Fuel Injection

Fuel Injection System Schematic:

The Electronic Control Unit (ECU), located in passenger side kick panel, has a microprocessor that receives signals from various input devices regarding engine operating conditions. This information will be evaluated in relation to pre-programmed values and it calculates the optimal injector frequency (opening duration) to provide optimal air/fuel mixture, performance, driveability and emissions output.

Input devices (the ECU receives):

^ Ignition switch signal.
^ Oxygen sensor (lambda sond) signal.
^ Engine speed (RPM) signal from the ignition control unit
^ Knock signal from the ignition control unit
^ Coolant temperature signal.
^ Air mass meter signal.
^ Throttle position signal.
^ A/C control signal from climate control ECU.
^ Turbo over-boost pressure signal.

Output devices (The ECU controls):

^ [1][2]System relay ground.
^ Suppressor relay via the [1][2]system relay.
^ Ballast resistor
^ Fuel injector ground.
^ Idle air valve.
^ Air mass meter signal to the ignition system control unit (ignition ECU input device).
^ Shift indicator light.


START-UP PROGRAM:
The cold engine start-up program provides for two injection periods per revolution. When the engine reaches operating temperature, the ECU provides only one injection period per revolution.

WARM-UP PROGRAM:
This program provides a richer air/fuel mixture until the engine coolant has reached a moderate temperature.

NORMAL DRIVING PROGRAM:
During normal driving, the ECU uses various input devices (mostly the air mass meter signal) to regulate injection frequency.

FULL LOAD AND ACCELERATION PROGRAM:
During full load or acceleration, a richer air/fuel mixture is provided to achieve maximum engine power. This will also keep combustion heat and catalytic converter temperature at an acceptable level.

ANTI-KNOCK PROGRAM:
Knock causes high and dangerous combustion temperatures. Therefore the fuel injection system provides a richer air/fuel mixture to counteract temperature and knock if the ignition and turbo boost systems "anti-knock program" have been unsuccessful at reducing the knock. The ignition system will retard the timing by several degrees and the turbo boost system will disengage to reduce the boost pressure in the intake manifold therefore reducing knock. If knock persists, the fuel injection system will provide a richer air/fuel mixture to eliminate the knocking problem.

SELF ADJUSTING IDLE SPEED FUNCTION:
In time, normal use, wear and coatings will affect the operation of the throttle valve causing less air to enter the intake system. The ECU will adjust the idle speed to these conditions as well as the current engine load (AC operation, headlights....).

SELF ADJUSTING LAMBDA SOND FUNCTION:
The lambda sond (oxygen sensor) operates in a similar fashion. It senses if the air/fuel mixture is rich or lean and the ECU adjusts the fuel injector duration accordingly.
This self-regulating function keeps the air/fuel mixture at a constant midpoint.

EMERGENCY FUNCTION:
There is a "limp home" mode provided when the signal from the air mass meter ceases for some reason (hot wire defect, wiring....). This pre-programmed mode will set the fuel injection frequency (opening duration) so the vehicle can be slowly driven to the repair shop.