spark advance question !! help !!
08-16-2014, 03:59 AM
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spark advance question !! help !! recently i got my lq4/t56 into my mazda and when testing/driving with no hood on the car ran great …. then we put a hood on and i noticed the air intake temp went up to 140 … compared to 70- 80 degrees
now when this happened my spark advance went down to 12 at WOT so i figured easy fix … take the hood back off so i did so and the car is seeing cooler air temps but is still only 12 - 14 at WOT compared to 19-20 which is should be at tried to reset the fuel trims disconnect the battery and still nothing !ALL SENSOR DATA IS NORMAL no knock either so my question is how do i fix this !! my friend told me to zero out my air intake temp table or something like that ?
my car is not unlocked yet it is a factory tune !
motor 07 chevy express lq4
pcm 03 gmc savanna
now when this happened my spark advance went down to 12 at WOT so i figured easy fix … take the hood back off so i did so and the car is seeing cooler air temps but is still only 12 - 14 at WOT compared to 19-20 which is should be at tried to reset the fuel trims disconnect the battery and still nothing !ALL SENSOR DATA IS NORMAL no knock either so my question is how do i fix this !! my friend told me to zero out my air intake temp table or something like that ?
my car is not unlocked yet it is a factory tune !
motor 07 chevy express lq4
pcm 03 gmc savanna
08-16-2014, 11:26 AM
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I think you should not listen to your friend about tuning.
IAT spark retard is there for a reason. That being, hot
air pings worse. Ping enough and the PCM will learn
toward the low octane table, and remember for a while.
You would look at your Knock Learn Factor, if you were
scanning.
Now you have the question of real in-taken air temp
vs sensor air temp, which a cold air setup attempts to
fix the first but may not touch the second, depending.
If removing the hood makes the IAT read cooler but
does not affect the actual air path / temp, you would
run more advance. Maybe in regions where more is not
better. Especially untuned or hack-tuned, unknown
fuel pressure and mysterious exhaust and who knows
what-all. Get into ping, especially in regions of operation
where you spend steady time, and large knock learning
can result pretty quick. Unlearning, that needs time-
not-pinging.
People reduce or eliminate the difference between main
and low-octane timing tables to minimize the effect of
this learning, when things go south. But this is exactly
when you want to have somewhere soft to fall. Before
you go taking last decade's advice about tuning methods,
I suggest you go back to basics, bottom-up, and get a
safe, not necessarily maximum enjoyment, street tune
that just doesn't complain or misbehave or deliver AFR
that disagrees with what you commanded. Then you
have something solid to work from, not a holed piston
waiting for bad weather to happen.
IAT spark retard is there for a reason. That being, hot
air pings worse. Ping enough and the PCM will learn
toward the low octane table, and remember for a while.
You would look at your Knock Learn Factor, if you were
scanning.
Now you have the question of real in-taken air temp
vs sensor air temp, which a cold air setup attempts to
fix the first but may not touch the second, depending.
If removing the hood makes the IAT read cooler but
does not affect the actual air path / temp, you would
run more advance. Maybe in regions where more is not
better. Especially untuned or hack-tuned, unknown
fuel pressure and mysterious exhaust and who knows
what-all. Get into ping, especially in regions of operation
where you spend steady time, and large knock learning
can result pretty quick. Unlearning, that needs time-
not-pinging.
People reduce or eliminate the difference between main
and low-octane timing tables to minimize the effect of
this learning, when things go south. But this is exactly
when you want to have somewhere soft to fall. Before
you go taking last decade's advice about tuning methods,
I suggest you go back to basics, bottom-up, and get a
safe, not necessarily maximum enjoyment, street tune
that just doesn't complain or misbehave or deliver AFR
that disagrees with what you commanded. Then you
have something solid to work from, not a holed piston
waiting for bad weather to happen.