Fuel trims in Lean Cruise

[Gregs]

I had been seeing ltft showing up during lc and I wasn't sure if they were actually affecting the mixture or if the computer was just ignoring the fuel trims. Tonight I logged a stretch of road and attached are the logs. I filtered both logs and compared the bens of each log with each other. Let me know what you guys think. Its less than a 5% difference but to me it seems like there is a correlation.

in each log i started ate the startpoint and drove, then turned around and came back to the starting position.

12445

12446

[5.7ute]

LTFT should still show in the log, but since you are not in Closed loop for lean cruise the fuelling would not be affected by O2 sensor feedback.
I do not have Efilive on this computer, but will take the logs home to have a look.

[Taz]

Hi Greg,

Great idea for an experiment. As many already know, there are no STFT while in LC (logs will show 0) - the PCM runs in OL directly from the VE table. But your question - do the preexisting LTFT stored in the PCM memory impact (in anyway) on the final fueling while in LC - is not something I have ever looked into.

When the difference in the results are less than 5% from a road course test - it is difficult to infer causality. Someone with a chassis dyno and an inquisitive mind could probably settle this question.


Regards,
Taz

[Chevy366]

My observations is the LC uses it own tables and LTFT has no impact on it .

[EagleMark]

My Wide Band O2 sensor also shows no LTFT effect during Lean Cruise.