correct air/fuel ratio by controling injected fuel quantity.
Fuel is directly sprayed into intake manifold beside the intake valve under pressure of
3.5bar. The fuel injector of each cylinder takes correspondingly phase control upon
sequence of air intake and open time of intake valve. Injection terminal is stored in ECU
MAP Diagram and will change with engine speed and intake manifold pressure. ECU can
correct all basic control strategy of engine under all operation condition upon signals from
various sensors in the system.
Idle speed is kept steady by step motor controlling by-pass valve opening and changing
ignition advance angle. Idle speed cannot be regulated manually.
The system utilize inductive discharge ignition, and control time is managed by power
supply module in ECU. Advance angle of ignition is calculated upon engine compression
pressure ratio and air intaked.
3. Fuel Injection System Control Strategy
3.1 Start-up
During the start-up of engine, ECU injects fuel to all cylinders simultaneously to
reduce start-up time, and then injects in phase sequence.
3.2 Idle speed
After start-up, engine needs idling for several minutes to warming up. The normal idle
speed is 880±50rpm(coolant temperature≥85℃). When engine is cold, engine runs at a
high idle speed warming up under the ECU control. With rising of coolant temperature, idle
speed decrease to normal speed gradually. When engine idles, if A/C is turned on, ECU will
increase idle speed by 100rpm.
3.Accelarating
During accelerating, ECU adds fuel injection upon engine load increasing and handles
signals from throttle position sensor, intake manifold absolute pressure sensor and Top Dead
Center/speed sensor. “ Basic Injection Time” multiplies a correction coefficient calculated
upon engine coolant temperature, throttle opening rate and intake manifold pressure
increment. When the injector is closed, if fuel injection time is calculated to have an abrupt
change, ECU will add fuel injection time according to above-mentioned factor, namely
reopen injector and compensate fuel injection as much as possible.
4. Decelerating
During decelerating, engine should reduce fuel injection to decrease exhaust pollution.
ECU identify this stage by high level to low level throttle potentiometer signal but not to
idle speed, and using buffer strategy to reduce torque output. When throttle potentiometer
signal shows throttle is closed and engine maximum limit speed reaches, ECU will regard
the condition is met and reduces by-pass air charge by step motor.
5. fuel cuttingoff
ECU will carry out fuel cutting-off stragety when warm engine speed is over 150rpm
and an idle speed position throttle (throttle potentiometer signal) is identified. During engine
warming up, ECU takes an engine speed of which engine water temperature increasing
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