Draw thru/blow thru ?
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Draw thru/blow thru ?

  1. #1
    Maw
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    Default Draw thru/blow thru ?

    We're planning on converting our PFM twin turbo BBC over to EFI before summer gets here. Plan is to use a Victor Jr EFI manifold and keep the standard large PFM intercooler bolted to it.

    The question is -- do I use a standard throttle body where the carb currently sits (between the turbo's) or add two smaller throttle bodies to the intercooler inlets? A third option could be to add a short four barrel thottle plate between the intercooler and the manifold.

    Any clear cut advantages one way or the other.

    Thanks, Mark

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    mo balls than $cents$ IMPATIENT 1's Avatar
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    most twins i've seen run 2 tb's before the cooler. get with unchained, he's yo man to talk to on this already is runnin the set-up you're wanting.

    Dare to be different, if it turns out great you can claim you planned it that way.

    Jetboatperformance.com

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    Highaboosta Unchained's Avatar
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    You definitely want to blow through the throttle body.
    A pair of them between the compressor and the intercooler or one under the intercooler would work fine. A blow off valve will be required if you like to slam the throttle shut at high boost levels.

    Here's a pic of a Brummett setup with the throttle body under the intercooler,


    A throttle body source,
    http://www.accufabracing.com/

    I have a Victor manifold with EFI bungs I'll sell for $ 125.00
    It has a Dom bolt pattern and is for a tall deck.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Twin Turbo 1800 HP V-Drive lake boat

    http://s621.photobucket.com/albums/t...t=MAH05771.mp4

    Quote Originally Posted by Trigger View Post
    No one cares about your buddies old antiquated garden hose technology.
    Quote Originally Posted by MAXIMUS View Post
    I think I could run more boost but it's a real hand full right now

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  6. #4
    Maw
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    Thank you for the responses.

    As a general rule is there any perfomance difference between the blow through and draw thru systems?

    I see 2000 hp systems with turbos blowing through a single 850 Holley DP, then look at the early Banks and PFMs drawing through a pair of the same carburetors, while rated for "only" 850 hp. I don't understand the relationship between the throttle area, blow/draw thru, and horsepower (assuming there is an easilyunderstandable one).

    Thanks for the offer on the manifold but this is a standard deck motor.

    Cheers, Mark

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    mo balls than $cents$ IMPATIENT 1's Avatar
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    blow thru is gonna make more hp we're building a 496 and hope'n for 1500hp+ on pump gas alone, low boost levels.

    Dare to be different, if it turns out great you can claim you planned it that way.

    Jetboatperformance.com

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    Default Blow Thru Vs. Draw Thru

    I have built 4 turbo engines, from carbs to mech. fuel inj. They have all been blow thru. They always performed better than the draw thru systems. ONE VERY BASIC FACT: TURBOS ARE DESIGNED TO MOVE AIR, NOT LIQUID. The compressor impeller does not like the extra burden of moving fuel laden air.

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    Highaboosta Unchained's Avatar
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    Quote Originally Posted by J. Shelfo Sr. View Post
    I have built 4 turbo engines, from carbs to mech. fuel inj. .
    What'sa matter, you don't like them lectronics ?

    Twin Turbo 1800 HP V-Drive lake boat

    http://s621.photobucket.com/albums/t...t=MAH05771.mp4

    Quote Originally Posted by Trigger View Post
    No one cares about your buddies old antiquated garden hose technology.
    Quote Originally Posted by MAXIMUS View Post
    I think I could run more boost but it's a real hand full right now

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    Quote Originally Posted by Unchained View Post
    What'sa matter, you don't like them lectronics ?
    Electronics were just breaking out when I did these engines, Anyway the dragboat associations did not allow electronic fuel injection!

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