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Thread: How much the A/F should be when releasing throttle after hard acceleration?

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    Lifetime Member wesam's Avatar
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    Default How much the A/F should be when releasing throttle after hard acceleration?

    How much the A/F should be when releasing throttle after hard acceleration?
    I mean in Manual transmission cars between shifts the MAP goes to 15-25 kpa
    so in this area how much the A/F ratio should be ?

  2. #2
    R.I.P Shawn, 1956-2011 WeathermanShawn's Avatar
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    Mine spikes to 20.0 AFR..DFCO....http://forum.efilive.com/search.php?searchid=941785
    2002 Black Camaro Z-28 M6 Hardtop 11.0:1CR 425HP/410TQ SAE (400TQ@3500RPM)
    200cc Heads, 228/232 110+2 Cam, 1 3/4" LT's w/catts, GMMG, Koni Shocks, Hotchkis Springs, 35/21 Sways, 17" ZR1's, 3.90 Gears Roadrunner PCM LM-2 Serial Wideband
    EFILive Closed-Loop MAF/SD Hybrid Tune..


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    Lifetime Member wesam's Avatar
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    so my car should be recalibrate because I'm seeing 12
    but i want to know what is the ideal A/F for this area

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    R.I.P Shawn, 1956-2011 WeathermanShawn's Avatar
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    Are you saying during shift (clutch-depressed) or after clutch released, but no throttle.

    Neither needs to be tuned. DFCO turns off injectors on M6 during shift..http://forum.efilive.com/search.php?searchid=941790.

    If you get a richer AFR after shift, but foot off throttle..thats momentary. Called rich decel..http://forum.efilive.com/search.php?searchid=941792..

    DFCO you can turn on and off (see links). The other would have to be tuned via transient parameters. (see links)..

    EDIT: Stoich would be ideal..but there is so little cylinder air, it is virtually impossible to decrease the injector pulse width below its minimum. Thats why most tuners don't chase it. But, if you are really curious 5.7ute has novel ways of tuning that area.
    Last edited by WeathermanShawn; May 20th, 2010 at 11:56 PM. Reason: Clarification..
    2002 Black Camaro Z-28 M6 Hardtop 11.0:1CR 425HP/410TQ SAE (400TQ@3500RPM)
    200cc Heads, 228/232 110+2 Cam, 1 3/4" LT's w/catts, GMMG, Koni Shocks, Hotchkis Springs, 35/21 Sways, 17" ZR1's, 3.90 Gears Roadrunner PCM LM-2 Serial Wideband
    EFILive Closed-Loop MAF/SD Hybrid Tune..


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    Lifetime Member wesam's Avatar
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    I meant when clutch-depressed and no throttle what is the ideal A/F ?

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    R.I.P Shawn, 1956-2011 WeathermanShawn's Avatar
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    While technically 'stoich' is ideal..since there is no load on the engine, and very little cylinder air..no fuel is required.

    I say on a M6 enable DFCO B3308. It momentarily cuts off the injectors..

    I do not believe there is any other way to manipulate fueling during a M6 shift other than B3308..
    2002 Black Camaro Z-28 M6 Hardtop 11.0:1CR 425HP/410TQ SAE (400TQ@3500RPM)
    200cc Heads, 228/232 110+2 Cam, 1 3/4" LT's w/catts, GMMG, Koni Shocks, Hotchkis Springs, 35/21 Sways, 17" ZR1's, 3.90 Gears Roadrunner PCM LM-2 Serial Wideband
    EFILive Closed-Loop MAF/SD Hybrid Tune..


  7. #7
    Lifetime Member wesam's Avatar
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    i look in my tune it seems that the DFCO is not active since the B3308 DFCO enable temperature is 140C
    i will try to enable it will i need to tune any thing else after decreasing the temperature ?
    will the car go very lean ? its running in open loop sd

  8. #8
    R.I.P Shawn, 1956-2011 WeathermanShawn's Avatar
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    Its totally known as 'tuners option'. A lot of tuners when utilizing AUTOVE for SD Tuning, disable DFCO. That is to not have the brief interruption of the fuel injectors effect the RPM/MAP wideband readings while tuning AFR.

    A number of tuners after completing AUTOVE leave DFCO disabled. Probably an equal number of tuners re-enable DFCO. Its true you go 'lean' for a moment. Its also considered no-load on the engine..a total waste of fuel to spray 1/2 second of fuel while shifting..and the engine does not need it.

    The bottom line is its your option. Personally on my application, I leave DFCO enabled, including during shifts (M6 DFCO Temp: 50C). As soon as you hit the throttle Commanded AFR only takes 1/16 of a second to re-engage. If you stay rich during throttle shift, most likely you hear a quick 'pop' as any unburnt fuel during shift blows out the exhaust pipe.

    The bottom line is that I have not heard of anyone who can alter the AFR during a M6 shift via any tuning method other than DFCO. I would just do a search on it and make up your own mind. If you are in the active process of AUTOVE..leave it disabled..

    Good luck with your search..
    2002 Black Camaro Z-28 M6 Hardtop 11.0:1CR 425HP/410TQ SAE (400TQ@3500RPM)
    200cc Heads, 228/232 110+2 Cam, 1 3/4" LT's w/catts, GMMG, Koni Shocks, Hotchkis Springs, 35/21 Sways, 17" ZR1's, 3.90 Gears Roadrunner PCM LM-2 Serial Wideband
    EFILive Closed-Loop MAF/SD Hybrid Tune..


  9. #9
    Lifetime Member wesam's Avatar
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    Shawn i'm glad for you for that explanation
    and thanks a lot for told me to leave it deactivated while i'm in the AutoVe tuning

  10. #10
    Lifetime Member wesam's Avatar
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    so is it useful to try to lean those spots after making a log for the car ?

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