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Thread: Boost drifting downward

  1. #1
    Supporting Member II Turbo Mopar Contributor jeff1234's Avatar
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    Boost drifting downward

    I was studying my most recent mpscan plot and noticed that above 4000 rpm boost was dropping while rpm continued to rise. It wasn't much, about a pound of boost over time. Is this a pressure leak somewhere or is there some other cause.
    Thanx
    The only substitute for cubic inches is cubic dollars, how fast can you afford to go?

  2. #2
    turbo addict
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    Re: Boost drifting downward

    What is the setup of the car? There's a lot of things that can cause a dropping boost curve.

  3. #3
    Supporting Member II Turbo Mopar Contributor jeff1234's Avatar
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    Re: Boost drifting downward

    What specifically do you want to know?
    The only substitute for cubic inches is cubic dollars, how fast can you afford to go?

  4. #4
    Boost, it's what's for dinner... Turbo Mopar Staff Aries_Turbo's Avatar
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    Re: Boost drifting downward

    a manual controller will spike and then level out.

    Brian

    Quote Originally Posted by turbovanman
    This one is easy, I have myself to blame, I rush things, don't pay attention to gauges when I should, change to much stuff at once then expect miracles, the list is endless.

  5. #5
    Mitsu booster
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    Boost drifting downward

    Definitely need more info on the setup of the car; what engine, turbo setup, intake/exhaust manifolds, downpipe/exhaust, hows boost controlled, ecu type, etc..

    Reason for needing this info is some setups just don’t flow enough at higher rpms and will cause this, or it could be part of boost controller, etc..

    Sent from my iPhone using Tapatalk

  6. #6
    turbo addict
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    Re: Boost drifting downward

    ^^This

  7. #7
    Supporting Member II Turbo Mopar Contributor jeff1234's Avatar
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    Re: Boost drifting downward

    I do have a manual boost controller, im sure that is what is happening.

    - - - Updated - - -

    Reaper. Thanks for your response.
    The only substitute for cubic inches is cubic dollars, how fast can you afford to go?

  8. #8
    Super Moderator Turbo Mopar Staff contraption22's Avatar
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    Re: Boost drifting downward

    Could be a few reasons for that. One of the more common reasons is that exhaust backpressure overcomes the wastegate as RPM rises. If this is the issue, you can add some wastegate spring tension and that can help.
    Mike Marra
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  9. #9
    turbo addict
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    Re: Boost drifting downward

    Yes, exhaust backpressure is most likely going to be a major contributor given what we know.

  10. #10
    Supporting Member II Turbo Mopar Contributor jeff1234's Avatar
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    Re: Boost drifting downward

    That is interesting, if I have to get the wastegate solenoid off to put a spring on it somehow, that could be a problem. I can see where this could be a tuning problem if the boost spikes into detonation range and then drops back a bit.
    The only substitute for cubic inches is cubic dollars, how fast can you afford to go?

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