Originally Posted by tunaglove
You are correct, but the STFTs are an instant reaction to the voltages of the O2 sensor feedback. The LTFT are the averages of the STFTs.
Yes, I understand the relationship between the O2 sensor, STFT and LTFT. The O2 sensor (narrowband AFR) fluctuates just as much as the STFTs trying to maintain 14.7 AFR. Not good for tunning.
Think of it this way, your car is tuned and happily driving at 14.7 when all of a sudden you suck a small baby into your intake. The ECU sees the O2 sensor voltage go way high and starts pulling fuel to keep 14.7 AFR. Not much air getting past the baby so your STFTs might be -15 or so. Now being that the STFTs can't adjust fast enough being choked down to -15 it applies a negative OFFSET (LTFT) and starts back at 0.
lol..
a small baby..lol. Okay, alright, I must compose myself...lol
There is a difference in the way our O2 sensor voltage and STFT calculate AFR. If you see a -15 (negative anything) STFT that is an indication of a rich condition becasue the ECU is taking fuel away to get 14.7 AFR. If you see a spike in the O2 sensor voltage, that is an indication of a rich condition and a valley indicates a lean condition. The LTFT offest will not be a negative, it will be positive. That is an indication of a lean condition or the STFT pulling fuel, not adding it.
Ok, I'm tired and being silly, good night.
Goodnight, I'm going back to celabrate the Saints masscare of the Colts!
I'll check in tomorrow to see what else I can learn!
