Limit fuel trims to 2%?

[dbb2797]

If I wanted to limit fuel trims to 2% where would I make that change to limit? Would it be max learn limit or integral gain? I'm looking to keep fuel trims to a well defined range so as to prevent large fueling adjustments at WOT.

[Jn2]

If you want to prevent fueling adjustments you need to dial in the MAF curve, once dialed in your fuel trims should be +/-3% with out you needing to adjust anything. If you are seeing fuel trims that are way off that is because your tune needs more work, not bc you need to limit how much they can adjust.

[dbb2797]

If you want to prevent fueling adjustments you need to dial in the MAF curve, once dialed in your fuel trims should be +/-3% with out you needing to adjust anything. If you are seeing fuel trims that are way off that is because your tune needs more work, not bc you need to limit how much they can adjust.

I understand what you are saying, and it most cases your point is true. But if I understand MAF adaption correctly, the ECU will be normalizing the MAF all the time. And if you drive your car all the time, you won't see as big of fuel adjustments after you've dialed it in.

I on the other hand only race my car. So I may only drive it once a week. I dialed in the MAF on the road. Took it to the track and everything was great within 2-3% adjustments at WOT. The next week the temperature was 15 degrees higher and my first pass the car was making 7% adjustments. So it appears that large fluctuations in temperature can cause large corrections even after you've dialed it in. Unless you are always driving the car and the ECU can make incremental adjustments on a day to day basis.

Dialed in or not. I need to make 100% sure the ECU doesn't make drastic fuel adjustments at WOT.

[06300CSRT8]

Ok but you do realize those adjustments make your stoich be where you're asking it to be, so in the instance where it was adding 7% last time, your car would have been lean as hell if you had limited your fuel learning. Not really sure what you're trying to accomplish, what vehicle is this for? Newer fords don't "average" your cruising trims and then add the average to your WOT fueling, it's in closed loop the entire time and adjusting on the fly based on real readings the entire time.

[dbb2797]

Ok but you do realize those adjustments make your stoich be where you're asking it to be, so in the instance where it was adding 7% last time, your car would have been lean as hell if you had limited your fuel learning. Not really sure what you're trying to accomplish, what vehicle is this for? Newer fords don't "average" your cruising trims and then add the average to your WOT fueling, it's in closed loop the entire time and adjusting on the fly based on real readings the entire time.

Sorry I should have mentioned that it's for a coyote engine (2011 mustang). The adaption I was referring to is "maf adaptation" which the copperhead has enabled by default. Also, this is strictly for a racing application. I use a 2-step and while on the 2-step I am in open loop. When I come out of open loop the fueling is going to show abnormally lean and is immediately going to start adding fuel when it shouldn't be. This is compounded when there are large temperature differentials between racing days. I'm confident of my MAF curve being dialed in. But my datalogging shows that no matter how dialed in my MAF is, it will always take up to about 5500 RPM's before the fuel readings start to show accurate readings when coming off a 2-step. Instead of shutting off fuel trims completely, I want to limit the fueling adjustments=. I need the fueling to be consistent.

[murfie]

Are you looking at your actual lambda? I'm sure its pretty consistent. short term fuel trims make sure of it in closed loop and adaption does in closed loop. You can disable cylair anticipation.
The MAF sensor works by a heated wire, It keeps a wire at a temperature like 200* its pretty accurate at measuring airflow regardless of temperature. If you look at the MAF tempature compensation table its 1-2% with the exception of rare high or low tempatures and even then its most at very low air flow.

There absolutely no good reason to limit short term fuel trims or commanded lambda, unless you want your fueling to be inconsistent. If you don't want it to learn and apply in cases like coming out of 2 step, disable the LTFTs and cylair adaption.

IF you really want to, You could lower the proportional values in the closed loop PI. Its a direct modification to the error calculated from the O2's.
Integral will just "smooth" the applied correction making it react slower.

[dbb2797]

Are you looking at your actual lambda? I'm sure its pretty consistent. short term fuel trims make sure of it in closed loop and adaption does in closed loop. You can disable cylair anticipation.
The MAF sensor works by a heated wire, It keeps a wire at a temperature like 200* its pretty accurate at measuring airflow regardless of temperature. If you look at the MAF tempature compensation table its 1-2% with the exception of rare high or low tempatures and even then its most at very low air flow.

There absolutely no good reason to limit short term fuel trims or commanded lambda, unless you want your fueling to be inconsistent. If you don't want it to learn and apply in cases like coming out of 2 step, disable the LTFTs and cylair adaption.

IF you really want to, You could lower the proportional values in the closed loop PI. Its a direct modification to the error calculated from the O2's.
Integral will just "smooth" the applied correction making it react slower.

Awesome, thanks Murfie! This is exactly the info I was looking for.

[wbt]

If you want to prevent fueling adjustments you need to dial in the MAF curve, once dialed in your fuel trims should be +/-3% with out you needing to adjust anything. If you are seeing fuel trims that are way off that is because your tune needs more work, not bc you need to limit how much they can adjust.

x2