Inconsistent AFR?

Inconsistent AFR?

Postby Bigfieroman » Wed Sep 02, 2020 10:14 pm

I have been trying to finalize the tune on my supercharged 2007 S2000, but AFR seems to be changing without any changes to the tune. I went out and did 5 back-to-back 3rd gear WOT pulls on the same stretch of road without so much as turning off the engine, let alone changing the tune. Here is a comparison of run 1 and 5:

https://drive.google.com/file/d/1ehryCi ... sp=sharing

Run 5 was a full point richer and was measurably slower, a lot of it was rich beyond the sensor range. MAT and ECT were both ~8 degrees warmer by the 5th run, and based on the compensation tables, the only effect should have been a slight leaning out on the last run due to the MAT High-load comp table (both runs were above the range of the ECT compensation table).

Am I missing something? What else could be affecting fueling if not the MAT and ECT compensation tables?

Things I have already tried:
Injectors professionally cleaned and tested Sat
Replaced MAP sensor
Replaced Fuel Pressure Regulator
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Re: Inconsistent AFR?

Postby KTuner » Thu Sep 03, 2020 11:53 am

Compare fuel pulse to see if that's changing or it's related to the O2 sensor.

Long term fuel trim can alter overall fueling as well.
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Re: Inconsistent AFR?

Postby Bigfieroman » Thu Sep 03, 2020 12:41 pm

I was under the impression that WOT fueling was open loop and not affected by LTFT. Am I mistaken?
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Re: Inconsistent AFR?

Postby KTuner » Thu Sep 03, 2020 1:26 pm

Long term is always applied. Short term, you'll notice, switches to 0 when out of closed loop.
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