Why negative fuel trims after autoVE

[stigmundfreud]

Cheers Joe, its coming back and that matched what I thought (of course ) about the 1.25 being extra being applied. Of course we have the wideband in now so will log purely on that (gave up on the idea of trimming with the ltft bens and waited). Should be a fun night assuming the replacement LC1 works

[joecar]

Sanity check the LC-1 by checking Lambda it returns while PCM is commanding CL.

[SSpdDmon]

My thoughts on LTFTs from 2 years ago - see post #6.

http://www.ls1tech.com/forums/pcm-di...uel-trims.html

Sounds like the OP has stumbled upon some similar questions. If I ever tune a car again to use the fuel trims, I think I might actually target a +5% across the board...not the -1% to -4% that I remember seeing everywhere I looked back in the day.

[mr.prick]

LTFTs are impacted by the dynamics tables as well.

After installing some new fuel injectors (ASA 38lb) with their "known" offsets,
LTFTs under decel were highly negative.

I reduced the impact & evap factors by X.XX% and got them inline.
This may have been needed because of the extra CI my engine has now.
Otherwise the "known" injector settings may have worked.

High positive & high negative LTFTs can cause severely incorrect fueling.

[Gelf VXR]

I have found that slightly positive trims gave me some knock pretty evenly across the map, I'm at the limit of the knock threshold for g cyl. What this has showm me that the GM Hi octane map is the correct shape for my set up, for the solution I have moved the Hi octane map all one cell to the left. I will add back incremenatally until I see knock in any cells.