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  1. #1
    landwarrior's Avatar
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    Rear Exhaust / Through Hull Exhaust - Performance Gains / Tune Requirements?

    Forum newbie here...

    First off thanks to so many of you for not only completing all the R&D you do here, but also taking the time to report back in explicit detail helping all of us out there.

    I've officially sold my old girls, and upgrading to some real machines this winter, starting with the GP1800 in in a few short weeks.

    I do not see much info on rear exhaust setups, and I have a couple specific questions.

    1. Are their performance gains moving to a rear exhaust/through hull exhaust setup vs. the standard free flow mod, and using the stock exhaust port?
    2. Is there a separate tune requirement when moving to a rear exhaust setup/through hull exhaust vs. the standard free using the stock exhaust port?
    I'm currently only seeing feedback supporting personal sound preference, but I'm not seeing a lot of feedback surrounding this specific mod comparison directly related to performance.

    Thanks in advance,
    Mark


  2. #2
    Site Admin Green Hulk's Avatar
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    A rear exhaust is not currently available for the GP, but Riva will release one soon.

    There are no gains with a rear exhaust, you do it for the sound
    Plus, it cleans up the inside of the hull a lot.

    being there are no gains, it doesn't change the tune requirements.

  3. #3
    VdeKock's Avatar
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    Good question... And if you ad the Riva Waterbox with the rear exhaust?

    thx

  4. #4
    Site Admin Green Hulk's Avatar
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    Quote Originally Posted by VdeKock View Post
    Good question... And if you ad the Riva Waterbox with the rear exhaust?

    thx
    i have never seen the waterbox change the tuning requirements either. It does make for an incredible sounding ski. The best sounding ski I ever had was a VXR with riva waterbox and rear exhaust.

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  6. #5
    svhokid's Avatar
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    i had free flow. sounded good cruising not much different than stock but very droney at no wake speeds. then did a thru hull. sounded really good but not loud enough for me. paired with a riva waterbox it sounds amazing . i love it. didnt notice much performance gains but i can imagine the waterbox gets emptied out quicker than a stock one

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  8. #6
    wilsonma's Avatar
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    Quote Originally Posted by svhokid View Post
    i had free flow. sounded good cruising not much different than stock but very droney at no wake speeds. then did a thru hull. sounded really good but not loud enough for me. paired with a riva waterbox it sounds amazing . i love it. didnt notice much performance gains but i can imagine the waterbox gets emptied out quicker than a stock one
    What about drone with the rear exhaust Thru hull compared to just free flow exhaust exiting in the tunnel?

  9. #7
    VdeKock's Avatar
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    Quote Originally Posted by svhokid View Post
    i had free flow. sounded good cruising not much different than stock but very droney at no wake speeds. then did a thru hull. sounded really good but not loud enough for me. paired with a riva waterbox it sounds amazing . i love it. didnt notice much performance gains but i can imagine the waterbox gets emptied out quicker than a stock one
    Nice... I have the rear exhaust. And just bought the Riva water box from rcab85

  10. #8
    svhokid's Avatar
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    Quote Originally Posted by wilsonma View Post
    What about drone with the rear exhaust Thru hull compared to just free flow exhaust exiting in the tunnel?
    the free flow drone is hard to explain its like an echo or or something and the rear exit just sounds like an exhaust (way crisper then freeflow)

  11. #9
    I had the riva thru hull exhaust and the riva waterbox On my heavy modded yamaha fxsho and the sound was crazy perfect !

    I contacted Deans team About the riva waterbox in combination with the thru hull exhaust for the GP 1800. They advice me to use the stock waterbox if I keep the stock SC for the best results . Only when I upgrade the SC the riva waterbox is a good option.

    Anybody who knows why this is ? Because I really love the sound of the riva waterbox in combination with the thru hull exhaust, but if its bad for the performance, i only take the thru hull exhaust.

  12. #10
    Site Admin Green Hulk's Avatar
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    Quote Originally Posted by Dirtybig View Post

    Anybody who knows why this is ? Because I really love the sound of the riva waterbox in combination with the thru hull exhaust, but if its bad for the performance, i only take the thru hull exhaust.
    It will not hurt the performance at all. It's just not a necessity to have the waterbox with few mods. For those with a higher level of mods and turning really high RPM then the waterbox becomes a necessity and will give a power gain.

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