OMEM710 Hardware Manual 2v11
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The fuel map contains the fuel for steady state running. Rapid throttle movements require extra
fuelling.
12.1 Acceleration Fuel
Basic
Accel fuel starts from the parameter +dThottle. This parameter shows you the rate of change of
throttle position. +dThrottle can be modified by TPS Filter. This option allows you to filter out noise
and small throttle movements that should not trigger accel fuel. The lower the value, the greater the
filtering effect. So for any physical rate of change of throttle position, a lower TPS Filter will give a
lower +dThrottle. Typically a value in the region of 50-25 will give sufficient filtering effect yet still
give large enough +dThrottle values to calculate the accel fuel from.
Once you have a +dThrottle from a throttle movement, the next important option is dThrottle
Trigger. This sets the minimum +dThrottle that triggers accel fuel calculations. Typically 3-5. As
soon as accel fuel is triggered the option Accel C gives a set amount of accel fuel. Every amount
above the trigger point also gives Accel M. For example;
dThrottle Trigger = 3
Accel C = 10
Accel M = 3
+dThrottle of 3 would give accel fuel of 10 (Accel C)
+dThrottle of 4 would give accel fuel of 13 (Accel C + Accel M)
+dThrottle of 5 would give accel fuel of 16 (Accel C + 2xAccel M)
Regardless of the amount of accel fuel calculated by this, it is limited to a maximum extra
percentage of the current fuelling by option Accel Limit.
The acceleration fuel is decayed over a number of engine revolutions set by the option Accel
Decay. Low values decay the accel fuel very quickly, high values decay very slowly. It is the
percentage of the accel fuel remaining after each engine revolution. So 0 will give the accel fuel on
one revolution then nothing on the next, 100 will never allow the accel fuel to decay. To find the
required value, have the engine loaded on the dyno and repeatedly trigger accel fuel. If the engine
slowly goes rich then you need to decay the fuel faster.
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