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  1. #1

    Displacement versus RPM

    I'm new to PWC's, so please help me understand... I keep reading on this and other PWC forums that "There's no replacement for displacement." But let's pretend we have two engines..

    Engine "A" has a displacement of 1100cc and gets 180 hp at 11000 RPM
    Engine "B" has a displacement of 1800cc and gets 180 hp at 7000

    Ignoring and difference in weight, would one feel any different than the other? Is there something I'm missing?


  2. #2
    Having Fun jp1300r's Avatar
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    Yes there is a difference. Its call "Torque".

  3. #3
    VinceC's Avatar
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    jp is dead right. torque can turn a higher pitch prop and move you further through the water with every revolution. also don't think that the 1800cc engine is all that much heavier. as a example the yamaha is as light or lighter as a ski than most competitors with smaller engines. also that displacement is terribly underutilized. potential for greater speed and still maintain reliability is huge.

  4. #4
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    180 hp is 180 hp it will make the same rpm,,,, now the real difference is in abilty. build both motors and of course the big motor will make more power.
    http://www.mk5cortinaestate.co.uk/calculator3.php to see the difference.

  5. #5
    Having Fun jp1300r's Avatar
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    Here is a question. Take a 2.0L N/A motor that turns 9K and make 240HP and 170Ft,lbs, than take say a N/A Chevy 350 that turns 5.5K and makes 240HP and 300+Ft.lbs. Which has more power?

  6. #6
    305coco's Avatar
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    Quote Originally Posted by jp1300r View Post
    Yes there is a difference. Its call "Torque".

    +1

    horsepower sells parts Torque wins races.

  7. #7
    jetpilot785's Avatar
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    There is another saying as well "It's not always the size but the ingrediants".

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    Cubes always win hands down

  9. #9
    RichieFZR's Avatar
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    Quote Originally Posted by no_more_rice View Post
    Raw horsepower (kW) is what produces speed, if that's what the OP is driving at; a displacement disadvantage can be overcome by boost and sound engineering. I routinely stomp LSx F body 5.7 Ls with a "puny" 1.3 L rotary turbo (drag race, top speed, whatever) and it really pisses them off - boost wins. I just had an M3 driver (these guys are peerless in their arrogance) spin out (i.e. complete 360) tonight trying to get me from a dig, truly hilarious in my rear view, his "awesome torque" cost him traction and he not only lost the race, he lost his pride and just about smashed his car into an embankment. This is why I will always drive an FD RX-7: the endless entertainment factor.
    Boosted LSx always wins hands down. LOL Cubes + Boost = YUM.

  10. #10
    Boilerman Bill BPnta's Avatar
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    Quote Originally Posted by RonS View Post
    I'm new to PWC's, so please help me understand... I keep reading on this and other PWC forums that "There's no replacement for displacement." But let's pretend we have two engines..

    Engine "A" has a displacement of 1100cc and gets 180 hp at 11000 RPM
    Engine "B" has a displacement of 1800cc and gets 180 hp at 7000

    Ignoring and difference in weight, would one feel any different than the other? Is there something I'm missing?
    The skis that turn 10000+ RPM have a reduction gear between the motor and pump, therefore multiplying the torque. It would be the same.

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