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Thread: Boost Control CO2 Not Following

  1. #11
    Join Date
    Nov 2013
    Chicago IL


    From the looks of that picture, it looks like you just have too much "I" in the PID settings.
    It follows well, but it follows with big jumps up & down.

    Basically, "P" gets it there in large steps.
    "I" follows it once you are there in smaller steps.
    "D" slowly reduces or increases the I over time. (Use only in VERY SMALL amounts; one too many and it upsets the whole thing - especially if the "I" is already small to begin with.)

    When I tune Boost control, I start with just some shop air and program a button (transbrake works well) to be a small amount of dome pressure (like 5 psi).
    I set the boost control (use the boost vs time) to be a high number (like 25 psi).
    Then I toggle between the 2 as I work with the PID settings.

    Start with all at 0, bring the "P" up one at a time, until it comes close to the target boost (but does not overshoot) when you release the button.
    Then you can start adding "I" one or two at a time, until it comes up to the target without overshooting too much or to quickly.
    You will very rarely need the "D".

    It's better to have it be a little slow & slightly undershoot, than to overshoot & oscillate a bunch.
    Last edited by S2H; 12-24-2015 at 09:56 PM.
    Don't forget to check out progress on my Race Car:
    Project Blasphemy - 8.07 @ 171
    Low 8 Second Street Car

  2. #12


    Thanks Scott, Merry Christmas.

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