Geely EC715 2009, Workshop Manual

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2.2.3 System Working Principle
2.2.3.1 System Working Principle
ECM calculates the basic fuel injection duration, Air-Fuel ratio
close to the ideal mixture for the engine, and controls engine
operation based on the engine's intake air quantity and engine
speed signal. For example, in cold start, according to related
signals, ECM increases the fuel injection and controls idle
speed control valve actuator, to achieve a smooth start and
controls the engine idle speed. In addition, ECM also has the
fault self-diagnosis and protection function, when the engine
fails, ECM can automatically diagnose and preserve the DTC
code and, sends a warning through the fault indicator light. The
stored code can appear again in certain trigger conditions.
Once the sensor or actuator fail, ECM automatically start the
backup system, to ensure the safety of the vehicle, maintain
the vehicle driving ability. ECM can also communicate with
scan tool. Scan tool can be used to read the stored DTC code
and scan the current ECM operating system parameters, that
is the data stream. Scan tool can also be used to drive the
control system actuators for test, which provides a great
convenience to diagnostic.
2.2.3.2 Fuel Injection Quantity Adjustment
At Startup, ECM calculates fuel injection time based on the
engine speed, engine coolant temperature signal. After startup,
ECM determines the basic fuel injection quantity based on the
intake manifold absolute pressure sensor. After determining
the basic fuel injection quantity, according to the different
engine operating conditions, ECM adjusts the fuel injection as
following:
– Start Up-Enrich Mixture: Starting condition is when the
engine speed is below the specified value, the ignition
switch is ON. Especially in the low temperature, in order to
improve startup performance, ECM increases fuel injection
time, and enriches the mixture.
– After Start-Enrich Mixture: The engine has just started, in
order to maintain its running stability, ECM increases fuel
injection amount according to the engine coolant
temperature.
–
Warm Up-Enrich Mixture: The engine temperature is low,
gasoline evaporation is poor, ECM provides rich mixture.
ECM increases fuel injection amount according to the
engine coolant temperature.
–
Heavy Load-Enrich Mixture: The engine power output is
maximum, in order to ensure the engine work properly,
ECM increases fuel injection duration according to throttle
position, engine speed, air flow, engine coolant
temperature signal. Increased fuel amount is up to 8%
-30% of normal fuel injection amount.
– Acceleration-Enrich Mixture: When the engine is
accelerating, for it to have dynamic, enrich the mixture.
ECM increase the fuel injection amount according to air
flow, engine speed, vehicle speed, throttle position (change
rate), the engine coolant temperature sensor signal.
– Intake Air Temperature Adjustment: Air density changes as
the temperature changes. In order to maintain a more
accurate Air-Fuel ratio, ECM uses air density at 20°C
(68 ºF) as the standard value. ECM adjusts fuel injection
according to measured intake air temperature signal. At low
temperature, ECM increases fuel injection amount. At high
temperature, ECM decreases fuel injection amount. The
adjustment is up to 10%.
– idle Stability Adjustment: In the engine control system,
when the intake manifold pressure increase, the idle speed
drops. ECM adjusts fuel injection amount according to
throttle position, engine speed, intake manifold absolute
pressure sensor signal.
–
Air-Fuel Ratio Feedback Adjustment: ECM adjusts fuel
injection amount according to oxygen sensor signal. When
engine starts, the mixture will be enriched. With heavy load,
the engine coolant temperature below the set temperature
and fuel supply cut off operating conditions, ECM is in
close-loop control mode.
– Cut Off Fuel Supply: In order to achieve good fuel economy,
lower emissions pollution, when the engine is in forced idle
state, ECM cut off fuel supply temporarily according to
throttle position, engine speed, engine coolant temperature
sensor signal. During emergency deceleration, engine over
speed, vehicle over speed, fuel supply will also be cut off
temporarily.
– Voltage Adjustment: Power supply voltage affects fuel
injection amount. When voltage is low, the actual injection
duration is shorter than normal and the mixture is lean. It
needs to be adjusted. ECM adjusts fuel injection amount
according to high or low voltage. Power supply voltage
signal is from the battery.
Engine Control System JL4G18-D 2-23
EC718/EC718RV EC715/EC715RV 10/2009