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Thread: MAF [lb/min] Pegged, But Period Keeps Decreasing, Air Load Rising?

  1. #21
    Senior Tuner CCS86's Avatar
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    Quick update:

    The real issue here was insufficient fuel supply. The dual DW400s were not enough, the hat configuration was not ideal, nor was the tee splitter in front of the rails.

    Now with a better hat, triple pumps, and wye splitter; all the MAF curve increases are backing out.

    I think the dead give away here was that when it started going lean, the injector PW was rising relative to air load. Once the boost flattens out, your PW should as well. Fuel flow rate obviously rises with RPM, but PW should stay locked to trapped airmass.

    I'll post an after log soon.

  2. #22
    Senior Tuner veeefour's Avatar
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    Quote Originally Posted by CCS86 View Post
    Quick update:

    The real issue here was insufficient fuel supply. The dual DW400s were not enough, the hat configuration was not ideal, nor was the tee splitter in front of the rails.

    Now with a better hat, triple pumps, and wye splitter; all the MAF curve increases are backing out.

    I think the dead give away here was that when it started going lean, the injector PW was rising relative to air load. Once the boost flattens out, your PW should as well. Fuel flow rate obviously rises with RPM, but PW should stay locked to trapped airmass.

    I'll post an after log soon.
    what i told you?

  3. #23
    Senior Tuner veeefour's Avatar
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    Quote Originally Posted by decipha View Post
    thats the maixmum airmass limit of the ecu

    you have to scale the tune back
    Not true actually, ECU can keep way higher, that is a limit of ODB bit rate...

  4. #24
    Senior Tuner CCS86's Avatar
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    Quote Originally Posted by veeefour View Post
    what i told you?

    Yes, shortly after I said that I thought fuel pressure was dropping, you also suggested the fuel system was falling behind. Both our suspicions were correct.


    Quote Originally Posted by veeefour View Post
    Not true actually, ECU can keep way higher, that is a limit of ODB bit rate...

    I don't think it is a bit "rate" issue, but rather a variable type issue. Either way, it's a display issue, not affecting the important calculations.
    Last edited by CCS86; 05-17-2022 at 08:50 PM.

  5. #25
    Senior Tuner veeefour's Avatar
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    Quote Originally Posted by CCS86 View Post
    Yes, shortly after I said that I thought fuel pressure was dropping, you also suggested the fuel system was falling behind. Both our suspicions we're correct.
    I don't think it is a bit "rate" issue, but rather a variable type issue. Either way, it's a display issue, not affecting the important calculations.
    86lb is a SAE PID limit for airflow - fo sho m8...

  6. #26
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    You can only count so high, using 16, 1's or 0's.

    16 bit channel display limit. Grams per second you'll see the number 655.35 or whatever 2^16 is.

  7. #27
    Senior Tuner CCS86's Avatar
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    Quick update:

    The primary issue was definitely a lack of fuel supply, and the PCM is perfectly capable of calculating and fueling without any "scaling" tricks.

    We aren't done yet, since there are some tensioner issues to sort out. But, we are very much back on track and I am slowly pulling out the MAF curve corrections entered to compensate for the undersized fuel pumps.

    Image 35.jpg