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  1. #1

    can some one school me on rpm and how they are produced

    ok just want to know how rpms work and how they can be raised and lowered and how to tell if there slipping


  2. #2
    Lbaronio's Avatar
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    The supercharger blows air into the motor (oem X suposed to blow around 10psi) and if the motor its ok, you suposed to have around 8000rpm...
    In case you have a RXP version, it happens the same BUT your charger will blow around 7psi...

    Well, if your charger its slipping, you could reach 7600-7700 or maybe 7400rpm..., this is because its not enough air to reach the RPM desire...
    BUT there are many reasons why this could happen..., not only the Supercharger slipping..., (it could be cavitation, bad propeller, etc,etc)
    If youre thinking you have a problem with the Supercharger, just need to take it out and make a simple slipping test...
    You would need a torque wrench...

  3. #3
    well thanks that was very knowledgeable not sure if it is going to be the supercharger or the prop. it will only turn about 7500 rpm on a wot run but from a stand still it will turn about 8300 then come down slowly i need to check the propeller the ski only has 22 hrs on it so im not leaning to the prop i think it is still stock is the torque setting in the book or something you just learn with time ?

  4. #4
    wotxxxsd's Avatar
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    I've seen a loss of high rpms when a ski is over full on oil.
    Check your oil when hot. After 15 min ride and make sure u idle for 30 seconds before shutting it off.
    It should b half way between the 2 marks on the stick.
    Also put some fuel treatment in.
    Could be a fuel Injector getting some trash in it.....

  5. #5
    dnielsen's Avatar
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    RPMs are in direct relation to the load of the engine and horsepower generated and limited by the ECU. Add more horsepower by increasing the boost from the supercharger in conjunction with the appropriate fueling and your RPMs will increase (as long as your not reaching the rev limiter of the ECU). You can then add pitch to the impeller to reduce the RPMs to match your ECUs maximum RPM range. Why do you want to reduce the RPMs at this point? Well, you have now added power so you need to convert the power to thrust from the pump to gain more speed without hitting the rev limiter (loading the engine by tweaking the prop).

    All this is true if the craft is in good working condition, a poor or slipping supercharger, a bad or bent impeller, a worn wear ring in the pump, poor fuel, poor AFRs, bad plugs, hot weather (affects the effeciency of the IC) to name only a few things that could poorly affect performance.

    You ever wonder why some guys can put up speed numbers with a stock ECU that rival those with the higher rpm aftermarket ones or a higher RPM reflash. Simple, they make more power with higher boost superchargers then convert the power to thrust by raising the pitch on the impeller. It's all a power to thrust game (along with a good machine setup).

    If your RPMs a dropping check the slip of the supercharger, your plugs, make sure your running fresh fuel, etc. etc. and be sure that the loss of RPM is not due to hotter weather.

  6. #6
    Well the plugs are new the fuel is fresh as for the impeller and wear ring the ski only has 20 hrs on it i did take it off and check just to be sure everything looked good. what is the best way to check the sc with a torque wrench and when should it slip. ps great post very good info

  7. #7
    If i knew,...I wouldn't ask sea-one's Avatar
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    RPM's!!!!! W F O yea!

    ....thats how i get mine

  8. #8
    dnielsen's Avatar
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    Quote Originally Posted by 4pinwink View Post
    Well the plugs are new the fuel is fresh as for the impeller and wear ring the ski only has 20 hrs on it i did take it off and check just to be sure everything looked good. what is the best way to check the sc with a torque wrench and when should it slip. ps great post very good info

    Here is some good info on how to check the slip http://www.greenhulk.net/forums/show...ercharger-Slip

    Here is some more info on the superchargers, old thread but good information http://www.greenhulk.net/forums/showthread.php?t=19887

    Here is information on how to remove the supercharger if you want to check slip out of the ski http://www.greenhulk.net/forums/showthread.php?t=13403

    And also information for the techy guys that want to check the condition of all the internals of the charger, great write up and good information http://www.greenhulk.net/forums/showthread.php?t=71442

    And finally information on how to shim the chargers to increase the slip moments if found to be low http://www.greenhulk.net/forums/showthread.php?t=78668

    Hopefully this will help you diagnose your problem or atleast rule out the charger if it test good.

  9. #9
    i ran across this and was thinking that when i bought the ski it only had 19 hrs on it and when i took it in to my mechanic and he put it on the buds system that maybe this has happen to me is it possible it is a 2005 rxt sc ic and thats about where my rpms are 7500 high heat and rough water.


    If your RPM are locked down at 7600-7700 RPM you need to install the knock sensor piggy back adapter part number 278002050

    The reason i bring this up is I've talked to 3 people already this week that have this issue so hopefully this info can help someone else.

    What happens is any time the ECU is hooked up to BUDS a knock sensor update is loaded to the ECU (this ONLY pertains to 04 RXP ECU's)

    In addition to flashing this update to the ECU the dealer is supposed to install a pig tail harness between your stock wire harness and knock sensor connector. If this is not done your RPM's will be locked down to 7600-7700 RPM's

    Hope this helps
    http://www.greenhulk.net/forums/showthread.php?t=105724

  10. #10
    so i guess my next question is do i need one of these if i dont have one Attachment 276292

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