adjusting ltrims with LS1 edit ?
02-25-2002, 07:40 AM
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Staging Lane
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adjusting ltrims with LS1 edit ? My ltrims are running in the 22-25 range and the car is dog rich @ wot. I can get the 02`s correct @ wot, but I need to get the ltrims stable before worrying with that. My question is how do I adjust the ltrims? I assume its the MAF but I havent a clue as to the direction to go? Any help would be great!!
02-25-2002, 07:25 PM
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Re: adjusting ltrims with LS1 edit ? I was running between 15% to 20% for the Ltrim fuel on my '99 SS.
I'm assuming that you have LS1_Edit.
With LS1_Edit, I would do the following changes to the MAF table:
1500Hz to 6000Hz: multiply by 120%
6125Hz: multiply by 119%
6250Hz: multiply by 118%
6375Hz: multiply by 117%
and so forth until you multiply by 101%, then stop
Flash this new program back onto your PCM.
This technique reduced my Ltrims down to a range from -5% to 0%.
Do a PCM reset and go out and drive the car around for about 15 minutes then do some ATAPing.
It worked for me.
If you have a MAFT, then set the base switch to 20% rich, and do a PCM reset, drive the car for 15 minutes and again ATAP the car.
I hope this helps.
See what is happening is that the PCM reads a flow value out of the MAF table and computes a pulse width. The MAF value is too low for what is actually flowing into the engine. So the PW is too short to begin with and the PCM learns that there is a lean condition and then bumps up the Ltrim fuel values. By increasing the values in the MAF table, the PCM will calculate a longer PW and you will end up running closer to 14.73 AFR.
Accordingly, the Ltrim fuel will be reduced.
I'm assuming that you have LS1_Edit.
With LS1_Edit, I would do the following changes to the MAF table:
1500Hz to 6000Hz: multiply by 120%
6125Hz: multiply by 119%
6250Hz: multiply by 118%
6375Hz: multiply by 117%
and so forth until you multiply by 101%, then stop
Flash this new program back onto your PCM.
This technique reduced my Ltrims down to a range from -5% to 0%.
Do a PCM reset and go out and drive the car around for about 15 minutes then do some ATAPing.
It worked for me.
If you have a MAFT, then set the base switch to 20% rich, and do a PCM reset, drive the car for 15 minutes and again ATAP the car.
I hope this helps.
See what is happening is that the PCM reads a flow value out of the MAF table and computes a pulse width. The MAF value is too low for what is actually flowing into the engine. So the PW is too short to begin with and the PCM learns that there is a lean condition and then bumps up the Ltrim fuel values. By increasing the values in the MAF table, the PCM will calculate a longer PW and you will end up running closer to 14.73 AFR.
Accordingly, the Ltrim fuel will be reduced.
