LT headers, rich mixture - chnage commanded AFR?
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From: Sleepy Hollow, NY
LT headers, rich mixture - chnage commanded AFR? I am wondering if anubody has tried to overcome an actual rich condition
after LT installs + cam to change commanded AFR to leaner than 14.63:1.
It seems that with unburned O2 in the exhaust the cars run richer alhtough
the clode loop thinks it is okay. SO if one changed the commanded control point in lcosed loop, AFR to say 15.0:1 that might help to get inot the correct
range? What is wrong with that approach?
Thanks,
Gert
after LT installs + cam to change commanded AFR to leaner than 14.63:1.
It seems that with unburned O2 in the exhaust the cars run richer alhtough
the clode loop thinks it is okay. SO if one changed the commanded control point in lcosed loop, AFR to say 15.0:1 that might help to get inot the correct
range? What is wrong with that approach?
Thanks,
Gert
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Joined: Jun 2004
Posts: 576
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From: Fredericksburg, VA
I think that the problem there lies in the fact that the O2's are only accurate at about 14.7:1 AFR. Sure, you could change the stoichiometric AFR in the PCM to something different, but the O2's wouldn't be able to accurately maintain that AFR.
Question is, are you getting the commanded AFR or are
you getting something else?
And, is the commanded AFR the AFR you tuned in, or is
it being modified by fuel trims that are whacked by the
headers / cam / O2s?
You could tune for open loop and eliminate mistrimming,
or you could play with the airflow mode and proportional
fuel stuff trying to get better results given the O2s'
soggy response in headers cars. Whether the problem
is the cam or the coldness, you'd have to decide by
observing the O2 waveforms.
I think open loop is probably the easiest.
you getting something else?
And, is the commanded AFR the AFR you tuned in, or is
it being modified by fuel trims that are whacked by the
headers / cam / O2s?
You could tune for open loop and eliminate mistrimming,
or you could play with the airflow mode and proportional
fuel stuff trying to get better results given the O2s'
soggy response in headers cars. Whether the problem
is the cam or the coldness, you'd have to decide by
observing the O2 waveforms.
I think open loop is probably the easiest.
