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  1. #1

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    Sea-Doo S/C Whats the Maximium Impeller Speed? Lets just spin them faster?

    In every supercharged application Ive ever worked with (all belt driven,, given...) if you want more boost, your put a smaller pulley on the S/C and spin it faster. For instance, on my supercharged Honda, if I want to turn up the boost, I get a smaller pulley which runs the S/C faster which makes more boost, pretty simple right? Well, my vortech unit has a max S/C impeller speed of 55,000 RPM, so I have to be careful how small a pulley I run, so as not to over spin the supercharger. My car red lines at 10k so this is a concern for me, as I cant run smaller than a 4" pulley maing 14psi, or I'll overspin the S/C over the max 55k impeller speed at 10k RPM's. We know all these numbers and figures, for belt sizes vs boost at RPM for our Honda, so its easy to pick the pulley size you need, but Im getting off track. Do we have any kind of info like this on these S/C's if not we need to get it, someone must have it.... It just shocks me that this has not been looked into yet.

    I noticed this RE impeller (Les A-kit) that everyone is talking about that makes 11PSI of boost at 8100, but then what will it make at 8600?? Close to 15psi I would say, no?? Why has no one asked this question yet? I have a hunch, but this brings up a question I have been wanting to ask even more. Does anyone know the maximum rated impeller speed of these S/C's and if so the variances with different impellers??

    There has to be a simple way to just spin these things faster.... The focus has been on impeller efficiency, but how come impeller speed has never been discussed. They make an overdrive double gear flywheel for the GTX model to run the S/C at 215 levels, why not make an overdrive RXP wheel that runs the S/C at its maximum impeller speed, which certainly MUST be increased by these high end super efficient impellers... They may not be as efficient at these higher speeds, but I sure as hell bet every single S/C will make more boost at every RPM.

    Did I just miss 4tec S/C's 101 since I recently joined the forum, or has this REALLY not yet been looked into??? Its a shame if the S/C specs being top secret are what is holding us back. But I'd would dam near GUARANTEE the fellas at the S-Doo plant left a margin of error in that max impeller speed, especially since you guys are running them at 8600 engine RPM with no issues.

    P.S. Does any know what the drive gear ratio is for the S/C on an RXP?? (Engine RPM - to - S/C RPM Ratio?) I'll calculate it from the gear teeth later if no-one knows it.

    Comments? Ideas? Theory's? Answers? Lets discuss overdriving these things!
    Last edited by boostaholic; 01-04-2008 at 04:13 PM.


  2. #2
    Jeepster's Avatar
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    One thing i do know is that (i must redo my maths classes...!!!)
    Last edited by Jeepster; 01-04-2008 at 05:40 PM.

  3. #3
    Site Admin Green Hulk's Avatar
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    Quote Originally Posted by boostaholic View Post
    There has to be a simple way to just spin these things faster....
    There really isn't. It has already been tried with disasterous results.
    To drive the SC faster it would need a smaller gear. The stock RXP/T gear is 16 teeth. To make a 15 tooth gear would make the gear thinner and weaker. It has been tried and the gear fails.

    Supercharger speed is equal to 5.5 times engine RPM

    8100 engine rpm = 44550 rpm on the supercharger
    8500 engine rpm = 46750 rpm on the supercharger
    8800 engine rpm = 48400 rpm on the supercharger

  4. #4
    Hydrotoys's Avatar
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    Once again.... talk to Ted. This is right up his alley. A larger gear on the engine would work as well.

  5. #5
    mxl16's Avatar
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    There's got to be some material that the gear can be made out of to keep a smaller gear from failing.

  6. #6

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    The main thing we need to know is what is the max impeller speed these S/C's are rated for? A stock OEM S/C spec would do, or at least be a start. We could extrapolate from there that a lighter, better balanced impeller would only increase this maximum speed.

  7. #7
    mxl16's Avatar
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    you would need to determine the weak links in the chain, so to speak. Any component on the "rotating assembly" of the sc has to be analyzed to determine its fatigue life/endurance limit. There might be multiple components that will have to redesigned in order to do this safely. bearings obviously would have to be looked at, impeller material (flex)...ect.

  8. #8
    EZ Dock of Long Island Shibby1485's Avatar
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    it's been done and it's been run... and they've moved on to finding different alternatives, if that says enough...

    changing the supercharger gear will also require changing the overdrive gear set on the crank

    for example... the 185 HP supercharged 4-tecs have a 17 tooth gear on the SC and 88 tooth gear on the crank

    215 HP SC 4-tecs have 16 teeth on the SC gear and 87 teeth on the crank ... essentially a 5.4375:1 ratio



    the crank gears are a solid piece with two different sets of teeth cut into it for two things... the starter drives off the inner gear and SC off the outter

  9. #9
    Jeepster's Avatar
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    Greenhulk you are right, i made a mistake in my previous post...i knew the supercharger used to turn around 42-44K SC speed, and i have no freakin' idea (what was i thinking to give the 8 times more)...as 44K divided by 8.1K really makes 5.4...!!!

    Sorry i guess i should relearn my whole maths...!!! Or at least stop drinking...!!!

    I'l edit my post to reflect that, thanks for the clarification from you on that.

    Shibby: Very nice explanation about the ratios...Thumbs up to you too.
    Last edited by Jeepster; 01-04-2008 at 05:44 PM.

  10. #10
    Site Admin Green Hulk's Avatar
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    Malte will have more info on this thread. He is in the know on the over drive gears. I'll shoot him a pm alerting him of this thread.

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