MAF tuning and AFR correction
Thread Starter
Teching In
Joined: Jun 2008
Posts: 26
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From: Alvarado, TX
MAF tuning and AFR correction The long version.
Short version, tuning MAF table using HP Tuners and WB. The usual stuff is turned off/disabled as required.
Question 1: When tuning MAF do you filter out deceleration data?
Problem 1: When decelerating, part throttle or closed throttle it does not matter, AFR goes rich. This data lowers the MAF table causing it to read lower than stock in the < 6k Hz range. Above 6k it is up to 14% higher than stock. Fuel trims are reading up to 9.8 in CL.
Question 2: In CL actual AFR never equals commanded AFR, always rich, why?
Problem 2: Probably unrelated, when going back into CL AFR is adjusted to ~14.3 instead of the commanded 14.63. New O2s changed nothing, adjusting switch points changed nothing.
For now I just added 10% to the MAF table under 6k and my LTFTs are between 0.8 and -2 but I would really like to know what I am doing wrong on the MAF tuning to cause it to be so far off. And the AFR still corrected back to ~14.3 after the trims learned.
Short version, tuning MAF table using HP Tuners and WB. The usual stuff is turned off/disabled as required.
Question 1: When tuning MAF do you filter out deceleration data?
Problem 1: When decelerating, part throttle or closed throttle it does not matter, AFR goes rich. This data lowers the MAF table causing it to read lower than stock in the < 6k Hz range. Above 6k it is up to 14% higher than stock. Fuel trims are reading up to 9.8 in CL.
Question 2: In CL actual AFR never equals commanded AFR, always rich, why?
Problem 2: Probably unrelated, when going back into CL AFR is adjusted to ~14.3 instead of the commanded 14.63. New O2s changed nothing, adjusting switch points changed nothing.
For now I just added 10% to the MAF table under 6k and my LTFTs are between 0.8 and -2 but I would really like to know what I am doing wrong on the MAF tuning to cause it to be so far off. And the AFR still corrected back to ~14.3 after the trims learned.
The difference between your commanded A/F and your W/B readings is probably nothing more than the accuracy of the W/B. Don't over complicate it. I could care less what the difference is, I care more what the FT % is.
As for the enrichment on decel, personally, I tune MAFs on a dyno, and use a very slow gradual increase in throttle position, taking care to let the engine stabilize in each MAF cell. I've found that this yields the most accurate results. If you're doing it on the street, gradually speed up, very slowly, and highlight and copy the table before you decelerate. You'll never get it perfect. You're only trying to get it to a reasonable limit of correction.
As for the enrichment on decel, personally, I tune MAFs on a dyno, and use a very slow gradual increase in throttle position, taking care to let the engine stabilize in each MAF cell. I've found that this yields the most accurate results. If you're doing it on the street, gradually speed up, very slowly, and highlight and copy the table before you decelerate. You'll never get it perfect. You're only trying to get it to a reasonable limit of correction.
Thread Starter
Teching In
Joined: Jun 2008
Posts: 26
Likes: 0
From: Alvarado, TX
As for the enrichment on decel, personally, I tune MAFs on a dyno, and use a very slow gradual increase in throttle position, taking care to let the engine stabilize in each MAF cell. I've found that this yields the most accurate results. If you're doing it on the street, gradually speed up, very slowly, and highlight and copy the table before you decelerate. You'll never get it perfect. You're only trying to get it to a reasonable limit of correction.
