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Thread: Desired Airflow Oddness

  1. #1
    Senior Member
    Join Date
    Oct 2007
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    170

    Default Desired Airflow Oddness

    Ive been trying to get this car to stay running at various points in the temp range. The biggest one that boggles me is full warm temps.

    I can start the car from being off overnight. Start it up, drive. It run at full 180 for good 10-15 min. Says it needs .6lbs more of air.

    But turn the car off, let it sit maybe 5 min. Start it back up and now its saying its subtracting -.98lbs of air.

    WTF? Now if it was smaller incraments, so be it. But that is a hugh difference. How do I tune for something like this?


    Now also, for anyone not familer with my setup. This is on a TPI motor, with a TPI IAC.
    11 Silverado
    08 Sierra
    91 RS with 350 TPI and 411 ECM

  2. #2
    Senior Member
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    Oct 2007
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    Default

    Here is a log file. Please help me figure it out.

    Somewhere around "21:15" is where the car is full warm. I turn it off for a few seconds, then start it back up.
    Attached Files Attached Files
    11 Silverado
    08 Sierra
    91 RS with 350 TPI and 411 ECM

  3. #3
    Lifetime Member hquick's Avatar
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    Jan 2007
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    1,356

    Default

    Without looking at the log....(don't have time right now) I think you'll find the motor keeps getting hotter after it's been sitting for a little bit (no cool air to cool the radiator) and therefor it may have something to do with your ECT VE settings.
    Howard

    YOU ONLY NEED TWO TOOLS IN LIFE - WD-40 AND DUCT TAPE. IF IT DOESN'T
    MOVE AND SHOULD, USE THE WD-40. IF IT SHOULDN'T MOVE AND DOES, USE THE
    DUCT TAPE.
    IF YOU CAN'T FIX IT WITH A HAMMER, YOU'VE GOT AN ELECTRICAL PROBLEM.


    98 K1500 'HOLDEN' Suburban.
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  4. #4
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    Default

    Cant find that chart quick, do you know the number of it off the top of your head?
    11 Silverado
    08 Sierra
    91 RS with 350 TPI and 411 ECM

  5. #5
    Junior Member
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    Dec 2005
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    16

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    "Increased the Startup Friction Airflow Correction table for better starts. Although this doesn't really have to do with idle swing, I thought I'd include it because it seems to be a common problem. I increased this table by 4 grams/second across the board. Now, my warm start issues are gone. It was stumbling right after startup, barely running because there wasn't enough initial airflow. Adding air in here is a good, temporary way to add in the airflow, which will be decayed out after the first 30 seconds or so."

    What about this from the idle tutorial for warm starts?

    edit: just read the first post again....are you having warm start stumbling? or just the incorrect desired air readings?
    ack, yeah, im a rookie

  6. #6
    Senior Member
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    I'm having just incorrect/drastic differences in desired air readings after the motor is warm and restarted.

    Rookie or not, any input is helpful.
    11 Silverado
    08 Sierra
    91 RS with 350 TPI and 411 ECM

  7. #7
    Senior Member
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    Oct 2007
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    170

    Default

    ok. Bringing this back to the top.

    I have loaded an LS1 version of chart B4403. It has helped, but is still off.

    When I bring the car from a cold start, warms up. Its steps move to about 180'ish. turn the car off, start back up, the steps jump to about 110-115. What would cause the steps to change even though the motor temp is the same?
    11 Silverado
    08 Sierra
    91 RS with 350 TPI and 411 ECM

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