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Thread: Confused about MAF

  1. #1
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    Default Confused about MAF

    Can someone help clarify my question about MAF changes for me?

    Ive logged average MAF airflow (g/s) vs RPM as well as CALC.SELEBEN vs RPM. My logged average MAF aiflow g/s is considerably different than my calculated MAF table after factoring in my CALC.SELEBEN. Ive eliminated TP% changes and temps below 178* on both by way of the map filters.

    What is the main difference in what Im looking at?

    Why are the 2 different?

    Im just trying to get a better understanding for each.

  2. #2
    Joe (Moderator) joecar's Avatar
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    How are you calculating MAF (from VE...?)...? Show me your calculation.


    Which PCM OS is this...?

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  4. #4
    Joe (Moderator) joecar's Avatar
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    You didn't log GM.VETABLE_DMA...

    the CALC.MAFT calculation starts with VETABLE_DMA, applies the SELBEN correction, and calculates a MAF table from that.
    Last edited by joecar; April 18th, 2012 at 09:55 AM.

  5. #5
    Joe (Moderator) joecar's Avatar
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    Posts some pics of:
    - your VE B0101 table,
    - your VE BEN map,
    - your CALC.MAFT map,

    for each map, make sure to checkmark the Units box on each of the Data/Row/Col tabs.

  6. #6
    Joe (Moderator) joecar's Avatar
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    The uncorrected calculated MAF is defined as "{GM.VETABLE_DMA.VE}/{CALC.DAT.K}*{SAE.RPM}*{SAE.MAP.kPa}/15"...

    the CALC.MAFT calculation is the SELBEN correction of that...


    is CALC.MAFT what you're using as your MAF calculation...? If so, then you didn't have VETABLE_DMA in your log.

  7. #7
    Joe (Moderator) joecar's Avatar
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    Something majorly wrong with your calc_pids.txt... I'm fixing it...



    so on your analog voltage input AD2 you have the pin shorted to ground, is that correct...?

  8. #8
    Joe (Moderator) joecar's Avatar
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    Quote Originally Posted by wcj View Post
    Os - 12221588
    DYNAIRTMP_DMA is defined for that OS... I see it in your log.

    What about VETABLE_DMA, does it show up when you validate pids...?


    What year/model/vehicle is this in...?

  9. #9
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    You'll have to forgive me for a bit. Been a long day at work so it will take me some time to shift my brain to efi.

    I completely forgot I switched OS so Im sure my pids reflects that. I have a 2003 Corvette Coupe.

    AD2 is not shorted. This is what my analog outputs look like.

    Click image for larger version. 

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ID:	12948

    DYNAIRTMP_DMA is logged and is a valid for me.

    VETABLE_DMA is a valid pid. I just relogged my drive home with it enabled, but I havent built any maps with it.

    MAPS-
    Click image for larger version. 

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ID:	12949
    Click image for larger version. 

Name:	VEBEN.jpg 
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ID:	12950

    VE Table-
    Click image for larger version. 

Name:	b0101.jpg 
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ID:	12951

    Im also attaching the log from my drive home.

    Log_0028.efi

  10. #10
    Joe (Moderator) joecar's Avatar
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    No worries


    Your calc_pids.txt had some serious problems (calculating out-of-sequence, interfering with predefined pids, other stuff) which I fixed...


    VETABLE_DMA is used for the Calc.MAFT calculation.


    Ok, your AD2 input is not connected to ground (for voltage offset correction to AD1), I'll edit out the offset correction...


    Try the attached calc_pids.txt file, copy to the User Configuration folder, and then restart the scantool.
    Attached Files Attached Files
    Last edited by joecar; April 18th, 2012 at 12:28 PM.

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