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ECM fuel map question (guru needed)

M

maybe2fast

NAXJA Forum User
Location
COMMERCE, MI
first please familiarize yourself with this thread
http://www.naxja.org/forum/showthread.php?t=979735

I am curious about the computers fuel map. I am running in the -10% to -15% long term fuel trim of the ECM map. I am wondering if running in this map is causing poor mpgs

I have LT1 injectors and the ECM adjusted fine, the short term is right around 0% and the long stays in the negative range.

Is this map that the ECM is in less "advanced"?

I mean is it a "slow" or default like map?

O2 switches great, no cracked manifold and truck runs well.
 
The reason that your stft is 0 is because the pcm already logged enough stft to determine that the ltft needs to be -10-15% to make the lt1s spray the right amount of gas to make the 14.7 afr in closed loop. I forget the min/max %, but I think it is +/- 30-39%; the pcm can handle the lt1s just fine. Get yourself a wideband o2 and see what afrs you get in open loop(>70% throttle and/or right around 3Krpm) to see if you are running extra rich(12.5-12.8afr is what you want, any lower and you're wasting gas). If you are lower, you might want to build/buy an adjustable map to dial back the wot/open loop afrs.
 
gradon said:
The reason that your stft is 0 is because the pcm already logged enough stft to determine that the ltft needs to be -10-15% to make the lt1s spray the right amount of gas to make the 14.7 afr in closed loop. I forget the min/max %, but I think it is +/- 30-39%; the pcm can handle the lt1s just fine. Get yourself a wideband o2 and see what afrs you get in open loop(>70% throttle and/or right around 3Krpm) to see if you are running extra rich(12.5-12.8afr is what you want, any lower and you're wasting gas). If you are lower, you might want to build/buy an adjustable map to dial back the wot/open loop afrs.
Click to expand...

I couldn't have put it better myself.
 
I was just wondering if being in the -10 to -15 table, is a slow responding table? Like is the ECM checking things slower or adjusting things slower?
 
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