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  1. #1
    JFizzleJR's Avatar
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    Performance is Down..Need Suggestions

    Just got back from the lakehouse.. 3 weeks ago I took my RXP out for the first time since the mods. I achieved 72.9 in chop and it was about 10 secs of WOT..A lot of porpoising. Since then I have put on custom OPAS blockoffs that stopped the porpoising. I went up to the lakehouse (1300ft elevation) and could only pull off 71's.. Rpms only dropped 100 and it's the first time I've gotten to test without bouncing up and down.

    I am expecting about 74-76 with my mods and I can't figure out what's wrong. The only theory I have come up with is I'm over propped. Although I can't see how because I'm spinning 8000 rpms with this out of the box 15/19r.

    I've got the Riva grate, 4" custom front intake, rotax high boost sc impeller, metal washers, SS wear ring, 81mm ring, 15/19r 3 blade, xs ic, rideplate holes filled, 2° wedge, vts extension rod, and the reverse bucket chopped.

    I got new plugs to put in but they aren't threaded like they're supposed to be. I never knew NGK would make the same model and have one not threaded and one threaded. And I know I got the correct part # too .
    Fuel is good also, 93 octane.

    Any suggestions on finding the speed would be great. I'm really lost on this one since I'm spinning 8000 rpms.


  2. #2
    Moderator Snoman's Avatar
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    What kinda injectors are you running..From what your listing in mods it looks like you still have the stock injectors..If You are still running stock injectors you need to go to the 42# injectors..probley were your performance lose is

  3. #3
    JFizzleJR's Avatar
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    Sorry I forgot to put that I had the injectors. These mod lists get so damn long these days

    I've got the rotax racing 42# injectors installed.

    The only thing I've added since the last time out are the OPAS blockoffs. In my mind there's no way they could be the problem. I forgot to take pics of them again

  4. #4
    BMW FTW Yellow04RXP's Avatar
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    If you are turning good rpm then the only place to really look for the slow speed would be the pump....you might have bent the prop

  5. #5
    did the lake temp & air temp rise the wamer it gets the less power u'll produce if ur r's have drop off u'll haft 2 repitch ur prop or go 2 a 82mm ring right now i have a 82 in my ski turing 8400 water at 78 air 87 last week i was turing 8450 a& bouncing off the rev limter water 69 air i think around 78 withe the 82 ring

  6. #6
    JFizzleJR's Avatar
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    The temps were close enough to not have a significant effect. I was running 8100 strong at sea level so the 8000 rpms was expected when going up 1300 ft. in elevation.

    What I am trying to get at is I had 72.9 in poor conditions. I expected much more on good conditions. Now I cannot even hit 72 with porpoising stopped and glass water. This is an 05 rxp by the way, stock ecu too.

    I'm going to try a 15/20r if I can find one and if nothing changes I'm going to take the OPAS blockoffs off. Thanks for your thoughts guys. This is an enigma to me because the RPMs are there but the performance is not.

  7. #7
    JFizzleJR's Avatar
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    Quote Originally Posted by Yellow04RXP View Post
    If you are turning good rpm then the only place to really look for the slow speed would be the pump....you might have bent the prop
    Prop is untouched. Accel is great and there's no cavitation.

  8. #8
    Water4fire's Avatar
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    Maybe Heat soak and the 100r's is it.

    But I am scratching my head also as my 06 RXP with Just the RR high boost impeller, 4inch rear intake and 15-20R depitched a little hit 73.8 with all the time mid 73's.

    HMMM:.

  9. #9
    JFizzleJR's Avatar
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    Can't be heat soak either Warmed it up for 10 mins then took 2 WOT runs. 71.2 and 71.6. Temps were 68° air and 66° water. I've got a 15/20r that I sold coming back to me so I'll see if the problem is the 15/19R.

  10. #10
    Water4fire's Avatar
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    Did you check for water leaks in the IC?

    I pressure tested both my XS IC before use. They are cheap IC's so
    maybe??? Also look for a Boost leak maybe. Have a gauge? Makes cheaking boost leaks easy.

    Also Slipping clutch? Just some thoughts.

    .

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