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  1. #1
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    SHO math - air flow

    This could be completely crazy, but here it goes...

    On the SHO, the intake is about 4 inches diameter, on the intake is a screen that has little 1/4 inch or so square openings. I wonder what the area of the total opening is, and what the theoretical air flow is through the openings?

    I found a couple calculators on line and estimated the size of the ~4 inch opening, and what a 4.2 liter engine needs at 6000 RPM. It seems like it would flow about 50-100cfm more than the engine needs, but that's not figuring in the restriction of the screen ribs.

    I don't have my boat right now (traded in), so I can't measure the size of the ribs between square openings in that screen to know how much surface opening there is there.

    My theory is, at high RPM that screen could restrict the flow enough to possibly impact performance.

    If this does have any impact, i would assume it would only be up around peak RPM.

    Ive been thinking about it a while, and would like to hear opinions. If I had my boat still, I'd run it with and without the screen to see if there is any change. Even if it let the motor spin an extra 100-200 RPM that might help at the top end.

    Probably not an issue as I've heard of guys spinning the SHO around 6100 RPM. My boat would top out around 5800, so it made me think...

    Just a theory, lots of variables I'm sure, just wondering if a little more top end could be squeezed out of it if it could breathe better.


    Mike

  2. Banned
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    #2
    Maybe but the throttle is controlled by the ecu depending on a mapping for horsepower power rating. A 200 sho throttle may only open up to 75% and a 300hp to 100%. I think that screen is only there to protect the motor from ingesting larger debries. It may help a little if removed as you suggested to increase rpm.

  3. Member
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    #3
    The design of the screen could also induce a vortex. Which in a thermodynamic theory would be helpful.

  4. Banned
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    #4
    Anything that promotes greater airflow into the intake manifold should result in the creation of more HP. The manifold pressure should be higher without the screen installed. The MAP sensor should sense the higher manifold pressure and add more fuel. More air, more fuel, more power.

    Now will it be measurable? Where are out test pilots to prove or disprove this hypothesis?

  5. Banned
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    #5
    I think the plastic shroud covering up the air to throttle body and the screen if removed may produce measurable results. I will make this test just to see if there is anything worthwhile.

  6. Member
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    #6
    The wire on top of the throttle body is dome shaped so it has more air flow than if it was flat. Also if the body is 52 mm it doesn't flow with the full 53 because the throttle plate and shaft take up a fair amount of space in it.
    Last edited by Brianmoore25; 03-22-2017 at 11:25 AM.

  7. Member
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    #7
    52 mm sounds pretty small, are you sure about that number?

    Maybe someone will find the screen is not ideal for flowing ~400 cfm, and can make a new option in the aftermarket.

  8. Member
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    #8
    52mm I think. Also like rich said it only opens fully on a 300 hp.