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Thread: Quick dual TBI question

  1. #1
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    Quick dual TBI question

    Would it be possible to do a mpfi mod on the 0D minus removing the resistors on the ecm and runn 2 TBI's. Wire both IAC in parrallel and use only 1 tps. Saw a video of a truck that that was done to it but since he didn't have tuning equipment for the ecm he had idle issues.

  2. #2
    Super Moderator Six_Shooter's Avatar
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    There's no MPFI modification needed when using throttle bodies.

    Wire each pair of injectors in series and the each of these pairs to an injector driver circuit,

    Wires the IACs in parallel like you suggest and run a single TPS, then tune.
    The man who says something is impossible, is usually interrupted by the man doing it.

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    Any suggestion on a good inexpensive injector driver circuit.

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    Super Moderator Six_Shooter's Avatar
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    What's wrong with the one in the PCM currently?
    The man who says something is impossible, is usually interrupted by the man doing it.

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    i only ran one iac valve and it does good on its own.

  6. #6
    Super Moderator Six_Shooter's Avatar
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    It depends on the physical layout of the throttle bodies whether one or two would be a better choice.

    If the TBIs are mounted more centrally like a carburetor, like a friend of mine does where he cuts the throttle bodies welds them together and mounts them on conventional carb intakes, then one IAC is usually plenty.

    However, if the throttle bodies are mounted more independently, such as the crossfire intake, then an IAC on each throttle body is a better choice, or needed to ensure that fueling and air delivery to all cylinders is as even as can be. I would use this same idea when using a dual quad intake, or any intake where the throttle plates on each throttle body are separated by more than a couple inches. This includes common plenum intakes. FWIW, the crossfire intake is a common plenum intake, and GM put an IAC on each throttle body.
    The man who says something is impossible, is usually interrupted by the man doing it.

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    isnt it common to run one iac on the crossfire and install a balance tube between the throttle bodies?

  8. #8
    Super Moderator Six_Shooter's Avatar
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    Quote Originally Posted by tayto View Post
    isnt it common to run one iac on the crossfire and install a balance tube between the throttle bodies?
    Nope.

    GM installed two IACs, and that was for idle air distribution reasons.
    The man who says something is impossible, is usually interrupted by the man doing it.

  9. #9
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    Quote Originally Posted by Six_Shooter View Post
    What's wrong with the one in the PCM currently?
    Oh nothing I just assumed for a moment that you meant I would need a separate one to handle the increased current load.

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