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Thread: Primary VE table adjustment not making sense...

  1. #1
    Tuner in Training
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    Primary VE table adjustment not making sense...

    Ive gone on a couple drive now to collect data in the VCM scanner and im starting to get confused. I've flashed the pcm a couple times and my Cobalt SSSC is starting to run better, but it seems that the 3d view of the primary ve table is looking strange. Im getting extremly high value during low rpm ranges. I have aem wideband 02 sensor, and it reads around a 15-17 afr at idle/low rpm ranges. When i load data in my histograms though i am getting percentages of 20-30% at low rpms. Since the numers are positive, they are increasing the value in the primary ve table in the VCM editor. This is consistantly happening every scan, and I cant seem to figure out why. If the wideband is reading afr value of 15-17; then it should try to decrease this by logging negative values in my histogram at low rpm ranges correct?

    I have attached two screenshots to show what I am talking about. Any help or thoughts would be appreciated.

    VCM Scanner Screenshot.jpg

    VCM Editor Screenshot.jpg

  2. #2
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    Try disabling short and long fuel trims. Then reset fuel trims. Start over with ve tuning.

    Get in the habit of resetting trims for every flash.

  3. #3
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    If you disable the LTFT and STFT, then won't resetting them defeat the purpose since they are disabled?

  4. #4
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    No. Disabling them stops them from learning but it doesn't clear the data that they have already learned. So if you disable them and they currently have a 5% lean data value, they will continue to apply that value. So every time you scan, make changes, then flash that tune, it will then apply another 5%. This may be what's happening to you.

  5. #5
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    Your table looks terrible. I would go back to the original table/file and start over.

  6. #6
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    okay so that's what ill probably do, is go back to the original and start fresh there.

    The way ive been doing so far is, I created a custom histogram with my wideband sensor and made a formula to change the value into a percentage. Then I take those numbers and copy the histogram. Last, I have been going to the primary VE afterwards and past specialing with the multiply by % function. So just want to clarify so I understand properly; clearing out the LTFT and STFT data will work with the way I've been tuning right?

  7. #7
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    I think you've got it.

  8. #8
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    okay. I was looking in the hp tuner software, and trying to figure out where to go to clear the data. Where should I be looking to do this? Sorry if it seems like im not putting forth the effort, just getting a little frustrated since my data ive collected is kind of useless at this point.

  9. #9
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    No worries, it's under the VCM Controls icon in the Fuel tab.

    VCM.jpg

  10. #10
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    okay I found it. only problem is it not clickable. Is it because I am not plugged into the car at the moment?

  11. #11
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    Yes, you need to start logging first.

  12. #12
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    Thanks for the help

  13. #13
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    np, hope this helps you out.

    Are you following a guide for tuning?

  14. #14
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    yeah ive got a procedure that someone has been helping me with.

    Basically the way ive been doing it so far,

    is i changed values in the editor to eleminate as many variables as possible so i can get a good VE table set up. Then as far as the tuning process goes, i created a custom pid for my AEM Uego wideband, and set it up in a custom histogram. The histogram is plotting wideband afr as a percentage from the formula I entered. After collecting data from a drive in the scanner, i am copying the values obtain in the histogram into the Ve table by pasting them from the option called multiply by %. Then just repeating this over and over. This is my first time tuning, so im still really green when it come to understanding how everything works in conjunction with everything else. My main thing is ya i want to get my car tuned, but i want to understand everything as much as i can so i am not just blindly tuning.

  15. #15
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    Once you get close, switch to multiply by % half. It will help with over compensation.

    Good luck!

  16. #16
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    I have been trying to tune my VE table as well. With some strange problems too. I can't seem to get my VE table close. I started out my table was realy lean. Was in the 25% error. Had done so many logs doing this got frustrated. Had to put my original tune back in and take 5. Cobalt SS/SC 2005. Going to start over when I get back from vacation.

  17. #17
    Senior Tuner cobaltssoverbooster's Avatar
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    its 150 times easier when you convert to regulated return assembly
    2000 Ford Mustang - Top Sportsman

  18. #18
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    I would look into using some filters in your histogram when logging too. I have been experimenting with them myself. I am going through the same procedure right now with mine. Also make sure you don't have an offset in what your wideband is reading and what the scanner is seeing. I just happened to notice mine was off a little bit. I have the same identical setup with the AEM wideband. My gauge reads 14.9 while my scanner shows 15.1. I guess this is a common problem with grounding. My hptuner box is grounded to the same ground as the scanner. If yours is not I would do it. Maybe this will help clean up some of your errors.