Quote from: hawkeye93 on July 12, 2017, 10:00:13 AM
Quote from: TopherSho on July 12, 2017, 09:23:02 AM
hmm that confused me. In my old logs my STFT and LTFT are .97 + 1 for 1.97 then. hmmm seems like you guys are more interested in the diff of the two values.
so the formula would be :
LTFT :=(reading-1.0)
plus +
STFT :=(reading-1.0)
------------------
basic result
No, don't add them. LTFT is a long term average of your fuel trim, whereas STFT is a more instantaneous value. Sort of like instant fuel economy vs. average fuel economy.
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It's the way the data is being presented... you do add up the fuel trims for LTFT and STFT to identify the total fueling picture....
As your LTFT even out your STFT will move closer to 1.00....
Example: lean condition is triggered when the ECU sees a total of 25% added fuel to maintain AFR....
So if your LTFT is 1.10 (or +10%) and you have a spike on your STFT of 1.15(or +15%) the ECU will read that as +25% fuel added which is the maximum it can add... then close the throttle to keep from going even leaner on the AFRs.
If your LTFT is 1.00 and your STFT spikes to 1.25 the ECU sees it the same way... +25% and closes the throttle for the same reason as above...
I have logs showing this... the point is, you need to account for LTFT and STFT to understand how the system is running... it's not one or the other...
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