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Thread: Startup airflow delay

  1. #1

    Startup airflow delay

    So I?m told to add 50-100 cam revolutions to startup airflow delay. The numbers appear to be in seconds. Original table is all zeros. Am I missing something? Thanks
    Last edited by Mood1977; 06-16-2021 at 08:36 PM.

  2. #2
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    What vehicle is it? What are you trying to accomplish?

  3. #3
    Quote Originally Posted by kevin87turbot View Post
    What vehicle is it? What are you trying to accomplish?
    Sorry for the vague post. It?s a p01 pcm. From 2000 5.3. I?m swapping 86 c10 with a 408. Trying to create a tune to crank it. I?m reading to increase base airflow by 2 g/sec, startup airflow initial by 2 g/sec, increase startup airflow delay by 50-100 revolutions to help idle with a 230 @.05 cam.
    Last edited by Mood1977; 06-17-2021 at 05:59 PM.

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    You'll likely be adding A LOT more than just 2 g/sec of base airflow. You'll probably need to add a lot more than just 2 g/sec to the startup airflow as well. The startup airflow delay isn't very critical once you properly setup the base airflow and startup airflow and set your throttle body for proper IAC function.

    However, there are many more important changes that need to take place before you start the engine.

    The important stuff is to have the basic calibration info in the tune.

    Make sure that you have the proper cylinder vol in the engine displacement tab.
    You'll also need all of the injector characterization data in your tune.
    Finally, you can dial in your fuel curves...VE table and/or MAF table and PE settings.
    After all of that, the timing tables can be optimized.

  5. #5
    Thanks for taking the time to give advice. I’m new to this. I did change cylinder volume. I changed injector data. I have it set to fail the maf. So I can tune in speed density. Would you recommend changing the base and startup airflow by a percentage for a starting point? I’ll leave the startup airflow delay alone. Thanks again.

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    Quote Originally Posted by Mood1977 View Post
    Thanks for taking the time to give advice. I’m new to this. I did change cylinder volume. I changed injector data. I have it set to fail the maf. So I can tune in speed density. Would you recommend changing the base and startup airflow by a percentage for a starting point? I’ll leave the startup airflow delay alone. Thanks again.
    Give us the specifics of your build and we'll be glad to recommend the proper changes that need to be made.

  7. #7
    Engine is a 408 with cnc ported TEA 243 heads. 11.0:1. Cam is 227/233. 113 l/s. Holley hi ram. Fic 525cc injector. 213-4222 maf and 213-4681 map. P01 ecm. Just let me know what I forgot. Thank you.

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    I'd typically target 22 degrees timing at peak torque and 24 degrees at peak hp with an application like that.
    Shoot for around 12.7-12.8 AFR at WOT. That'll get you close.

  9. #9
    Thanks, going to try to get it cranked tomorrow.

  10. #10
    So what’s the proper way to set the throttle body butterfly . It’s a Holley with adjustment on tps sensor.

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    Quote Originally Posted by Mood1977 View Post
    So what’s the proper way to set the throttle body butterfly . It’s a Holley with adjustment on tps sensor.
    Once you have it up to operating temp, monitor the IAC position at idle. You'll have to adjust the TB blade to get it in the 40-70 range.

  12. #12
    Quote Originally Posted by kevin87turbot View Post
    Once you have it up to operating temp, monitor the IAC position at idle. You'll have to adjust the TB blade to get it in the 40-70 range.
    Ok. Sounds good. Should the tps read 0 percent while at idle?

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    Quote Originally Posted by Mood1977 View Post
    Ok. Sounds good. Should the tps read 0 percent while at idle?
    Yes it should.

  14. #14
    Quote Originally Posted by kevin87turbot View Post
    Yes it should.
    Thanks again sir.

  15. #15
    Quote Originally Posted by Mood1977 View Post
    Thanks again sir.
    Should this be done before the idle airflow tables have been properly set up?

  16. #16
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    It would be best to get the IAC adjustment close, then you can fine tune the airflow tables.