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AJ-V8/5HP24
59
Engine Management
Starting
The fueling start strategy operates independent
of accelerator pedal position or movement, with
the exception of a wide open throttle. The ECM
produces steady state running at the target idle
speed within 2 seconds of firing, after an
overshoot of 200 to 300 RPM maximum.
If the accelerator pedal demands a wide open
throttle during cranking, the ECM disables fuel
injection (and signals the throttle valve to the fully
open position) to clear the fuel vapor from a
"flooded" engine.
Warm-up Enrichment
During engine warm-up, the ECM determines the
fuel required from maps which modify an
enrichment factor for coolant temperature,
engine speed and load.
Transient Fueling
During acceleration and deceleration, the ECM
adjusts fueling to optimise the air:fuel ratio for
exhaust emission, response and economy. This
function operates over the full temperature range
for all acceleration and deceleration rates.
Full Load Enrichment
At full load, the ECM inhibits closed loop fueling
and increases the fuel supply to enrich the air:fuel
ratio. Full load is derived from throttle valve
position and engine speed. The degree of
enrichment is dependent on engine speed.
Engine Overspeed Protection
The ECM disables fuel injection if engine speed
reaches 7100 RPM. Fuel injection is re-instated
when RPM falls to 7050.
Stability/Traction Control
If the CAN-FAST TORQUE REDUCTION
CYLINDER message from the BCM requests fuel
intervention, the ECM reduces engine torque by
disabling fuel injection until the throttle valve
reaches its required torque reduction position. It
also changes the CAN-TRACTION
ACKNOWLEDGE message to confirm that torque
reduction is in progress.
Ignition
The ECM supplies two ignition amplifier
modules, which each supply four spark plug
mounted ignition coils. The ECM varies the
ignition timing to optimise power, emissions and
driveability at all operating conditions.
A diagnostic signal from each amplifier module
enables the ECM to monitor the supply to each
ignition coil. If the ECM detects a failure it
disables fuel injection to the affected cylinder.
IGNITION AMPLIFIER MODULES
303-091
Over-run Fuel Cut-off
When the throttle is closed at high engine
speeds, the ECM disables fuel injection until the
engine is at a lower speed. The speeds at which
fuel injection is disabled and re-instated are
mapped against coolant temperature.
On re-instatement the ECM uses a lean air:fuel
ratio, to provide a smooth transition between the
two states, which it then progressively returns to
the nominal. The initial injector pulses are given a
correction value to compensate for cylinder wall
wetting. The ECM derives the air:fuel ratio for re-
instatement from throttle valve position and
engine speed.
During over-run fuel cut-off, operation of the
EVAP valve, EGR valve (where fitted) and closed
loop fueling are inhibited.
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