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Thread: torque priorities while tuning VTT

  1. #1
    Tuner in Training
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    torque priorities while tuning VTT

    I am trying to narrow down why my throttle is closing. So we have 3 torque PIDS that seem to be important. We have Peak engine trq, predicted engine trq, and engine trq.

    I have my peak engine trq tables set so that is always the highest value.

    So when adjusting your VTT, I assume you need your predicted trq higher than your engine trq also, correct?

    In the screen shot attached, with steady pedal position, my TB is closing from 100 to 50%, killing my boost. I notice in the logs that my predicted trq is way lower than my engine trq. I assume this is the cause of the TB closing. the throttle control source PID stays at torque for the pull.

    To fix that, I need to go into the VTT tables and bump them in the areas I am being limited at, correct?

    What are the current thoughts on dialing in the VTTs?

    Thanks!


    TB closing.png
    Last edited by str8dum1; 2 Weeks Ago at 10:55 AM.

  2. #2
    Tuner in Training Mbrowning's Avatar
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    I believe Russ Kemp commented on a post similar to this in the past. Believe it or not, the fix for the problem was leaving the vtt and torque tables alone. He also advised leaving the dd tables stock except for the 100% line. That line is maxed all the way across the rpm range. It's been a while since I read the post, but might be worth checking out.

  3. #3
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    Have you touched your VVE table at all? Put all your trq tables back to stock and work on your MAF and VVE. If they're in line, your throttle will stay open.
    2019 C7 ZO6 M7.

  4. #4
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    fueling within +/- 5% and still closing.

  5. #5
    I am experience something similar. I am out of town now, so won't be able to do more testing for about 2 weeks, but have some ideas for when I get back to it. But I have MAF and VVE pretty darn close and have throttle going to about 65-70% depending on conditions. Seems like it should be getting to ~84%. Something seems to be limiting. This is a 2017 Sierra 6.2 L86/8L90E

  6. #6
    Tuner in Training Mbrowning's Avatar
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    Still closing, but did you try returning the torque tables to stock?

  7. #7
    Tuner in Training Mbrowning's Avatar
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    giffincox, normally when the blade is wide open, PID will show 89% for some reason.

  8. #8
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    I ran into a similar issue while tuning a HCI LT1 on an engine dyno. When my predicted torque was less than delivered I would get throttle limiting. I reduced the areas in the VTT tables where throttle was limiting until predicted was in line with delivered TQ. I was then able to make WOT pulls without the throttle closing. Raising the VTT values made the issue worse.

  9. #9
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    Only time I had throttle closing was with heads/cam and full bolt on. Believe it or not the only way i could get the throttle to stay open was by lowering the VTT.

  10. #10
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    Quote Originally Posted by chuckk View Post
    Only time I had throttle closing was with heads/cam and full bolt on. Believe it or not the only way i could get the throttle to stay open was by lowering the VTT.
    Where is that table found?