Timing/Fuel Targets at Idle

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imstimpy
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Timing/Fuel Targets at Idle

Post by imstimpy » Tue Jul 11, 2017 11:40 am

I'm looking to understand (and alter) timing and fuel under idle conditions. I have a modified manifold and throttle so the airflow characteristics do not match OEM. As a result, timing is floored at -1/0/1, AFR is relatively stable at 14.7-15.0, and an occasional stumble/misfire can be felt alongside a slightly rough idle.

* What conditions or triggers does the ECU use to switch into an idle state?
* What dictates the timing values at idle?
* What dictates the fuel pulse at idle?
* What is the suggested strategy or table alterations to achieve a proper idle?

Per my research, all I can find is this thread discussing the Throttle flow vs opening table. In the thread, Hondata alludes to some derived ignition strategy controlled by the assumed airflow.

Thank you!

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Hondata
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Re: Timing/Fuel Targets at Idle

Post by Hondata » Tue Jul 11, 2017 1:11 pm

* What conditions or triggers does the ECU use to switch into an idle state?
Throttle is closed and the rpm is less than ~ 1800 rpm.

* What dictates the timing values at idle?
The ECU controls the idle speed using ignition, so it is an internal calculation. ie not the ignition tables.

* What dictates the fuel pulse at idle?
The fuel tables.

* What is the suggested strategy or table alterations to achieve a proper idle?
I suspect the problem is that your throttle flows too much air when closed. The ECU is then reducing the ignition timing to keep the idle speed down, and you're getting misfires from too little timing.
Hondata

imstimpy
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Re: Timing/Fuel Targets at Idle

Post by imstimpy » Tue Jul 11, 2017 3:04 pm

Thank you for the timely response.

So the timing tables are not active at idle because it is an idle-control strategy but the fuel tables are active? I'll modify the airflow table to see if timing comes and I'll also look further into fuel adjustments. The fuel adjustments didn't appear to affect the STFT via Live Tuning as I would have expected but I didn't explore too far.

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Re: Timing/Fuel Targets at Idle

Post by Hondata » Wed Jul 12, 2017 9:09 am

Be aware that it probably is the throttle flowing too much air when closed, and that adjusting tables will not fix the problem.
Hondata

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