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Fuel trim variations based on variables (load, RPM, etc.)

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Hi all,

I have not been able to figure out if this is a normal phenomenon or if there is something else at play here.

Have a look at the image:

- These are 2 separate logs recorded minutes apart. 6th gear (left) and 2nd gear (Right)

- The MAF Voltage and MAF flow rate is virtually the same value

- RPM, load and ignition advance are different between the logs

STFT is showing a significant difference between the logs, why? Which one do I trust?

Based on the AFR that needs to be compensated (14.55->14.7), I am going to trust the lower STFT, but I wanted to understand why this may happen.

Thanks in advance!

Phil.

Attached Files

What is the throttle position (not pedal position) and coolant temp? Any chance that some other compensation (like WOT enrichment, or coolant temp) is is different between the two operating conditions?

Since neither of those cases are steady state (the Engine RPM is increasing) - I wouldn't trust either of the fuel trims. Try testing with the RPM not changing for about 1-2 seconds -- then see that the trims are -- give it time to adjust.