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  1. #1

    So whats your final answer?

    This seems like a catch 22, its been discussed several times but hasnt really been settled.

    It seems as though with the cat installed your top end #s can be higher.
    It seems as though with the SS installed your top end #s can be higher.

    but if you want the jetworks mod for better holeshot you need a D-plate and free flow exhaust.

    Are you guys picking one or the other top or bottom or is there a way to get both? I just removed my cat for inspection and it looked like new so I reinstalled. Mistake?


  2. #2
    HopatcongGPR's Avatar
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    yes, the cat and the sound supression installed will help get higher top rpm numbers.

    the catch, if the cat and or the sound supression is installed the backpressure increases. effectively increasing combustion temps.

    this is the main reason why people remove the cat and SS with 140-150psi compression. keep the piston crown/combustion temps in a "safer" zone. if tuned correctly, you can run the cat and the SS with 145+ compression.

    effectively, you could run higher compression to get a similar effect as the ss and the cat installed. ie., 155 compression with a free flow and d plate would probably give similar top end numbers as a 145psi boat with the cat and ss installed. however, the 155 psi boat will accelerate harder.

    i have seen a 30-40 rpm "consistent" gain by running with the ss. swap occured within 15 minutes of each other on my gpr.

    i run 150psi in my xll with the SS installed.

    i ran 155 in my gpr with the SS installed.

    both had /have a yamaha d plate installed.

    hope that helps.

  3. #3
    So basicly you make a choice between top or bottom as far as a jetworks mod goes, but with that aside you setup your exhaust for the compression your running.
    Has anyone done the jetworks mod without freeflow or D-plate?

  4. #4
    Chrisrokc's Avatar
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    Just the D-plate on mine added 50-100 rpms. Ski only had 20 hours on it or so.

  5. #5
    Happily Self-Employed WFO's Avatar
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    When I first started modifying my boat, I did one mod at a time to see the gains for each. I was running the freeflow and had tremendous bottom end. I put the stock SS back in and picked up 50rpms on top, but my bottom end suffered. Then I installed the Jetworks mod. My bottom end was back/equal to before and I had the 50rpms on top.

  6. #6
    Thats good info, so I actually dont need the free flow to install the jetworks? It just seemed like every place I read about it said I needed free flow. thanks.

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