OMEX OMEM710 - Tuning Warm-Running Acceleration Fuelling

OMEM710 Hardware Manual 2v11
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Tuning Warm-running Acceleration Fuelling
Your startup calibration will be preset with typical acceleration fuelling values, and if the engine
‘feels’ right then this is in many cases quite acceptable – engines will usually feel right when they
have enough, or too much, acceleration fuelling, and will only feel wrong if there is too little fuel or
far too much. On many engines the following very simple setup will be suitable;
 Get the engine to normal running temperatures
 Set the TPS Accel RPM table and Accel Throttle Trim table to 100% throughout
 Set TPS Filter to 75%
 Accelerating the engine in the most difficult condition, fast throttle movement from idle, adjust
option Accel Limit until the engine accelerates at the maximum rate possible with no stumbles.
 Adjust TPS Filter to the lowest value possible that still gives engine acceleration without
stumbles in all conditions.
For absolutely correct setup, the following procedure should be followed;
 Set the TPS Accel RPM table, Accel Throttle Trim table, and Accel Coolant Trim table all to
100% throughout.
 Disable the acceleration fuelling by setting the dThrottle Trigger value to an unobtainable value
such as 100.
 The condition that requires the most acceleration fuel is getting the engine to come up from idle
so we start there. By viewing the parameter +dThrottle and gently pressing the throttle pedal,
find the value of +dThrottle at which the engine will have a lean ‘stumble’ (this can be
recognised either by a wideband lambda reading, or simply by listening to the engine and
seeing when it stops ‘picking-up’ smoothly). Enter this value into option dThrottle Trigger
(typically this would be 2 or 3).
 With Accel M set to 1, adjust Accel C until the engine will accelerate from idle with no lean
stumble at a throttle movement just fast enough to trigger the acceleration fuel.
 Adjust Accel M until the engine will best accelerate from idle at the fastest rate of throttle
movement that can be achieved.
 Accelerate the engine at the fastest rate of throttle movement possible, starting from the engine
speeds shown in the TPS Accel RPM table. Reduce the values at each engine speed in this
table to give the minimum possible value that still gives maximum engine acceleration or an
acceptable lambda value.
 If using a rolling road, then it is also possible to trim the response based on throttle start position
in the Accel Throttle Trim table as a load can be applied to the engine to allow the throttle to
be held at varying % openings and the table trimmed based on the lambda values recorded.
 Tuning the Accel Decay also requires the use of a rolling road to get it perfect. With the vehicle
being driven with load on it, repeatedly trigger acceleration fuel by pumping the throttle, but with
the engine unable to accelerate too quickly due to the load on it. If the lambda values steadily go
rich, then reduce the Accel Decay value, or if the lambda values steadily go lean, then increase
the Accel Decay value.
Tuning Cold-running Acceleration Fuelling
The cold-running acceleration fuelling must be set whilst setting other cold running tables and
options. Refer to the cold running section of this manual for further advice.
12.2 Deceleration Fuel Cut Off
When this function is active ie above the engine RPM and below the engine load, the injection
pulsewidth is reduced to a minimum. This feature is not normally used on high performance and
race cars as it is simply there to improve fuel economy slightly. To disable this feature set as follows.