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Thread: Fuel trims in Lean Cruise

  1. #1
    Lifetime Member Gregs's Avatar
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    Sep 2008

    Default Fuel trims in Lean Cruise

    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.

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    03 Silverado 5.3 ECSB 4x4 Z71
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  2. #2
    Lifetime Member 5.7ute's Avatar
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    Oct 2006


    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.
    The Tremor at AIR

  3. #3
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    Aug 2010


    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.


  4. #4
    Lifetime Member Chevy366's Avatar
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    Oct 2006


    My observations is the LC uses it own tables and LTFT has no impact on it .
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    Dinosaurs and Plants gave their lives so that we may drive , long live fossil fuel .

  5. #5
    Lifetime Member EagleMark's Avatar
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    Dec 2010


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

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