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  1. #1
    mongo's Avatar
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    Why no boost unless under load??

    I was wondering if someone could explain why the boost guage doesn't show boost when the ski is reved up on the trailer.

    Thanks Mongo


  2. #2
    Moderator Snoman's Avatar
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    What kind of gauge are you running??Mechanical or electric???Does it show boost when riding??Your motor doesnt produce boost until around 6000 RPM..Until then your motor is under vacumn..

  3. #3
    home of the dislexic fingers breon's Avatar
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    if you watch the manifold when you rev it ...you can see it expand and contract ...your guage just may not read that fast...it amazes me they dont pop ...well more often ...they do at like 18 20 psi

  4. #4
    The gage may be damped so it doesn't bounce and/or it may read after the butterfy valve in the throttle body-inlet chamber just before the valves. Those are the only reasons I can see if I were a guessing man.

  5. #5
    Dave Sharp dav_dman's Avatar
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    you only have to crack the throttle body for the engine to reach high rev's while out of the water in no load.

    Load on the engine would require more air and fuel to get the engine to the same point in the rpm range. The engine is having to do more work to get to the same point due to the load. The more work requires more air and fuel, timing, and more throttle position and more boost.

  6. #6

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    dav has got it.

    "Load", "throttle angle", and "manifold pressure" are almost interchangeable words with NA and supercharged engines. If you're not holding the throttle close to the grip, it's not going to make boost in the plenum. Turbo is a different story...

  7. #7
    mongo's Avatar
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    Got it guys that makes sence.

    Thanks Mongo

  8. #8
    jpeconsult's Avatar
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    Quote Originally Posted by engineermike View Post
    dav has got it.

    "Load", "throttle angle", and "manifold pressure" are almost interchangeable words with NA and supercharged engines. If you're not holding the throttle close to the grip, it's not going to make boost in the plenum. Turbo is a different story...
    There you are!

  9. #9

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    I've got a picture in my mind of a ski on the trailer being rev'ed to the moon.................... with no booost as it goes CLANK......clatter, clatter and goes dead.

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