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Thread: MAF calibration

  1. #1
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    Default MAF calibration

    Out of interest, what are the average adjustments being needed when calibrating the MAF, for example I am seeing roughly -11% across the Hz range, is this normal?

    I'm starting to suspect the injectors that came with the L76 complete intake manifold are smaller the 42lb hr? I use LS3/LS7 injector tables. Its an LS2.

    I should check the fuel pressure too
    Last edited by Gelf VXR; July 18th, 2017 at 04:13 AM.

  2. #2
    Joe (Moderator) joecar's Avatar
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    I sometimes see 10-15%.

  3. #3
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    Its odd this doesn't get highlighted that much, its quite a drop, is the factory calibrated MAF really that far off, or is it the injector data?

    Strange I did find the EROD 2010 LS7 tune file has much lower injector flow base, looks close to stock LS2 injector flow base data actually.

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    Quote Originally Posted by Gelf VXR View Post
    Its odd this doesn't get highlighted that much, its quite a drop, is the factory calibrated MAF really that far off, or is it the injector data?
    Most likely the injector data.

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    Logic suggests that the MAF and base injector flow rate should be correct from the factory, after all the development they have done, any issue with the fuel trims must be with the hardware or the rest of the tune, imho we should leave both the MAF and injector flow as stock as load, traction control, spark, MPG etc. are dependent on these calibrations. It seems that GM make corrections across different platforms to the B1210 MANVAC/VOLTS calibration, when I tried different B1210 map from the one I was using the trims trended towards zero from quite negative.

    I'm logging volts and baro/MANVAC to make changes to B1210 only, although you can not apply BEN or trims directly, I'm trying scaling this map up or down to achieve zero trims on this map. And I'm calibrating VE dynair to stock MAF airflow. See how I get on.
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  6. #6
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    Has the MaF been moved at all? That can affect the measured airflow.
    00 Silverado Z71, LQ9 w/ LS3 heads, BTR cam, Whipple 2.9@8#, 4l80E

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    Quote Originally Posted by LastCall View Post
    Has the MaF been moved at all? That can affect the measured airflow.
    No, it's a stock intake and filter


    Sent from my iPhone using Tapatalk

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    Lifetime Member 5.7ute's Avatar
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    Back in 2009 I came up with a method of calculating offsets assuming the airmass calculation was correct. Never tried it though. I have added it to the bottom of this post to see if my thoughts might help.


    From what I have seen so far in the IBPW calculation I believe we can dial in the voltage offset adder with a known good tune on stock injectors. As long as our IFR table is correct for the injector, and we are commanding a decent pulsewidth away from the default pulsewidth & small pulse adjust tables where IFR is linear.
    First we make a calc. pid called CALC.IPW
    CALC.IPW = ({GM.CYLAIR_DMA}/{GM.AFR}/{GM.INJFLOW})*1000 for a maf set up or
    CALC.IPW = ({GM.DYNCYLAIR_DMA}/{GM.AFR}/{GM.INJFLOW})*1000 for speed density.
    If GM.INJFLOW is not supported like on our holden platform a custom pid using the lookup() function can be used.
    This gives us the part of the pulsewidth that the PCM calculates for fuel minus the offsets & adders. (This pid is also used for other calculations I have been working on so I have kept it seperate from the rest of the equation.)
    Then we need to make the pid to calculate the error in the offset. If the offset is too small for the injector, not enough pulsewidth is added & a lean condition will result. The necessary amount to be added is easily calculated by the equation
    correction= CALC.IPW -(({GM.CYLAIR_DMA}/{WO2.AFR}/{GM.INJFLOW})*1000) .
    This correction can then be added to the {B3701} table.
    Note: since we are assuming that cylinder airmass is already correct, this method will not work unless the VE table/ maf curve were tuned previously with a known, accurate set of values.
    The Tremor at AIR

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    Quote Originally Posted by Gelf VXR View Post
    Logic suggests that the MAF and base injector flow rate should be correct from the factory
    Good luck with that.

    Quote Originally Posted by Gelf VXR View Post
    when I tried different B1210 map from the one I was using the trims trended towards zero from quite negative.
    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? If your actual fueling in PE doesn't match the commanded fueling for PE, then you've probably adjusted the wrong table.

  10. #10
    Lifetime Member Chevy366's Avatar
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    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.
    2005 1500 HD , Custom OS3 SD tune .
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    Dinosaurs and Plants gave their lives so that we may drive , long live fossil fuel .

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