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Thread: MAF calibration

  1. #11
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    Quote Originally Posted by statesman View Post
    Lowering B1210 will lean out the fueling, but so will raising the IFR or lowering the MAF curve... so which of those tables really needs to be adjusted?.
    That was the point I was making, adjusting the MAF or base IFR will affect other calculations for load, TC, spark etc


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  2. #12
    Lifetime Member Chevy366's Avatar
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    All you are doing is moving a point on the scale, the calibration scale didn't change just the point on the scale within the calibration scale.
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  3. #13
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    Quote Originally Posted by Gelf VXR View Post
    That was the point I was making, adjusting the MAF or base IFR will affect other calculations for load, TC, spark etc
    No, only adjusting the MAF will alter those calculations. Adjusting the IFR will alter the amount of fuel supplied but will not alter the calculations for load, spark, etc.

  4. #14
    Joe (Moderator) joecar's Avatar
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    Quote Originally Posted by Chevy366 View Post
    I would think the MAF is a like a calibrated instrument, calibrated to detect a range of air flow derived from a static environment and known air flow rate values.
    The MAF table is like the VE table... the factory may or may have not spent sufficient resources on either, possibly depending on the vehicle.

  5. #15
    Joe (Moderator) joecar's Avatar
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    Quote Originally Posted by Gelf VXR View Post
    That was the point I was making, adjusting the MAF or base IFR will affect other calculations for load, TC, spark etc
    +1 what statesman said...

    IFR and OLFA and PE tables affect fueling only.

    MAF and VE affect airmass, load, spark, TC, torque calculations/lookups (and transmission line pressure calculation).


    Fueling and airmass/load are dealt with separately.

  6. #16
    Lifetime Member Chevy366's Avatar
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    Aren't MAF and VE based on a static air pump volume? Unless you alter that air pump volume in some way the MAF and VE remain the same since the air pump volume hasn't changed. If MAF and VE have such a drastic effect on other parameters maybe we should leave them alone. Then again, maybe all they do is gauge air pump volume.
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  7. #17
    Joe (Moderator) joecar's Avatar
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    Quote Originally Posted by Chevy366 View Post
    I would think the MAF is a like a calibrated instrument, calibrated to detect a range of air flow derived from a static environment and known air flow rate values.
    Quote Originally Posted by Chevy366 View Post
    Aren't MAF and VE based on a static air pump volume? Unless you alter that air pump volume in some way the MAF and VE remain the same since the air pump volume hasn't changed. If MAF and VE have such a drastic effect on other parameters maybe we should leave them alone. Then again, maybe all they do is gauge air pump volume.
    What I'm saying is that like any of the other tables, GM does not always calibrate the VE and/or MAF tables correctly and/or completely.

    i.e. don't trust MAF table as being gospel correct from the factory... use a wideband to check it, you will be surprised.
    Last edited by joecar; July 26th, 2017 at 08:26 PM.

  8. #18
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    Remember guys, GM has LTFT and STFTs for a reason, to compensate for variation. MAF and/or VE/VVE may be correct for 10 of their test engines, yet engine production, environment, and so forth all contribute to variation.

    You need to calibrate BOTH MAF and VE/VVE when tuning.
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  9. #19
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    Quote Originally Posted by joecar View Post
    +1 what statesman said...

    IFR and OLFA and PE tables affect fueling only.

    MAF and VE affect airmass, load, spark, TC, torque calculations/lookups (and transmission line pressure calculation).


    Fueling and airmass/load are dealt with separately.
    Yes I agree, as in what I said altering either the base IPW or MAF will have knock on affect on MPG calculations in case of IFR or load, spark and torque in case of MAF.

  10. #20
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    Default MAF calibration

    Quote Originally Posted by joecar View Post

    i.e. don't trust MAF table as being gospel correct from the factory... use a wideband to check it, you will be surprised.
    I wouldn't agree that the MAF is incorrect just because the WB indicates the AFR is not the same as commanded, the AFR is wrong for some reason, but we can calibrate the MAF to the inconsistency to achieve the commanded AFR, is this best practice thou?

    If we look at the terminology "fuel trims", the ECU trims the fuel not the MAF which leaves all the dependent calculations alone, adjust the MAF and those calcs might now be incorrect, however if as I am trying, tune the injector flow correction modifier table B1210 (and it does vary across platforms where as base IFR does not for the same injector), MAF airmass, load, spark, TC, torque calculations/lookups are unaffected
    Last edited by Gelf VXR; July 29th, 2017 at 08:42 PM.

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