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Thread: Anybody ever try tuning the transient airmass stuff?

  1. #1
    Tuner in Training
    Join Date
    Nov 2006
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    Out of my mind, be back in five minutes...
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    48

    Anybody ever try tuning the transient airmass stuff?

    Im using a vortec blackbox PCM on my setup. Its similar to the early LS1 PCMs in that it uses the transient air calculations along with the MAF/SD logic for deriving the cylinder airmass. I disabled the SD for the most part and just run MAF and open loop. I also disabled most of the transient airmass multipliers except for the TPS and delayed TPS for throttle opening. I also disabled all the filtering on the cylinder air masses due to the engine wanting to stall on tip in. The car is very drivable and it revs well, but I have a large 4 bbl throttle body, and when I quickly open all 4 barrels, the engine snaps out the intake due to the lean spike. Ideally, Id like to try to use the other terms as well for the transient airmass calcs to see if I can reduce the lean spike during a WOT stomp. Anybody mess with these yet? Looking for some tips on what works.
    Old rusty 88 Camaro
    350 w/ Edelbrock victor EFI intake + 1000 CFM TB
    '279 PCM with a custom tune and code patches by me
    TKO 500, 1LE performance package, etc...

  2. #2
    Tuner in Training
    Join Date
    Nov 2006
    Location
    Out of my mind, be back in five minutes...
    Posts
    48
    Found out what it was that was causing all the backfires. It was how the injector driver sampling was set up. GM only allowed certain other drivers to sample the pulsewidth under transient conditions (presumably to dampen the response) when each driver came up in the firing order. It was causing the engine to go lean for a few injector firings. I set each table up to allow all drivers to sample the pulsewidth so none would fall behind during transients, and very little extra airmass is needed. I can snap all 4 barrels open w/o issue now.

    Dont know if you guys have access to these tables in HP Tuners, but they really speed up the response when all injectors are allowed to sample.
    Old rusty 88 Camaro
    350 w/ Edelbrock victor EFI intake + 1000 CFM TB
    '279 PCM with a custom tune and code patches by me
    TKO 500, 1LE performance package, etc...