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  1. #1
    Vern's Avatar
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    Boost leak? Input?

    I had 25 hours on my metal washers, stock supercharger, which always ran 7 lbs of boost. Boost was starting to drop a bit, to 5 & 6 lbs sometimes and rpms would drop to 7700 range, but bounce up sometimes. I pulled that supercharger and installed my brand new Les Cooke A kit SC which is supposed to push around 10 lbs of boost. I think this is very similar to the RR SC impeller, so I was expecting to see at least 9 lbs of boost. I also added 42lb injectors. Strange ... I saw no additional boost and am still getting some boost and rpm variance. I sprayed soapy water on all the connectors and blockoff, saw a few bubbles on one, tightened it up, but still only 7 lbs of boost and sometimes the rpms and boost drop, then sometimes come back up.

    I am puzzled ... this must be a boost leak since it behaves about the same with either supercharger and I should see more boost with the new SC. Just not sure what else to try? Ideas?


  2. #2
    mxl16's Avatar
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    what did the clutch slip at?

  3. #3
    Vern's Avatar
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    My torque wrench does not actually go low enough for me to trust its accuracy, but the SC I pulled off appeared to slip around 10 NM and the one going in slipped closer to 15+ NM. But this is very unscientific, I need to get a better (low torque range) wrench to really know. So I don't really think the either SC is actually slipping ... I think instead I have a small boost leak that is limiting me to 5.5 - 7 lbs of boost. Seems like the higher the boost goes, the more it bleeds off, so that boost varies. Sometimes it hold 7 lbs at WOT, then it drops off to 5.5 or 6 lbs, then it sometimes goes back up, then drops again. I am running XPS oil, stock ECU rpms vary from 8100 to 7700 dependent on boost. Puzzled ...

  4. #4
    Site Admin Green Hulk's Avatar
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    Quote Originally Posted by Vern
    sometimes the rpms and boost drop, then sometimes come back up.
    Dead give away to a boost leak Vern.

    Refresh my memory. Riva IC? U running a BOV?

  5. #5

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    Make a hose connector to connect to the hose off the SC and a valve stem and pump it up... I had a 8 lb leak and a 10lb leak... It will be REAL obvious where the leak is. 2.5 in pipe with one end blocked off and sealed with a valve stem in the pipe...pump it up like a tire

  6. #6
    Vern's Avatar
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    Jerry, thanks, that is good to hear. I thought it was too coincidental that both SCs suddenly developed the same problems ... and that the higher boost brand new one developed exactly the same boost and same 'high boost, lower boost' routine ... If the clutches on both were bad, I would never achieve higher boost or higher rpms I imagine, so this does seem very much like a boost leak. Yes, Riva IC, no BOV, clamps all seem to be tight, I pulled my IC blockoff - I have the old PPG/RR style one that none of us could get to fit exactly right due to having to reuse a piece of the stock gasket. I put a good bead of Ultra Black on there when I assembled it, but I really would like a better one - do you have them in the store? I will check and order one ASAP if you do.

    Jawz, thanks, interesting idea, I can see where that would work well - it is hard to see/find leaks when they only happen at full throttle. Can you explain a little more on the 8 lb leak and 10 lb leak and where they were on your RXP? Was it just hose connections, or?

    I so wish somebody would make a replacement SC / IC pipe kit out of aluminum to replace the Riva plastic pipes. I think on the faster skis with more boost they tend to leak, get hot, so we tighten them up a little more, a little more, then sometimes they deform ...

  7. #7
    Moderator Franko's Avatar
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    Quote Originally Posted by Vern
    I so wish somebody would make a replacement SC / IC pipe kit out of aluminum to replace the Riva plastic pipes. I think on the faster skis with more boost they tend to leak, get hot, so we tighten them up a little more, a little more, then sometimes they deform ...
    Mark Underwood has made one. I have one on order because I melted the Riva pipe. In the mean time, I am using a metal pipe bent by a local muffler shop.

  8. #8
    Vern's Avatar
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    Franko, I have wondered about doing the same ... did you just have the muffler shop bend up some 2.5" pipe, or is it 2.75"? Did you have them crimp the ends, or just scuff it up real good and crank down the clamps? That would work fine for a season or until Mark gets his to market - the pipes should not really get wet or rust in this application, esp if only used for a month or two ...

  9. #9
    Moderator Franko's Avatar
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    They used 2.5 inch pipe and bent it like the Riva pipe. They did not crimp the end, but I would get them to do that if they have the ability. I have about 5 hours on it with no problems so far. That Riva pipe just could not tolerate 13.5 psi boost.

  10. #10
    Vern's Avatar
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    Thumbs up

    Got it, thanks for the input.
    Last edited by Vern; 07-31-2006 at 10:27 AM.

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