OMEM710 Hardware Manual 2v11
37
Set Idle Hi FB Target + to 0 so that the engine always has the same target idle speed.
If there is an adjustable air bleed screw or an adjustable throttle stop, set all warm temperatures
in the Idle Duty Coolant table (typically above 60degrees) to 0, then with the engine warm set
the natural idle to 100 or 200rpm below the target idle speed using the throttle stop or air bleed
screw (note that if you move the throttle stop you must reset TPS min), then increase all hot
temperatures in the Idle Duty Coolant table to a value which allows the engine to idle at the
target idle speed. If there is no mechanical idle adjustment then set all hot temperatures in the
Idle Duty Coolant table to a value which allows the engine to idle at the target idle speed.
Turn the scatter spark control and motor feedback control back on by resetting the Idle on
below RPM option to its previous value. (typically 500rpm above the normal target idle speed).
Blip the throttle and the engine speed should return to the Idle FB Target RPM value.
Follow the Setting Hi Idle instructions below.
During cold running setup of the fuelling, you will also need to adjust the Idle Duty Coolant table at
each temperature to ensure that the feedback controls have to do as little work as possible. As a
start point set all cold temperatures to 10% higher than the warm temperatures. The feedback work
can be seen in parameter Idle Set. If Idle Set is a positive number then increase the current value in
the Idle Duty Coolant table, or if negative, then reduce it.
Setting air bypass idle control on TPS for load engines
On TPS load based engines, the ECU does not measure the extra air flow due to the opening of the
idle motor, so does not compensate with extra fuel in the main fuel map to maintain the target
lambda (air/fuel ratio). An oxygen sensor cannot make adjustments to the fuelling fast enough to
cope with these changes. The Idle Fuel table allows a fuel trim based on idle motor duty to maintain
a constant lambda value. To set this table correctly, the engine must be held at the idle target speed
whilst the engine is put under varying loads to alter the opening of the idle motor. This can be
achieved through the use of a rolling road to apply the load, or simply by holding the brakes of the
vehicle and gently releasing the clutch to load the engine. The table should then be altered to
provide the extra fuel required to maintain a constant lambda value.
1. Get the engine to normal running temperatures
2. Set Idle Hi FB Target + to 0 so that the engine always has the same target idle speed.
3. Set Idle FB+ Max and Idle FB- Max both to 0.
4. Set the whole of the Idle Scatter Spark Table to 0 (noting the values in this table as you will
need to re-enter them later)
5. Set the whole of the Idle Duty Fuel Trim Table to 0.
If there is an adjustable air bleed screw or an adjustable throttle stop;
6. Set all warm temperatures in the Idle Duty Coolant table (typically above 60degrees) to 0, then
with the engine warm set the natural idle to approximately 250rpm below the target idle speed
using the throttle stop or air bleed screw (note that if you move the throttle stop you must reset
TPS min). Ensure that the engine is running at the correct AFR as the wrong AFR will make the
engine run slowly. Change the fuelling in the main Fuel Map as required to maintain the correct
AFR.
7. Set the whole of the Idle Duty Fuel Trim Table to 30%
8. Increase all hot temperature values in the Idle Duty Coolant table to a value which allows the
engine to idle at the target idle speed whilst simultaneously adjusting the fuel map to achieve
the correct AFR at the idle speed.
9. Ensure that the main Fuel Map is calibrated correctly down to stall speeds and at both closed
throttle and the first site above closed throttle. This is best achieved through loading the engine
on the dyno. Typically, as the engine goes towards stall speeds, there is a large increase in
fuelling requirements.
10. In the Idle Duty Coolant Table, set various openings of the idle motor from 0-100%, load the
engine on the dyno to hold (approximately) the target idle speed, then adjust the Idle Duty Fuel
Trim Table to maintain the correct AFR.
11. Return all warm temperature values in the Idle Duty Coolant Table to a value that maintains
the target idle speed.
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