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  1. #11
    PWCToday.com Is My Home Away From Home wmazz's Avatar
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    Re: PJS full pipe RPM range?

    Quote Originally Posted by jevindack View Post
    dude wanted to know what the rpm range is on this pipe.
    That isn't relevant. Your pump and impeller determines peak rpm because it
    acts like a rev-limiter. Jet Skis do not act like other two-stroke MX, Quads,
    or (maybe) snowmobiles. There is normally only a few hundred rpm of over-rev
    past peak hp, and that only occurs if the pump is set-up properly.

    I have installed many of those pipes, but I have never measured one, so I
    don't know where peak HP occurs for a given exhaust port timing.

    In the past, all the early PJS 440/550 were too short (JUNK) but the 440
    pump is more forgiving than other Kawasaki pumps. The 550 pump is less
    forgiving.

    If the 550 pump locks up at a lower rpm than where peak HP occurs, it will
    create a greater load on the engine, and that load will increase combustion
    temps.

    The limited pipe was a good suggestion, it is based on my 550 pipe, and produces
    peak HP @7000 rpm with stock exhaust ports. With raised exhaust ports ~180'
    the peak HP will occur @ ~7450rpm. (Your pipe is much shorter than the limited
    pipe)

    If you want to know the approximate peak HP rpm of that pipe, measure the
    center line length of the chamber only, to the end of the rear cone. I know
    the lengths of the other parts. It is helpful to use a 1/4" wide tape measure
    (~1 yard/1 meter), and it is easiest if you use mm's instead of inches. The
    accuracy of your measurement will determine how accurate the peak HP
    approximation is.


    Bill M.

    Please do not measure the stinger length, or try to calculate the 1/2 rear
    cone length.

    I am fairly certain the head pipes centerline length is 225mm's, if not please
    provide a more accurate length.
    Last edited by wmazz; 12-03-2018 at 02:47 PM.
    Horsepower == Speed, RPM != Speed



  2. #12
    PWCToday Regular jevindack's Avatar
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    Re: PJS full pipe RPM range?

    Honestly I would rather use my Coffman half pipe for this set up, I think the pipe and rpm range I will be set up at would work great with a Coffman half pipe. The only reason I’m leaning away from the half pipe is because it will be a lot harder to control how much water is moving though the motor and through the pipe. I know with that PJS pipe I can set up how much water goes through it. With the half pipe I’m really limited on doing that.

  3. #13
    PWCToday.com Is My Home Away From Home fastgtfairlane's Avatar
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    Re: PJS full pipe RPM range?

    the half pipe water tuning isnt any different than the pjs full pipe. just different. the only pipe that is technically tunable anyways was the factory full pipe with adjustable water bleeds. you could run dual cooling, one for the engine and one for the pipe. take the head water outlet and run to a pisser, your other line will go where the head outlet fed the pipe. then where the outlet is, run a tee with bypass and flow control valve going to the stinger. what impeller pitch are you planning to run?
    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

  4. #14
    PWCToday Regular jevindack's Avatar
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    Re: PJS full pipe RPM range?

    Fastgt I think that would be the ticket for this set up. I have a skat 15.5 now and a scat 16. I think the 16 would be the way to go

  5. #15
    PWCToday.com Is My Home Away From Home fastgtfairlane's Avatar
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    Re: PJS full pipe RPM range?

    impeller pitch will vary depending on what you are using for an outlet nozzle diameter. larger diameter, the taller impeller pitch you can get away with. i had a fully freestyle ported reed engine with dual sbn 38s, 100 octane fuel, factory full pipe and was running a js550 pump with a 69mm outlet nozzle, jrd stubby pump cone (dont recommend) and a 11.5/16 pitched skat. i was running the lower pitch to help with bottom end as i was running a full pipe with the 550 pump. the porting was still with the stock exhaust port timing, just widened exhaust ports and raised transfers to reduce the blow down timing to get more bottom end.
    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

  6. #16
    Resident Guru BU1LD's Avatar
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    Re: PJS full pipe RPM range?

    Have you got any pics of your build?


    VintageJetSki.com



    • JS 400 Original 1973,umber 414
    • JS 440 Stock
    • PJS 550 - Fully blown race engine! Built by Ed Miller

  7. #17
    PWCToday Regular jevindack's Avatar
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    Re: PJS full pipe RPM range?


  8. #18
    PWCToday Regular jevindack's Avatar
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    Re: PJS full pipe RPM range?

    B94B2096-039F-4480-8AE7-8275A6A11A9A.jpeg

    That’s all I have right now

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