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Boosting the 3900VVT and MAP question

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  • Boosting the 3900VVT and MAP question

    Hi guys, I'm new to GM engine management (and everything else) coming from mostly Nissans and am considering a jump to forced induction later this year.
    However I have to learn about the whole MAP sensor setup in conjunction with the MAF on my 2008 Uplander Cargo. My target is around 4-5psi to gain about 40-60 crank hp, anything more I think could be potentially deadly in a minivan lol.

    Anyway, do you guys know if a 2 bar MAP sensor can be used in place of an NA 1 bar sensor with the appropriate PCM tuning?

    I want to keep things as simple and OEM as possible but have heard that if the 2 bar isn't offered on a given platform to begin with, it may not be possible (or easy).

    With my Nissan I was able to upgrade injectors, fuel pressure regulator and computer tune for an initial and reliable turbo setup but things seem to be different on the GM.

    I'll be doing my research but wanted to touch base with you experienced turbo guys, especially w/the 3900 and 3500 V6.



  • #2
    If I'm not mistaken in those PCMs, the MAP is used primarily for spark timing and the MAF is used primarily for fueling with ability to use either as a backup in case one or the other fails.

    It seems that many people get away with upsizing the MAF sensor appropriately so that it doesn't get maxed out in air flow, and then tune. For spark you'd basically tune the upper kpa cells for the lowest timing needed and the PCM will just use those cells for the timing control.

    Check out some forums for later model W and N bodies where people have added forced induction and see exactly how they went about it.


    • #3
      Apologies for the delayed response but thanks for the input Raven...Just too many irons in the fire at this time but I'll be doing my research on a low boost setup for next year. The 4spd auto gearing is a little tall in some situations and I'd really like another 30-40hp at least to work with.


      • #4
        what we do when we apply boost to late model gm vehicles is we get a map sensor for a chevy cobalt ss or a c6 zr1 corvette and we use hptuners to convert the ecu to a 2 or 3 bar os. and now the ecu can see when the intake manifold is under boost. and there are extra breakpoints added for those higher kpa levels. then we tune the ve tables in the newly added reigons and then we tune the maf. and the ecu works the same way it did from the factory, just now it uses boost. the right way. the other way is the canned tune way. it forces all fueling off of the maf. while a lot will argue this method works, I would like to point out that to date not 1 car has left a manufacturing plant tuned like that. every boosted oem application the ecu sees boost. tuning shouldn't be about what you can get away with, but how good you can get it.