Quote:
Originally Posted by ShadowReaper
The only thread I found useful to help me understand Fuel Trims, the OP had 100 Octane.
I moved from Florida where they have 93 Octane, to Colorado where 91 is the highest. I'm JDL Turbo'd tuned. To make this clear, I have NOT been getting insane Fuel Trim reads like (-28 or +30). However, the trims seem to love being in the Negatives. It does not look normal to me.
Keep in mind that I noticed this issue couple days after I got a revision from my tuner (due to the move) I went for a test drive to see what my Fuel Trims looked like.
On Idle
ST: Lowest: -4.7 Highest: 0.8
LT: Lowest: -4.7 Highest: -1.6
On normal driving:
ST: Lowest: -11.7 Highest: 2.3
LT: Lowest: -3.6 Highest: 0.8
Again my point is that I am heavily on the negative side. I was on 91 octane for around a week before the revision and I didn't see readings like this, this is why I don't think it was just the switch to 91 form 93.
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That's pretty good by my account. I think the temperature correction factors are a bit off on the OEM tune for some reason, so my winter ltfts are negative and summer is positive. I don't think anyone actually messes with temp correction. Colorado is likely a bit colder and dryer than Florida being my point.
Stft will vary quite a bit. Every squirt of gas is a bit different so it takes into account very short term (like 2-4 revolutions) trends and adapts immediately. I don't think twice about anything less than +-15 on these.
Ltft stores longer term trends based on stft. I'm usually ok with +-5 on these. Some people are more picky. Your ltft looks like it might decrease to about -5 or -6 all things being equal, based on your stft range.
Don't worry about idle and low rpms unless they get real bad(10+%).
I'd wait for temperatures to get into the 60 or 70s then see how it looks. If they get below -10, then you should start looking for a solution IMO.