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  1. #1
    EZ Dock of Long Island Shibby1485's Avatar
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    Who's the mathematician that can compute a CFM figure for me?

    trying to find out the CFM consumption of the 155 HP 4-tec motor at 7500 rpms

    naturally aspirated motor, same 1500cc motor, rated 155 HP from seadoo... how can i figure out the CFM demand of the motor at approximately 7500 rpms?

    doesn't need to be exact, but semi-close

    Thank youuu

    STEVE


  2. #2
    The ski's have taken a "backseat" to the Corvette DarthAWM's Avatar
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    Quote Originally Posted by Shibby1485 View Post
    trying to find out the CFM consumption of the 155 HP 4-tec motor at 7500 rpms

    naturally aspirated motor, same 1500cc motor, rated 155 HP from seadoo... how can i figure out the CFM demand of the motor at approximately 7500 rpms?

    doesn't need to be exact, but semi-close

    Thank youuu

    STEVE
    You're buying a Demon carb for that ski aren't you?

  3. #3
    EZ Dock of Long Island Shibby1485's Avatar
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    LMAO...

    no no... i haven't totally lost my mind yet, haha

    i think someone once calculated that if u install a bilge blower fan on the RXP air intake that is pressurized the air intake at idle and at something like 3000 or 3500 rpms the supercharger / motor "out sucks" the bilge blower

    so what i'm trying to figure is what about the NA 155 HP ski with no supercharger? for arguments sake if i slapped a 4" attwood bilge blower in the air intake, at what point would the CFM demand of the motor over-take the fan... or maybe it wouldn't with this ski?

  4. #4
    GTXX's Avatar
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    200-203

  5. #5
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    I can tell you just by looking at the conceot that the motor will out pull what the blowr can push VERY EARLY in the RPM range...

  6. #6
    mxl16's Avatar
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    cfm is calculated using (rpm*displacement) / 3456.

    7500*91.5 Cu In /3456 = 198cfm required

    that is theoretical

  7. #7
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    Quote Originally Posted by mxl16 View Post
    cfm is calculated using (rpm*displacement) / 3456.

    7500*91.5 Cu In /3456 = 198cfm required

    that is theoretical


    per cylinder?

  8. #8
    Moderator OsideBill's Avatar
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    Quote Originally Posted by GTXX View Post
    200-203
    Nevermind Danny posted it while I was posting

    Out of curiosity how did you arrive at this number?
    What's the formula used?

  9. #9
    EZ Dock of Long Island Shibby1485's Avatar
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    i came up with like 198 myself... wanted to verify

    is that per cylinder or entire motor?

    i believe a high enough powered large enough fan can out push the motor for a very large part of the rpm band

    obviously not a SC motor tho

    4" detmar is what i'm using

  10. #10
    GTXX's Avatar
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    the one mxl16 used is the simplest. RPM x Displacement/ 3456

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