What are S-trims
03-06-2003, 08:16 AM
#2
Re: What are S-trims Ltrims are Long term fuel trims (LTFT). S trims are short term fuel trims. Ltrms are cells in the pcm the engine reads from depending on conditions. Cells are arranged depending on MAP and RPM. So for a given RPM/ MAF range the pcm selects the appropriate cell.These cells are used, by the PCM, to determine base injector pulsewidth as it monitors and adjusts fuel to maintain 14.7 AFR.As operating conditions change the PCM can make adustments, + or - % ,to the base table within any given LTFT cell.
STFT is a short term adjusting cell that the PCM can look at and adjust (fine tune) the Injector Pulsewidth within any given LTFT cell. Adjustments are made as + or - % to base pulsewidth equation. If the STFT exceeds calibrated range the PCm will adjust the LTFT to attempt to bring STFT back within calibrated range (if it can't it sets a code).
STFT are lost each time the PCM powers down and therefore are zero each time the PCM boots up.This has major consequences in tuning stability.Sorry for the book....hope this helps some.
joel
<small>[ March 06, 2003, 09:55 AM: Message edited by: binksz06 ]</small>
STFT is a short term adjusting cell that the PCM can look at and adjust (fine tune) the Injector Pulsewidth within any given LTFT cell. Adjustments are made as + or - % to base pulsewidth equation. If the STFT exceeds calibrated range the PCm will adjust the LTFT to attempt to bring STFT back within calibrated range (if it can't it sets a code).
STFT are lost each time the PCM powers down and therefore are zero each time the PCM boots up.This has major consequences in tuning stability.Sorry for the book....hope this helps some.
joel
<small>[ March 06, 2003, 09:55 AM: Message edited by: binksz06 ]</small>