Impeller Direction Pitch Down or Up for More Top Speed Based on Peak HP
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  1. #1
    Resident Guru zpilot's Avatar
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    Impeller Direction Pitch Down or Up for More Top Speed Based on Peak HP

    Very confused at what pitch direction to go from my current setup to achieve more top speed.

    My motor peaks 90-100hp @ 7300 rpm and i'm currently maxing at 6500 rpm. I'm running a big hub 10/18 swirl with great bottom/mid performance.

    Should I go down to a 9/17 to raise the RPM to get closer to peak HP/Speed or will I will benefit on the top by going up to a 11/19? I'm assuming peak HP would be the ideal target but not sure.





    1995 Kawasaki SC

    PJS Viper 9000 800cc
    PJS Exhaust Manifold
    Coffmans Full Exhaust
    Custom Jetinetics Flywheel/drilled ring gear
    12 Vein SS Magnum Pump
    10/18 Skat Track Swirl Impeller
    PJS Rip Turn
    DG Intake Grate






    1994 Kawasaki XIR
    Group K Head Mod
    PJS Exhaust
    Skat 9/17 Big Hub Swirl
    UMI Bars

  2. #2
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    Re: Impeller Direction Pitch Down or Up for More Top Speed Based on Peak HP

    go down and try to get closer to peak hp rpm.
    you'll gain in acceleration while keeping or hopefully increase top speed.

  3. #3
    PWCToday.com Is My Home Away From Home AC 46's Avatar
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    Re: Impeller Direction Pitch Down or Up for More Top Speed Based on Peak HP

    What ski? Z pilot
    R.I.P. Super Sic

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    PWCToday.com Is My Home Away From Home fastgtfairlane's Avatar
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    Re: Impeller Direction Pitch Down or Up for More Top Speed Based on Peak HP

    i believe hes talking about a super chicken
    91 440; PJS Viper 7000, jetsport exhaust mani, factory full pipe, coffman waterbox,solas 17*, jetco worked 440 pump, ocean pro nozzles. shredmaster ocean rideplate and grate combo, wide tray, footholds, deep strake mod, driveshaft fill,650sx quick turn

    build thread part 1: http://www.pwctoday.com/showthread.php?t=331343
    build thread part 2: http://www.pwctoday.com/showthread.php?t=364872
    build thread part 3: http://www.pwctoday.com/showthread.php?t=396154

  5. #5
    Resident Guru zpilot's Avatar
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    Re: Impeller Direction Pitch Down or Up for More Top Speed Based on Peak HP

    Thank you. Yes, the SC.

    I’ll try the 9/17 but now need to figure out if straight or swirl.





    1995 Kawasaki SC

    PJS Viper 9000 800cc
    PJS Exhaust Manifold
    Coffmans Full Exhaust
    Custom Jetinetics Flywheel/drilled ring gear
    12 Vein SS Magnum Pump
    10/18 Skat Track Swirl Impeller
    PJS Rip Turn
    DG Intake Grate






    1994 Kawasaki XIR
    Group K Head Mod
    PJS Exhaust
    Skat 9/17 Big Hub Swirl
    UMI Bars

  6. #6
    PWCToday.com Is My Home Away From Home Myself's Avatar
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    Re: Impeller Direction Pitch Down or Up for More Top Speed Based on Peak HP

    I agree with the above. The goal with impeller pitch is to get close enough to the target rpm without bouncing on it. A bit less pitch should get you there.
    http://www.facebook.com/twinlakesjetskirepair

    '89 Kawi 650SX 42.4 GPS
    +3" stock pipe, ported ex. manifold, drilled waterbox, blueprinted pump, Ocean Pro ride plate

    '99 Yama GP1200 65U 61.8 GPS
    ported cylinders, matched cases, milled head, blueprinted pump, long ride plate

    '96 Seadoo HX 717 53.13 GPS
    light porting, massaged cases, lightened flywheel, port matched manifolds, Rossier pipe, stubby pump cone

  7. #7
    Resident Guru zpilot's Avatar
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    Re: Impeller Direction Pitch Down or Up for More Top Speed Based on Peak HP

    Appreciate the feedback. I've read you can achieve up to 400 rpm pitching down so that should be much better. I can then start to play with pump reduction nozzle sizes to get a bit more and see how it performs then. Might even consider a custom 8/16.
    Last edited by zpilot; 02-16-2018 at 01:48 PM.





    1995 Kawasaki SC

    PJS Viper 9000 800cc
    PJS Exhaust Manifold
    Coffmans Full Exhaust
    Custom Jetinetics Flywheel/drilled ring gear
    12 Vein SS Magnum Pump
    10/18 Skat Track Swirl Impeller
    PJS Rip Turn
    DG Intake Grate






    1994 Kawasaki XIR
    Group K Head Mod
    PJS Exhaust
    Skat 9/17 Big Hub Swirl
    UMI Bars

  8. #8
    PWCToday.com Is My Home Away From Home theVetteman3's Avatar
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    Re: Impeller Direction Pitch Down or Up for More Top Speed Based on Peak HP

    Another thing to be mindful of is where that Coffmans pipe is making peak power vs the pipe that came on the skis with that pjs viper engine. Most of those wet pipes will be producing peak power somewhere around 6700-6800. Bill will know. He said the PJS EX 2650 was right around there.

    When doing unique conversions like this, I always find it's best to get a few impellers and swap them out and see how they compare. Definitely going down is the right direction though in this case.
    1985 JS550/800 "Pretty Red": Newmiller 800, Rhaas 750 pump conv. [56.3mph gps]
    2009 1100 SJ:
    Kawi 1100 build in progress
    2009 SJ MINT:
    KP steering adaptor, Worx 228 intake [45.8mph gps]
    1987 WJ650:
    6M6, JD Intake Grate, 17/20, cheater pipe [47.8mph gps]
    1994 XiR: 830cc Superstock, PJS side draft, 13/18 swirl [53.7mph gps]
    1998 SXI PRO:
    3DR hull mods [TBD]



  9. #9
    PWCToday.com Is My Home Away From Home wmazz's Avatar
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    Re: Impeller Direction Pitch Down or Up for More Top Speed Based on Peak HP

    Quote Originally Posted by theVetteman3 View Post
    Bill will know.
    Sorry I am late! I finally answered the PM.


    BM
    Horsepower == Speed, RPM != Speed



  10. #10
    PWCToday.com Is My Home Away From Home theVetteman3's Avatar
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    Re: Impeller Direction Pitch Down or Up for More Top Speed Based on Peak HP

    What were your thoughts Bill?

    Also Z do you know your current GPS speed? If I recall correctly, my xir with a factory pipe and a 9/17 straight impeller did about 47-48mph GPS. The SC has more hull wetted area but similar weight. Engine and pipe combo produces lower peak power than what you're pulling, but it did allow the engine to rev out nicely.
    1985 JS550/800 "Pretty Red": Newmiller 800, Rhaas 750 pump conv. [56.3mph gps]
    2009 1100 SJ:
    Kawi 1100 build in progress
    2009 SJ MINT:
    KP steering adaptor, Worx 228 intake [45.8mph gps]
    1987 WJ650:
    6M6, JD Intake Grate, 17/20, cheater pipe [47.8mph gps]
    1994 XiR: 830cc Superstock, PJS side draft, 13/18 swirl [53.7mph gps]
    1998 SXI PRO:
    3DR hull mods [TBD]



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