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Thread: MAF Tune Struggle

  1. #1
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    MAF Tune Struggle

    Hello,

    Been trying to tune the MAF on my car but keep winding up with a lot of spiking numbers. The curve overall tends to take on more of an s-shape than the exponential curve that seems to be what it should look like.

    I've attached my last data log, and the last tune and data log (both numbered 6) and the follow on update I made based on the data log (7_1).

    Car is an 00, I updated to the 01-02 OS. Mods are Torquer V2 cam, PRC225 heads, Fast 92/92 intake and TB, Long Tubes, and true duals.

    Am I missing something?

    Thanks in advance.
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  2. #2
    Tuning Addict 5FDP's Avatar
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    Your commanded AFR is never the same, so that is not helping. You must have the open loop EQ ratio at 1.00 for all cells at operating temp. It can not move from 1.00 to 1.01 or 1.04, that is throwing off your MAF tuning.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  3. #3
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    Thank you. I set that table to 1.00 across the board and will try another run. Thank you.

  4. #4
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    Thanks again for the help. I changed the values in the open loop EQ ratio table to 1.0. Also after some reading, and some videos, I also changed the values for HI/LO RPM and MAP threshold to 100 RPM/0kPa under steady state in the dynamic airflow tab. Four runs seem to all have A/F values that make more sense, but there are still a lot of points in the MAF curve that don't follow the curve well. The plot also seems to keep forming a "bump" at the 8000 Hz mark. Any Jaggedness should be completely smoothed?

    Could IATs skew the curve? It's mid-80's to 90's here lately, and the sensor seems to heat soak when sitting and after shutting down between runs

    I've attached my 4th run tune file, the associated log, and the update I saved as my 5th.

    Thanks.
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  5. #5
    Tuning Addict 5FDP's Avatar
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    You are bumping in and out of PE right around 8,000hz.

    I would change your PE settings so it's not entering PE at such a low throttle percentage in the higher rpm. You should be just doing normal driving with medium throttle to get most of the MAF curve done. Make sure to hand smooth the curve and use the smoothing functions to stop the dips and jagged lines. Once the majority of the MAF is done then I'd lower the PE stuff back down for wide open throttle stuff.

    Make your PE one value as well to make tuning that much easier as well. The rise and fall of commanded fueling makes it hard to dial things in. If you are able to dial it in on once specific air fuel ratio it should be pretty close to spot on if you change it to a different value.

    Also your timing tables are flipped flopped. Your low octane table has more timing in it that your high octane table. That is not good if there is knock because the low octane timing would try to add more timing instead of remove it. Aim for around mid 20's and not 30-31 degrees.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  6. #6
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    Thanks for the tips. I can see where that's happening now. I changed the minimum MAP value for PE enable to 94 kPa (13.7 psi), which seems to be the value it hits at around 75-80% throttle in the data logs. I also changed the PE table to all one value as well (1.177), and will correct the spark table. I'll take her out tomorrow and see where I'm at. Thanks again for the help.

  7. #7
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    Thanks again for all your input, I seem to be on the right track now, and seeing improvements between logs in most areas. I'm also seeing a pretty significant lean spot from around 6750Hz up to around 9000Hz. It seemed to get worse between run 6 and run 7 (attached).

    My next question is related to the "bump" I brought up previously. It has basically shifted to the right after I changed the PE entrance criteria. I am now seeing severe dips and spikes around 9000-9500 Hz which I see now is causing this "bump" due to the fact that PE is starting to kick in. Should I once again change the entrance MAP value (thinking 14.2), or is this safe? From what I read, PE should be left enabled to prevent leaning out under these conditions, but is continuing to bump up the entrance value just as risky as disabling? Is there another method I should be using?

    Thanks
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