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Thread: WOT PE issues due to Manifold Vacuum readings?

  1. #1
    Potential Tuner
    Join Date
    Jul 2013
    Posts
    5

    WOT PE issues due to Manifold Vacuum readings?

    Running the car on the dyno today, I saw some weirdness that I am hoping to get some help on. Specifically, commanded AFR's were fluctuating when the car should have been in PE and the timing was doing the same. Only thing I could find was that the manifold vacuum reading was switching from 9 to -128 kpa. Historically at WOT the manifold vac readings were solid -128kpa. The values seem to be fine everywhere except at WOT. I swapped out the sensor and it didn't make a difference so I am wondering if I am pegging it maybe given the boost is 20psi and it is not liking it. At any rate, logs, configs, and tune attached.

    I'm actually not even sure where the value for manifold vacuum is coming from given the car has a MAP, an SC inlet sensor, and a baro sensor which all seem to be reading fine. Is it a calculated parameter that has reached a threshold or something? I have stopped pushing it as a result so I'd like to figure it out so that I can finish and enjoy the car.

    In the 6th log the pull starts around frame 3400
    In the 7th log the pull starts around frame 2925.

    Thanks in advance!

    Lysholm E85 TFS BTR2 DDT_1-mixed maf-smooth after 4 pull.hpt
    2012 CTS-V-WB-Alc%-lambda VE.cfg
    6th full pull - 754hp.hpl
    7th full pull - 742hp.hpl

  2. #2
    Potential Tuner
    Join Date
    Jul 2013
    Posts
    5
    I think Dave Steck helped me out enough to look for what I need but if others have ideas, feel free to holler. The OS on the CTS-V is setup for 2.5 bar and I am flirting with the limit at WOT. I am going to try a few things and see if I can work around it.