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  1. #1

    pump tunnel pop off valve

    Just a thought. Knowing the pump tunnel pressure at hi speed is enough to crack the gp hull and cause hi speed bucking, this has to be far more water pressure than the pump requires to feed it at speed.
    Engineer a way to measure pump tunnel pressure then controlling that pressure as it increases with speed with a (pump tunnel pop off valve) similar to the way a turbo or supercharger is controlled.
    Reducing the excess intake water pressure should reduce a huge portion of unecessary drag from the ski..
    I would try it but for some reason im afraid to drill holes in my hull at the pump tunnel to create the pressure bleed system...
    Any ideas on this?


  2. #2
    Happily Self-Employed WFO's Avatar
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    Lightbulb

    whoa...great idea

  3. #3
    cheatin' piston popper addicted's Avatar
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    I don't even have a GPR, but after reading alot about this problem, I started envisioning a shifting intake grate, that works like the AAT. Wide open for holeshot, and closes when more pressure is applied. . .

  4. #4
    r33pwrd's Avatar
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    only problem with that is making a grate that would not fatigue! I could make one out of nitinol, It would only be around 5K bucks a piece I make at work is .0165" dia and deflects almost 1/4 inch and has gotten to 400million cycles without breaking yet!!

  5. #5
    WATER WOODY's Avatar
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    Sounds good but as soon as you take pressure out of the pump area,say bye to your top end.Example: if your bolts on your strainer come loose and you lose your seal,it could cost you 1/2 to 1 mph because of pressure loss.How do i know this? I very respectable source shared the story with me.

  6. #6

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    I do not think that it is a question of pressure, but a question of volume. Seems to me that the higher the intake pressure/velocity (pressure of movement), the higher the exit pressure/velocity. That is to say the greater the speed. Would we not want a perpetual vacume in the intake to pull water into the intake so that it can be accellerated out of the back.....even at high speeds?

    It seems to me that a fixed sized pump can only process so much volume, and a fixed volume pump matched with the proper sized impeller and engine can be very efficient. This volume that our intakes are capable of seems to be considerably more than most of our engines can handle. With a fixed sized intake, the faster you go the greater the volume there is available to processs due to dynamic pressure of movement. There always seems to be to much volume to handle. This to my thinking is why we need a bigger and bigger engine, and a bigger and bigger impeller to process the greater amount of water. We would be getting more and more efficient until we reach pump capacity.

    We are talking direct drive here.

    The alternative would be to have a "transmission", something to reduce the amount of volume on the intake without reducing the pressure or velocity on the water at the intake.... give the pump just what it needs at any particular speed. The excess water volume no longer slows the boat down so the engine can use the extra power to accellerate water through the pump tunnel with greater velocity. As we go faster we would reduce the intake size. It is not just a matter of reducing the intake size though, it is also seems to be a matter of changeing the intake shape as well.

    Heck, if reducing the size were the case, we all would have recessed our shoes to the max and be done with it.

    Does this make any sense?
    Last edited by salty; 09-29-2006 at 08:38 PM.

  7. #7
    ....back from the dead.... J-ME's Avatar
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    Quote Originally Posted by addicted
    I don't even have a GPR, but after reading alot about this problem, I started envisioning a shifting intake grate, that works like the AAT. Wide open for holeshot, and closes when more pressure is applied. . .
    Hmm..sounds like the spike at the inlet of the J-58 engine of the SR-71.

    I never thought it was a good idea of the Yami engineers to make the hull a part of the intake "duct", but it was necessary to bury the pump that far up in the hull.

  8. #8

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    Cool

    Safety relief sounds good -now what do you set it at (this means you‘ll have to go out and bust your ass one time to see max pressure!

    later cd

  9. #9
    ....back from the dead.... J-ME's Avatar
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  10. #10
    I'm not an engineer but I do have some experience in busting my ass. This sounds like you folks are on to something there.


    (We crash test dummies just sit and await your call.)

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