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  1. #1
    Jared of Oklahoma
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    Confused about Dry pipes and water boxes

    To start out with this stuff will be going on my 1994 SLT750


    OK I bought a stock Dry Pipe (from a 1992 Polaris) and a DG Tri-Oval water box recently from another member. I have researched the pipe in the factory manual posted on this site. and to be honest I do not understand what makes it a dry pipe. In the manual it still shows the inlet and outlet for water flow so how can it be dry? and I could not find anything in the Factory or Clymers manual that describes it as a dry pipe. or am I misunderstanding what makes a pipe dry??

    and also is there anything on here I can read that explains the theory behind what a dry pipe will do to increase performance?? and where does the water box come in? I assume for back pressure...


  2. #2
    Moderator beerdart's Avatar
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    Please post a pic of the pipe..

    A dry pipe introduces water at the outlet and a wet pipe introduces water up near the cylinder outlet. The theory is that a dry pipe will run hotter and change the sonics in the pipe. The hotter you get the pipe the better the sonic wave is for higher RPM's.. (Clear as mud???? )

  3. #3
    Jared of Oklahoma
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    thanks for an explanation

    Quote Originally Posted by beerdart View Post
    Please post a pic of the pipe..

    A dry pipe introduces water at the outlet and a wet pipe introduces water up near the cylinder outlet. The theory is that a dry pipe will run hotter and change the sonics in the pipe. The hotter you get the pipe the better the sonic wave is for higher RPM's.. (Clear as mud???? )
    I will have to post the pic tomorrow cuz the pipe is in the storage box on one of my doubles at the shop.

    sounds allot like some of the jet engine theory I learned years ago. So in a sense yes it does make sense why it would increase performance. Surely higher RPMs translate into a faster ski. I'm just not one of those "Blind Sheep" who just does exactly what everyone else does to get a faster ski. although I will say it is extremely nice to have a path to follow. As in you and Xlint, and Keddano, and several others I respect as well on this web site with your tales of the skis you have built and what you have done to them to make them scoot. I like to understand why things do what they do and how it affects other things. The more I learn from you Wizards the better off I am. and then I can also help people out on this site.

  4. #4
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    A dry pipe will still have water cooling it. Otherwise it will get real hot under the seat and cause damage/burn you. Both styles are essentially a pipe within a pipe.

    A dry pipe only injects water at the exit of the exhaust pipe to cool the rubber coupler and waterbox. This helps to keep the exh gases hot and helps in the upper RPM band. (more top end)

    A wet pipe injects water into the exhaust stream about half way up the pipe. This cools the gases and changes the resonance like BD mentioned. Wet pipes are good for bottom end power because of this.

    Now you can have best of both worlds if you install a water injection unit into a dry pipe, like the MSD brand. This will give you water injection for bottom end, and stop injecting at you predetermined RPM and run dry from then up in the RPM for top speed.

    Waterboxes are nothing more than a muffler. Not so much as back pressure, but water holding tank. A stock box is large (and quiet), while the aftermarket are smaller in size (louder). When you nail the throttle, all the water that filled the waterbox from idling, low speed, etc needs to be expelled before the exhaust will flow freely.

    So a smaller box will hold less water and gain in accel because it has less water to remove than stock.

    A jet works valve is very similar in theory. The jet works valve will halt water flow into the waterbox when idling to prevent the box from filling up. (same reason as above) Now it will be forced open when jet pump pressure increases from accelerating to cool the exh parts. This again improves accel by not having to expel water from the waterbox before it can flow freely.

    Hope this helps.

  5. #5
    thesepaperwings's Avatar
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    The dry pipe is a long dry pipe. It will give the same max rpms as a wet pipe but will allow you to run a steeper pitch on the lower end of your impeller.

  6. #6
    thesepaperwings's Avatar
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    SHHH.........look what I found.......
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  7. #7
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Quote Originally Posted by thesepaperwings View Post
    The dry pipe is a long dry pipe. It will give the same max rpms as a wet pipe but will allow you to run a steeper pitch on the lower end of your impeller.
    Where did you find that info?


    And is that another set of triples or the same set Jonjon scored?

  8. #8
    thesepaperwings's Avatar
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    The stand up gurus explained it to me. They deal more with pipes then anyone. I'll find the thread.

    These are a set of tripples that someone is trying to sell, well at least he was a month ago but I'm not sure if they sold or not.

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