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Thread: Let's talk "Airflow Final Minimum"....

  1. #1

    Let's talk "Airflow Final Minimum"....

    I'm just looking for some answers as to what rows in the idle airflow "Airflow Final Minimum" pertain to a manual transmission car, and if so, when they are used. The Y-axis of the table has transmission gears (1-6), Neutral, Reverse, and Park. This is on a 2013 LS3 Corvette.

    I'm trying to resolve a minor issue where I sometimes get an RPM spike or surging when coasting to a stop with the transmission in neutral. I've made some global adjustments to the minimum airflow table I mentioned, and at this point the surge is only an issue when I release the clutch in neutral. If I keep the clutch pressed in, it's always fine. This is on a C6, so when the clutch is released, there is quite a bit of drivetrain load from the torque tube parts, etc.

    So I'm hoping someone can give me a solid answer. What section of the table is the ECM using when the clutch is let out in neutral while coasting? I wouldn't think the "1st Gear", "2nd Gear", etc. rows would do anything on a manual car, or would the ECM have any clue what gear you were in if the clutch was in. I'm assuming it's using the "Neutral" portion of the table when the clutch is on the floor -- but I don't have a clue with the situation where I'm having my issue.

    I know I can just keep messing with it until it goes away, but I'm hoping to actually learn how the table is used so I can adjust exactly what is needed vs. just blindly adding airflow to all cells.

  2. #2
    All I know is that I had the same issue with my new injectors. I just removed about 20% from the whole table. Like you, I didn't fully understand which section of the table did what, that's why I removed 20% from the whole table. It works however. Adding airflow to the table it would make your problem worse, if it's anything like mine.
    2012 Camaro SS/RS M6. TVS2300 w/rear OD cog drive and ported lower manifold, On top of a forged 416.
    1999 GMC Sierra 2500. Stock 6.0L, LT headers, cat delete, and Airaid intake.
    1965 Oldmobile Cutlass. 5.7L LS1/4L60E transplant in progress from 98 TransAm donor car.

  3. #3
    Originally, mine would drop down below regular idle speed, then it would spike up. Sometimes doing this over and over again until I intervened. I added air to the table and that has been mostly corrected.

    Right now, I might have too much air in a certain area of the table. Sometimes I've noticed that if I : put the clutch in, slow to a stop, then right as I come to a complete stop release the clutch in neutral -- the rpms will flare up to 1000-1200 or so before going back to normal. I'll have to pay more attention to it, because I don't think it's dropping down below regular speeds when it does this.

    I'm going to try and log transmission gear to see if I can tell what section of the table it might use when I let the clutch out at idle or coast like that.

  4. #4
    Mine did the same. When at a complete stop it didn't care if the clutch was in or not. If I was moving at all and I let the clutch out in neutral, it would shoot up in RPMs until I came to a stop.
    2012 Camaro SS/RS M6. TVS2300 w/rear OD cog drive and ported lower manifold, On top of a forged 416.
    1999 GMC Sierra 2500. Stock 6.0L, LT headers, cat delete, and Airaid intake.
    1965 Oldmobile Cutlass. 5.7L LS1/4L60E transplant in progress from 98 TransAm donor car.

  5. #5
    Advanced Tuner
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    When arguing with an idiot, make sure he isn't doing the same thing....

  6. #6
    Senior Tuner
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    Leave the idle air table alone if it idles well and returns to idle well after say a high rpm rev, AND doesn't feel like it's got cruise control all the time.

    Just copy your idle spark over/under tables from the P/N correction into the in gear and coast (neutral and drive) columns. Problem solved.
    2010 Camaro SS M6. Stock Bottom End, Heads/Cam/Intake/Headers/Exhaust.
    2005 Silverado RCSB. Forged 370 LQ9/Borg-Forced Inductions T6 S484/Jake's Stage 4 4L80E with D3 Brake/4WD.
    2023 Durango Hellcat

  7. #7
    Quote Originally Posted by MikeOD View Post
    Leave the idle air table alone if it idles well and returns to idle well after say a high rpm rev, AND doesn't feel like it's got cruise control all the time.

    Just copy your idle spark over/under tables from the P/N correction into the in gear and coast (neutral and drive) columns. Problem solved.
    Might have to give that a try. Overall, it has very good behavior. The only thing I have to complain about is that idle spike that happens with the clutch out in neutral. The revs don't seem to hang (cruise control feel) and in any other situation, it returns to idle very well.

  8. #8
    Senior Tuner
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    Quote Originally Posted by BMWMD82 View Post
    Might have to give that a try. Overall, it has very good behavior. The only thing I have to complain about is that idle spike that happens with the clutch out in neutral. The revs don't seem to hang (cruise control feel) and in any other situation, it returns to idle very well.
    Yeah, then what you're describing screams to me that you need to correct those spark correction tables I mentioned before.
    2010 Camaro SS M6. Stock Bottom End, Heads/Cam/Intake/Headers/Exhaust.
    2005 Silverado RCSB. Forged 370 LQ9/Borg-Forced Inductions T6 S484/Jake's Stage 4 4L80E with D3 Brake/4WD.
    2023 Durango Hellcat