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Thread: Maf sensor saturated

  1. #1
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    Maf sensor saturated

    Anybody know what the Driver demand limit source maf sensor saturated means?

    12 gt500


    Thanks

  2. #2
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    Sound like the maf has been exceeded? I have never heard of this but that's an educated best guess.

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    HPT Employee Eric@HPTuners's Avatar
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    Quote Originally Posted by curt@injected View Post
    Anybody know what the Driver demand limit source maf sensor saturated means?

    12 gt500


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    Yeah, you are nearing the limit of the MAF. Scale the period side of the curve so that it goes higher (numerically lower) and it should fix the issue.
    Eric Brooks
    HP Tuners, LLC

  4. #4
    Advanced Tuner bbrooks98's Avatar
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    Quote Originally Posted by Eric@HPTuners View Post
    Yeah, you are nearing the limit of the MAF. Scale the period side of the curve so that it goes higher (numerically lower) and it should fix the issue.
    I've just started running into this issue. Funny thing is prior to re-scaling the MAF to a lower period value like mentioned above it didn't seem to hit the MAF saturated Driver demand. It's too close to keep that way and I also wanted to get some head room for more boost in the future. Is there anything else to this i'm missing? An undefined parameter maybe?
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  5. #5
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    Engine diag.> airflow> Default period. I believe you need to make that number lower to prevent this limit.
    "We can never be right, we can only be sure that we are wrong"- feynman

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    if your MAF is Saturated is you load Maxed? Once the MAF is saturated it stays saturated and the MAF controls load unless your displacement scalar is really low. Volumetric efficiency is basically a question of how much air the engine displaces per revolution, not in total. If the air meter says you're moving 100 lb/min of air at 5000 RPM, you are effectively moving .02 lbs of air per revolution. If the air meter is pegged at our hypothetical 100 lb/min figure, unable to go any higher, and RPM increases to 6000, the computer would then think you are only moving .0167 lbs of air per revolution, which is a lower level of volumetric efficiency. Thus, calculated load decreases, and bad things happen because the PCM continues to inject fuel based on how many lb/min of air it thinks it's getting (going lean) and it runs timing values based on a lower calculated load (which could very well result in insanely excessive amounts of advance).

    Quick band aid way around it - either use fuel adders or if the processor doesn't have them available, add fuel at the pegged level in the base table, zero out all spark adders and lock the timing (and fuel if it's load controlled). But doing this you are giving up fuel control and it will end up being lean on cold/dense air days and rich on hot/thin air days.
    Last edited by mstang_man; 01-02-2017 at 10:34 AM.

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    Have you maximized the range of the MAF? I believe gt 500's don't have these switches MAF Limit Switch and Switch to enable MAF limit Calibration if so set those to 1. also, change default Period In Microseconds to 106.. Period is a timed event in the PCM. default is 1000 microseconds you can increase sample time by lowering this between 101--110 but always keep above 100. If you rescaled the MAF did you rescale Fuel Injector HI/LO Slopes, Injector Break Points, and Engine Displacement by the Scaling factor, example say 0.7 I cant look at the logs.

  8. #8
    Advanced Tuner bbrooks98's Avatar
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    I think Murfie nailed it in the post above. I had forgot about the MAF settings under engine diagnostics. Mine was set to a period limit of 90us which is right where the MAF period was bouncing around. I lowered it to 75us but haven't had a chance to re-test it since it's raining out here. What you're describing sounds like a way to re-scale to get around an airflow limit? It's only at roughly 62lbs/min. Its in a 3.5inch charge pipe which is whats making the MAF frequency so high. These Ford sensors look exactly like the LS3 sensors which go to 15000hz. Ford seems to top them out at 11111hz in the factory calibrations. I've heard they can be re-scaled to go a bit higher than the factory limits?

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    what I found strange is your MAF limit switch is disabled. It shouldn't be closing the throttle because of the default, but it might be.
    "We can never be right, we can only be sure that we are wrong"- feynman

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    Advanced Tuner 15PSI's Avatar
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    bbrooks98: I just sent you a PM.
    2012 Mustang GT with S/C
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  11. #11
    Advanced Tuner CCS86's Avatar
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    Hey guys, I just ran into this issue on a customer's car.

    He is running the same strategy as I am, with all the same MAF related settings, but at a lower boost. I have never seen this limit, but he is hitting it at a MAF period of 109. I have run mine to 103 and below with no limit.

    Any ideas?

    MAF settings.jpg


    Interestingly, the throttle stays open, despite having the MAF limit switch turned on. Also, the reported MAF rate continues to climb like normal.

    Is it possible that a dirty MAF element could cause an erratic signal and trigger this?
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    Last edited by CCS86; 4 Weeks Ago at 02:09 PM.

  12. #12
    Advanced Tuner CCS86's Avatar
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    No change after cleaning the MAF sensor.

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    You noticed the desired airmass hits the value in the top cell of that transfer right?

    Desired and actual should match or be very close to each other, for everything.
    "We can never be right, we can only be sure that we are wrong"- feynman

  14. #14
    Advanced Tuner CCS86's Avatar
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    I did notice that desired was very high relative to actual airflow. That sort of makes sense that it both desired and actual flow could trip the limit.

    I think you nailed it murphie, the limit triggers right when desired hits the top of the table. Thank you for the insight!

  15. #15
    Advanced Tuner CCS86's Avatar
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    Well, as much as that made sense, here is a new log showing the limit getting tripped at a much lower desired MAF rate. Well short of the table max...

    Before this log was taken, I did change the "default MAF period" from 90.33 to 102... which on closer inspection does match up with the new limit.

    Going to test the theory now.
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    Last edited by CCS86; 4 Weeks Ago at 08:41 AM.

  16. #16
    HPT Employee Eric@HPTuners's Avatar
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    This will keep the TB from closing when this limit is hit.
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    Eric Brooks
    HP Tuners, LLC

  17. #17
    Advanced Tuner CCS86's Avatar
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    Quote Originally Posted by Eric@HPTuners View Post
    This will keep the TB from closing when this limit is hit.


    Thanks Eric, hoping that hits FPDX soon!

  18. #18
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    Quote Originally Posted by Eric@HPTuners View Post
    This will keep the TB from closing when this limit is hit.
    I was hoping this is what that section did, so 0 on off, 1 is on?