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  1. #1

    RXT-X Air Intake Question

    Hi,

    I'm new to this site and I've been reading a lot of threads from all of you about your mods and I'm interested in doing a few now but I have a question since you all seem extremely knowledgable about what you're doing: Could anyone please tell me why you all make a 4" air intake vs. buying the 3" intake that Riva makes - is that one extra inch enough to make a noticeable difference? Not to sound stupid, but if the 4" is better, I would think that Riva would make one? Has anyone tested both and found positive results, if so I'd like to know where I could read the string.

    Thanks in advance for any help.


  2. #2
    Moderator Snoman's Avatar
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    First off let me say Welcome to Greenhulk!!!!!In a SCed engine you want to get as much fresh,cool air to the SC as possible.with the 3 inch Riva it is located fairly close to the motor taking in hot/warm engine air right to the SC...Plus its only 3 inches in diameter..Now with the 4 inch guys were running them up front away from the warm engine air...This does work..Now Riva has come up with a rear air intake that takes cool outside air and feeds it to the SC with less travel than a 4 inch front air intake..
    Depending on your riding conditions and style you would want to use a 4 inch front intake if you like to ride surf or rough conditions and if your a flat water rider than the Riva Rear Air is the way to go...

  3. #3
    Quote Originally Posted by Snoman View Post
    First off let me say Welcome to Greenhulk!!!!!In a SCed engine you want to get as much fresh,cool air to the SC as possible.with the 3 inch Riva it is located fairly close to the motor taking in hot/warm engine air right to the SC...Plus its only 3 inches in diameter..Now with the 4 inch guys were running them up front away from the warm engine air...This does work..Now Riva has come up with a rear air intake that takes cool outside air and feeds it to the SC with less travel than a 4 inch front air intake..
    Depending on your riding conditions and style you would want to use a 4 inch front intake if you like to ride surf or rough conditions and if your a flat water rider than the Riva Rear Air is the way to go...
    Thanks for your response, but from what I've read, I thought I can't use the rear air intake since my intercooler is in the way?

  4. #4
    Moderator Snoman's Avatar
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    No your right.On the x boats you have to buy an IC relocation kit.

  5. #5
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    After several trial/error intake systems by many people, a 4" setup is the most "bang for the buck" item you can have. And with this forum, which has been based on pushing the envelope on "outside the box" thinking, it fits right in...

    The 3" Riva setup is a system that had to be universal to all SC'd motors, going back to 2003 on the first SC'd ski, the GTX SC. Back then that was the only main option to get more air in. When this forum first started out as Blog by Jerry, he tried a 4" setup in the summer of 2005. Over time it has proved to be a simple yet VERY effective setup...

    AND do the math...calculate the total volume of a circle (pie * R-squared)cross section of a 3" and 4" setup, not counting length...

    3" intake = 7.065 sq/inches (3.14*1.5*1.5)
    4" intake = 12.56 sq/inches (2*2*3.14)

    Doing more math...

    7.065 = 100%
    7.065 * 2 = 14.13, or 200%

    12.56 / 14.13 = 88.8%

    Thats a volume increase of 88.8%

    Here is a 4" setup we installed on my father's RXT-X...
    http://greenhulk.net/forums/showthread.php?t=68048

    Combined with the removal of the Flame Arrestor from the Manifold, this was one of the best "bang for the $$$" modification you can do for this ski...


    --Danny

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