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Maf Rescale issues in HP Tuners

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I seem to be having an issue getting my Maf dialed in as accurately as I'd like. After making a maf error histogram in hp scanner and then copy and pasting it into the editor, it seems like the new tune always goes way too far one way or the other and I'm constantly fighting this battle of over correction. I'm using paste special multiply by percent-half when I do this.

For some context I have all the fuel trims disabled and my EQ targets set to 1.00 lambda across the board to assure that's what's always being commanded. I'm following a pretty straight forward process however for example if during one run I have several cells that are up to 4% lean, after doing the multiply by percent half method the next run will end up with those same cells up to 4% rich sometimes with seemingly no rhyme or reason. It makes getting my fuel trims even close to 2-3% a nightmare.

Has anybody else out there ever experienced anything like this using HP Tuners? I had similar headaches tuning the VVE table. If anybody knows what causes this or how to fix it I would appreciate it so so much. This back and fourth game is driving me crazy lol

Attached Files


I applaud your efforts at high precision.

Are you filtering the data for transients?

Are you disabling dynamic airflow to tune MAF by itself when you observe this?

How repeatable is your data if you make no changes?

Are you accounting for commanded EQ ratio changes? You mentioned target is 1.0, but the log shows it does vary at times. In those areas error could appear 4% when it's really only 2% if the target change isn't accounted for in your method. Are you doing monitored lambda * commanded EQ ratio to get a correction multiplier, then halving it?

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