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Thread: Calc.MAFT: correcting VE and calculating MAF (in single log) --> reverse of Calc.VET

  1. #11
    Lifetime Member swingtan's Avatar
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    A quick note for the E38....

    I tried this some time ago with the E38, but we are missing the DYNAIRTEMP PID. I found you can get get very close with the following though....

    "({SAE.RPM}/120)*({E38.APCYL_DMA}*8)"

    This uses the ECM's existing Air/Cylinder figure which should factor in the air temp corrections. I'd think that the LS1 controller would be able to use a similar equation.

    Simon.


    I use it quite a lot to cross reference the VE table and the MAF and it helps point out things like reverberation.

  2. #12
    Joe (Moderator) joecar's Avatar
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    Quote Originally Posted by swingtan View Post
    A quick note for the E38....

    I tried this some time ago with the E38, but we are missing the DYNAIRTEMP PID. I found you can get get very close with the following though....

    "({SAE.RPM}/120)*({E38.APCYL_DMA}*8)"

    This uses the ECM's existing Air/Cylinder figure which should factor in the air temp corrections. I'd think that the LS1 controller would be able to use a similar equation.

    Simon.


    I use it quite a lot to cross reference the VE table and the MAF and it helps point out things like reverberation.
    Simon, good point.

    E38.APCYL_DMA is the ECM/PCM computation of VE[g*K/kPa]/DAT[K]*MAP[kPa], and probably includes some internal adjustments/corrections.

    LS1B equivalents of this are GM.DYNCYLAIR and GM.DYNCYLAIR_DMA.

    LS1B also computes the equivalent airflow GM.DYNAIR, we could simply use this diectly, i.e. MAF = {GM.DYNAIR}.

    We should probably experimentally log/calculate the following to see how they compare:
    MAF1 = {GM.VETABLE_DMA.VE}/{CALC.DAT.K}*{SAE.MAP.kPa}*{SAE.RPM}/15
    MAF2 = {GM.DYNCYLAIR_DMA}*{SAE.RPM}/15
    MAF3 = {GM.DYNAIR}

  3. #13
    Joe (Moderator) joecar's Avatar
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    Here's a calc_pids.txt file we can use to compare MAF1, MAF2, MAF3.
    Attached Files Attached Files

  4. #14
    Joe (Moderator) joecar's Avatar
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    Shawn,

    {GM.DYNAIRTMP_DMA.C}+273.15 now appears in too many calcpids, so it may be simpler to give it its own calc pid, see CLC-00-273.

  5. #15
    Joe (Moderator) joecar's Avatar
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    Quote Originally Posted by joecar View Post
    ...

    LS1B equivalents of this are GM.DYNCYLAIR and GM.DYNCYLAIR_DMA.

    LS1B also computes the equivalent airflow GM.DYNAIR, we could simply use this diectly, i.e. MAF = {GM.DYNAIR}.

    ...
    It seems that possibly the PCM may be including temperature adjustment/correction/modeling in these...

  6. #16
    Lifetime Member swingtan's Avatar
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    Oh, I just thought of something! If E38.APCYL_DMA is "VE[g*K/kPa]/DAT[K]*MAP[kPa]", then we should be able to reverse the equation to create a calc-pid for the actual charge temp.

    RE: comparing the tables, I've done this in the E38....

    Green=MAF Airflow.
    Turquoise=ECM Calculated Airflow (AIRPERSEC)
    Purple=Calc PID based off DYNCYLAIR and RPM.

    Click image for larger version. 

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    A closeup of the airflow after the first big throttle close.

    Click image for larger version. 

Name:	Air_Flow-Comparisons_01.jpg 
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ID:	10923

    Again, it's E38 based but the theory should hold true for LS1 as well.

    Simon.

  7. #17
    Joe (Moderator) joecar's Avatar
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    Simon, that's a very good observation, good insight

  8. #18
    R.I.P Shawn, 1956-2011 WeathermanShawn's Avatar
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    So the infamous SD Vs MAF Airflow Correction could be expressed (g/cyl) as:

    GM.DYNCYLAIR.DMA-GM.CYLAIR.DMA/GM.DYNCYLAIR.DMA X 100 (%)...???
    2002 Black Camaro Z-28 M6 Hardtop 11.0:1CR 425HP/410TQ SAE (400TQ@3500RPM)
    200cc Heads, 228/232 110+2 Cam, 1 3/4" LT's w/catts, GMMG, Koni Shocks, Hotchkis Springs, 35/21 Sways, 17" ZR1's, 3.90 Gears Roadrunner PCM LM-2 Serial Wideband
    EFILive Closed-Loop MAF/SD Hybrid Tune..


  9. #19
    Lifetime Member Mr. P.'s Avatar
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    There was no working or tuning on the truck last night - we had several rounds of quarter to ping-pong sized hail last night and thunderstorms here in Plano. :( So no log file to contribute this morning, sorry.

    Mr. P.
    2003 Silverado SS, with Novi-1500 "CAI mod"
    EFILive V 7.5 COS-3 (OLSD, for now!)

  10. #20
    Joe (Moderator) joecar's Avatar
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    Quote Originally Posted by WeathermanShawn View Post
    So the infamous SD Vs MAF Airflow Correction could be expressed (g/cyl) as:

    (GM.DYNCYLAIR.DMA-GM.CYLAIR.DMA)/GM.DYNCYLAIR.DMA X 100 (%)...???
    Yes, correct (corrects MAF table from VE table):
    (GM.DYNCYLAIR.DMA-GM.CYLAIR.DMA) /GM.DYNCYLAIR.DMA *100[%]

    Or like this (corrects VE from MAF table):
    (GM.CYLAIR.DMA-GM.DYNCYLAIR.DMA) /GM.CYLAIR.DMA *100[%]

    Those would give the correction errors percentages.

    Shawn, good observation... this presents a very interesting shortcut.
    Last edited by joecar; May 25th, 2011 at 03:35 AM.

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