Why I THINK a tune isn't necessary 321WHP

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To add to the above, one of the things I gathered from UpRev's detailed docs that definitely could be worth fine-tuning regardless is the MAF table. Basically, the stock MAF table is a rough approximation, and there are manufacturing variances in the MAF voltage readings as they compare to reality. On the dyno you can adjust those tables to get your MAF tables correct for the exact sensor variations in your own car (not to mention intake diameter changes).

With MAFs being accurate (and with stock intake pipe size, they probably aren't hugely far off), I think it's true that the O2 feedback + MAF is good enough regardless of exhaust setup, and it definitely does learn long-term trims. But yes, every ECU reset it'll have to re-learn, and so that goes faster and smoother if the baseline is closer and less adjustment is needed.

Re: AFR targets, that's not really about compensating for inaccuracy, that's just about deciding what AFR you want to run (safety margin, temps, etc... I even found that bumping my AFR a little richer in the upper left of the table (low RPMs, low throttle) helped a bit with tip-in fueling coming out of the bottom there, at the expense of wasting a little fuel.

The open-loop thing, yeah, not sure how well the car adapts there. Surely the long-term trims learned during closed-loop would apply to the calculations done from the MAF data? Honestly I don't know.

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