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  1. #1
    Stef01885's Avatar
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    Cool Impeller FZS SVHO question

    Hi all,

    Looking to repitch my solas 13/20 impeller but wanted some advice if possible. I ride my ski solely on the sea and due to the UK sea NEVER being flat I struggle to reach speeds over 65mph.

    As a result I'm pretty sure I'm missing out on some acceleration with my current impeller.

    Would I be ok to drop to a 13/18? I dont want to be constantly bouncing off the limiter, im happy if I can reach 70mph without over revving constantly.

    Current mods are
    Power filter
    Ribbon delete
    Tj exhaust
    Riva bov
    13/20 solas
    Breather filter
    SCOM

    Ski is a 2014 FZS SVHO.

    Will I be OK to drop to a 13/18?

    Thanks in advance.

  2. #2
    Stef01885's Avatar
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    can anyone help?

  3. #3
    Click avatar for tech links/info K447's Avatar
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    Quote Originally Posted by Stef01885 View Post
    ... I ride my ski solely on the sea and due to the UK sea NEVER being flat I struggle to reach speeds over 65mph.

    As a result I'm pretty sure I'm missing out on some acceleration with my current impeller.

    Would I be ok to drop to a 13/18? I dont want to be constantly bouncing off the limiter, im happy if I can reach 70mph without over revving constantly.

    Current mods are
    Power filter
    Ribbon delete
    ...
    Riva bov
    13/20 solas
    ...
    SCOM

    Ski is a 2014 FZS SVHO.

    Will I be OK to drop to a 13/18?
    ...
    You want to run 70mph in water that is never flat, or you want to do 70mph when the water just happens to be smooth for a few lucky moments?

    In addition to greater top speed, you want more acceleration.

    On smooth water what is the sustained maximum RPM you are seeing?

    What tune is in the ECU currently?

    If you have (or were to change to) an aftermarket tune, what is the best fuel octane you have available?
    What gasoline octane are you currently using?

  4. #4
    Stef01885's Avatar
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    As long as I could touch 70 when the sea just happens to be flat then yeah i'd be happy, as it's a very rare occasion. My understanding is that by de-pitching my impeller i'd see improved acceleration but reduced top speed so as i barely reach anywhere near top speed in the sea, I thought i'd be best to de-pitch and make the most of the added acceleration.

    No tune at the moment, just SCOM to stop the speed limiter kicking in (no plans to add a tune)

    Unsure on current rpm (I have a tiny tach installed but haven't had chance to use the ski just yet)

    95(UK) octane.

    thanks

  5. #5
    Click avatar for tech links/info K447's Avatar
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    Quote Originally Posted by Stef01885 View Post
    ... touch 70 when the sea just happens to be flat ...

    My understanding is that by de-pitching my impeller ...

    No tune at the moment, just SCOM to stop the speed limiter kicking in (no plans to add a tune)

    Unsure on current rpm (I have a tiny tach installed but haven't had chance to use the ski just yet)

    95(UK) octane.
    ...
    You need to establish what RPM the engine is currently turning at WOT on smooth water. That will tell you how close you are to the stock RPM limiter.

    A Riva MaptunerX tune for your 95 RON fuel octane might give you enough of a power boost to turn the current impeller harder and get your speed up. Mid-range acceleration should also improve.

    Or perhaps switch to a slightly less pitch Solas impeller and let the Riva tune spin the engine maximum RPM higher than stock.

    I am not an expert on the FZ hull - is there an aftermarket intake grate that would help you with rough water jet pump hook-up?

  6. #6
    Site Admin Green Hulk's Avatar
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    Quote Originally Posted by Stef01885 View Post

    No tune at the moment, just SCOM to stop the speed limiter kicking in (no plans to add a tune)
    Then you need to stay with the 13/20 pitch. The 13/18 would just put your engine running hard on the limiter which will reduce speed. In your cooler UK water and climate, you may very well be on the limiter now with the 13/20 and may need to add some pitch.

  7. #7
    Stef01885's Avatar
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    Quote Originally Posted by Green Hulk View Post
    Then you need to stay with the 13/20 pitch. The 13/18 would just put your engine running hard on the limiter which will reduce speed. In your cooler UK water and climate, you may very well be on the limiter now with the 13/20 and may need to add some pitch.
    Thanks for the info, would a tune make a noticeable difference, even on rough sea? I presume if I added a tune I could then look at dropping to a 13/19 or 13/18 to make use of the raised rev limit?

  8. #8
    Click avatar for tech links/info K447's Avatar
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    Quote Originally Posted by Stef01885 View Post
    ... would a tune make a noticeable difference, even on rough sea?

    I presume if I added a tune I could then look at dropping to a 13/19 or 13/18 to make use of the raised rev limit?
    How much ‘more’ depends on the tune, but typically with the same impeller and an aftermarket tune you are going to get more power from the engine, compared to a stock tune. Across the RPM range.

    More engine power means the engine can twist the impeller more forcefully, which means the peak sustained RPM can be higher. More impeller RPM means more thrust, and more thrust means more top speed. All this with the same impeller.

    Since the RPM limit is (typically) set somewhat higher with an aftermarket tune, the ECU will not see a reason to back off the power at wide open throttle.

    In general (rule of thumb sort of guide) every additional 100 RPM translates to about 1mph more top speed. There are lots of factors involved.

    With the optimal (for your fuel) tune installed, you then also reduce the impeller pitch, that will allow the SVHO engine to rev even higher, sustained. How much higher, and whether you even want it spinning that fast, depends on where your RPM is currently with the stock tune and how much RPM you gained just from the tune.

    Your riding conditions are different from many riders on here who hunt for speed but mostly riding in smooth to moderately rough conditions. I suspect your typical water is rougher than many here would encounter regularly.

    A tune along with optimizations for rough water may provide real improvements in your overall riding experience. You may already have the right impeller.

    Improving your rough water hook-up - consider intake grate options and perhaps the Lucky13 tail cone. Others who know the FZ hull and rough water may be able to suggest other ways to make it even better in the rough.


  9. #9
    Saum700p's Avatar
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    I would have it trued and pitched possibly around 13/21. There is also the lucky 13 cone option to up the rear pressure.

  10. #10
    Site Admin Green Hulk's Avatar
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    Quote Originally Posted by Stef01885 View Post
    Thanks for the info, would a tune make a noticeable difference, even on rough sea? I presume if I added a tune I could then look at dropping to a 13/19 or 13/18 to make use of the raised rev limit?
    Going with a MaptunerX tune is what I would do. Lots more performance this way and you can continue to run your 13/20 with a stage 1, or stage 1 plus tune.
    I would do a 13/18 with a stage 2 or 3 tune.


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