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Thread: 1999 ls1 pcm sd tune fans turning on before commanded temp

  1. #1
    Tuner in Training
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    Jun 2008
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    1999 ls1 pcm sd tune fans turning on before commanded temp

    I am in the mists of getting the VE tables in order and one thing I have noticed is fan 1 and 2 is coming on at like 100* for what seems like the minimum duration of fan operation in the tune. This also irritates the car as the additional load from the alternator on the cold engine almost makes it die, but doesn't. This will affect me tuning (trying to tune) the Base Running Airflow table if I forget to manually disable fan 1 and 2 operation. Is this normal for SD tuning?
    Attached the tune file.
    Have not tuned the MAF or Base Running airflow yet either as the VE needs to be close ironed out. I have only been working on idle to 2000 rpm after realizing my engine builder set the cam an additional 4 degrease advance . I wound up having to peel it apart and time it dot to dot. I didn't degree it as I didn't have the tools to do so.

    If I am missing anything, tune setting wise for the fans, please let me know.
    thanks!
    Attached Files Attached Files

  2. #2
    Tuning Addict 5FDP's Avatar
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    May 2012
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    I wouldn't think it would have anything to do with not having the MAF dtc's set right for speed density tuning but they should be fail on first error.

    The secondary VE looks crazy though, those are some massive numbers you have in there. Like numbers not even possible to see on the NA motor. Not sure how you ended up with numbers all the way into the 140's. Changes should be made to both tables though.

    Past that I didn't see a reason for why the fans would just jump on for no reason.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  3. #3
    Tuner in Training
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    Jun 2008
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    Not sure on the ve table numbers but I've only gotten to 2k cleaned up. I'm just working from the mail order tune.. I gave up on the tuner, but in the end it wasn't his fault, engine builder advanced the cam 4*.
    Thanks for the reply