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Thread: 2007 Grand Prix Boost Limit

  1. #1
    Potential Tuner
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    Jul 2012
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    2007 Grand Prix Boost Limit

    Installed new 42lb injectors, bigger maf, and 1.9 ratio rockers and now whenever I go WOT I noticed that my boost goes down after about 4k rpm
    I get a solid 160+kpa that increases with rpm up to 4k then it feels like the pcm is closing the throttle body, I get a steady 140kpa up until it shifts.
    Anyone else ever had this issue?

    Current mods are headers, 1.9rr, IC, Water Meth, LQ4 MAF, 42lb injectors, 2.9" pulley

    I have looked at every TM setting, and I cant for the life of me figure out why it is commanding the throttle body to close

    I can post the log and tune if needed.

    I have also done a lot of searching and cant find anyone else with this issue.

    Would a crank position relearn do anything..? idk..

  2. #2
    Tuning Addict 5FDP's Avatar
    Join Date
    May 2012
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    Rogers, MN
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    13,533
    Is it actually closing?

    Are you able to log the channels to see what the blade is doing?

    You could have belt slips as well with that tiny pulley.
    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
    Potential Tuner
    Join Date
    Jul 2012
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    I'll grab a log with the throttle blade position. I do have a belt wrap kit as well so I'm currently ruling out belt slip until I can confirm the tb closing or not.