressure from the fuel tank by the fuel pump with the pressure being regulated by the fuel pressure regulator. The fuel thus regulated is distributed to each of the injectors.

Fuel injection is normally carried out once for each cylinder for every two rotations of the crankshaft. The firing order is 1-2-3-4-5-6.

The ECM provides a good air/fuel mixture by carrying out "open-loop" control when the engine is cold or operating under high load conditions in order to maintain engine performance. In addition, when the engine is warm or carries out "Closed loop" control, the ECM provides an optimum performance by catalytic converter and controls the air/fuel mixture in order to obtain theoretical air/fuel mixture ratio.

IGNITION TIMING CONTROL
The ignition power transistor is built in ECM and located in the ignition primary circuit which turns ON/OFF to control the basically remained current to the ignition coil.

It controls the ignition timing in order to provide the optimum ignition timing with respect to the engine operating conditions. The ignition timing is determined by the ECM with engine speed, intake air volume, engine coolant temperature and atmosphere pressure.

OTHER CONTROL FUNCTIONS
1. Fuel pump control: Turns the fuel pump relay ON so that current is supplied to the fuel pump while the engine is cranking.
2. A/C Compressor Clutch Relay Control: Turns the compressor clutch when A/C is turned ON/OFF.
3. Fan relay control: The rates of radiator fan and condenser fan are controlled in response to engine coolant temperature and vehicle speed.
4. Exhaust emission purge control