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  1. #1
    skigolfnut's Avatar
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    Chasing more speed/hole shot

    I did a test run yesterday with my new Venturi outlet with the largest ring 85mm installed
    I am going for hole shot for Closed Course racing, and best speed for the staight aways,

    Ski really jumps out of the hole on the starts now, and the shaft bearing carrier cleared up most of the cavitation issues nailing it from a dead stop

    I have the rotax racing ECU with the 8650 rev limiter, and was seeing top RPM at 8500 all day with a top speed now at 76 MPH

    what next?

    If I tweek the impeller to get it up to 8600 RPM would that get me a little more speed?

    If I put the smaller venturi on then, I loose hole shot, but gain more speed top end,


  2. #2
    Mothman's Avatar
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    Pitch for 8600 now, but you'll have to repitch to 8600 after summer heat takes it's toll.
    Stay with the 85. Heck, I use an 87. Pulls like a mule and still busts 80 at 3000ft.

  3. #3
    Moderator #985 lasportsmn's Avatar
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    glad to see you got your cavitation off the line figured out. That in itself will make you hard for any of the guys there to hang with.

  4. #4
    ou812's Avatar
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    Is that with a 3 blade?
    If so, Pitch for 8600 on the 85 ring now & then in the summer toss on an 87 ring to get some R's back (approx 100-120 R's)...
    Other option, Have a winter, spring pump/prop setup & a summer pump/prop setup to run the same 85 ring & be done with the guess work.

  5. #5
    skigolfnut's Avatar
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    Thanks everyone
    It is a 4 blade 15/20 -
    I am waiting on a ruling about what size injectors I can use and still run limited class, I am currently running stock bosch 42's with the ET-137 Wheel,
    would 48's give me more top speed?

  6. #6
    boost junkie skidoochris's Avatar
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    can you use a piggyback fuel controler?
    if you can the cmd will fine tune your fuel
    so at no boost your near 13 and at wot have the best afr too
    bigger injectors are no better than smaller ones if they keep correct afrs

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