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Ideal AFR's while shifting

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I am looking to better tune my Accel Enrichment. What would be your suggested AFR target while shifting between gears (street car) at light to medium throttle?



What do you mean? The accelerator pushing after a gear change? AFR should match your Target AFR without lean or rich spots

Thank you for the reply.

I see the question needs further clarification - starting at idle 1st gear, push acc. pedal to TP 10%, release acc. pedal, shift to 2nd, push acc. pedal to TP 10%, repeat for 3rd and 4th. Then apply the same process to TP 20%. Note that at no time is the engine under boost. Are you saying that the goal should minimal or no fluctuation from the target AFR at any point in the shift process?

With this there is a second question. While at cruise, 2000 rpm and TP 15%, tap the acc. pedal to approximately 25%, should there be a swing in AFR (target set at 14.7) and if so how much? Example - tap throttle, richens mixture to 12.5 AFR then the ECU quickly corrects to target 14.7.



Now we are talking only about transistent acceleration events. During deceleration generally you don't need fuel at all on a street car and you could enable decel cut feature in the ecu.

The main reason that you should add fuel during acceleration event is that when you rapidly change the air pressure near injector nozzle, the injected fuel tend to

condense on the runner wall, making evaporation worse. So you should add some more fuel in order to provide enough mass, needed for the engine right now. But anyway it's extra fuel and that mass that was condensed on the runner wall will evaporate on next cycles and enter the cylinder later, making the AFR sightly rich, how much - depends on the engine design. Also when load rapidly changes there is a delay between air pressure change and ecu approaching correct signal from map (for example long or thin vacuum hose to map sensor increasing that delay). Combination that 2 factors gets the answer how much you should add. If you have 12.5 rich spot, you could decrease enrichment and see how it works and keep going until you see the performance degradation or until AFR timing curve become flat with no fluctuactions. In first case make a step backward in second case just stop.

Also look at the ecu functionality, some old ecu's have very primitive tactics of controling transistent throttle events and you would't be able to make it perfect.

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