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Thread: Changing VE display

  1. #1
    Tuner in Training Poncho Dan's Avatar
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    Changing VE display

    Pardon my noob-ish question, but how do I display my VE as a percentage? Here's a picture to show what I'm talking about.



    I don't understand where the 4 digit numbers are coming from.

    Thanks.

    Poncho Dan

  2. #2
    Senior Tuner 5_Liter_Eater's Avatar
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    They don't need to be a percentage. Think of them as airflow. You log your AFR error or fuel trims and plot them against the VE table and then apply the percentage of error to the cells. Just like you would with a gen 3 VE table which is more like what you're used to seeing.
    Bill Winters

    Former owner/builder/tuner of the FarmVette
    Out of the LSx tuning game

  3. #3
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    Quote Originally Posted by Poncho Dan View Post
    Pardon my noob-ish question, but how do I display my VE as a percentage? Here's a picture to show what I'm talking about.



    I don't understand where the 4 digit numbers are coming from.

    Thanks.

    Poncho Dan
    The numbers are what are often termed GM VE. They are directly related to VE %. If you search on here for Marcin or "redhardsupra" he has a blog with some papers he has published that go into the details and the formula to convert GM VE to % VE.

  4. #4
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    here's the simple version:
    GMVE=VE*VOL/R

    VE is the traditional Volumetric Efficiency
    VOL is the cylinder volume
    R is a chemical constant

    Since chemical constants are ...umm... constant, and cylinder volume doesn't really change during engine's regular operation, recalculating the whole VOL/R bit is really repetitious and doesn't change, so they saved some ECU's operations by integrating it all together. Another interesting side effect is that this form of VE tells you how much airmass you'd have at given pressure and temperature. This is why i like to call it 'potential airmass' or 'normalized VE.'

  5. #5
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    Well that made the answer to the question pretty easy .

    Thanks Marcin!

    Poncho dan take a look at the link in Marcin's post. His papers make really interesting reads and they are the ONLY items of their nature generally available anywhere. Period.

  6. #6
    Tuner in Training Poncho Dan's Avatar
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    Thanks a ton, good reading.