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Thread: free speed?

  1. #1

    free speed?


    So I have this idea, please hear me out.

    Kawasaki ski's came with the KAIS.... Kawasaki Air Induction System i could not find much on the the system or pictures other then the fact that somewhere along the bottom of the hull after the jet intake, there are holes drilled connected to hoses. When the ski is at high speed low pressure forms at those holes and air is sucked through to the bottom of the hull, forming bubbles and reducing the friction of the ski. The hoses are there to prevent the holes from filling the hull with water when the ski isnt moving. They came on the ZXi's and other ski's that Kawasaki made.

    Now im gonna research this a whole lot more. but it seems to me that Kawasaki took the idea from supercavitating propellors, and those russian torpedos that travelled super fast underwater using airjets ahead of them to break the water up. Seems to me that if a MAJOR jetski manufacturer thought it was a usable idea... as does the russian military and many other large engineering companies, why couldnt we put it to good use?

    Now here is my idea. I want to install this onto my YAMAHA jetski.

    Instead of looking for the impossible (for one man with no test tank) to find low pressure points under my hull. Why wouldn't I just FORCE air under there with pressure.

    And while I am at it... why bother installing an air pump to rob power from my engine, ect... why wouldnt I just use the unlimited source of high pressure air that already is making my jetski move.... the engine. Yes I want to use the exhaust from my engine, to force bubbles under my ski, to lower the friction to go faster.

    thoughts? am I crazy?

  2. #2
    mrbtd's Avatar
    Join Date
    Jul 2005
    Lindenhurst, Illinois, United States
    you want as much clean water in front of the grate as you can get. If you did something to the back all you would do is lift the back of the ski. You need the front lifted to go faster.

  3. #3
    mudslanger's Avatar
    Join Date
    Jul 2010
    Huntsville Al

    air holes

    sounds like in theory it could work, i dont thikn i would restrict my exhaust to do it tho. an air pump sounds better but it seems like you would have to put a lot of little holes and tubes in the pump shoe and ride plate to get the air under there kind of like an air hockey table works, if you just try a couple of big tubes it would have to suck the air in there between the hull and the water not likely the pressure of the hull pushing against the water wouldnt let the air under there. i think if i was going to try this i would drill a lot of little holes on angle with a bunch of little hoses and air pump. someone should try this id like to know if it works.

  4. #4
    Quote Originally Posted by mrbtd View Post
    you want as much clean water in front of the grate as you can get. If you did something to the back all you would do is lift the back of the ski. You need the front lifted to go faster.
    this is not about LIFTING the ski, this about reducing friction of the part of the ski touching the water.

    air is a hell of alot slipperier then water.

    And seriously... i would never intentionally employ an exhaust restriction to do this work... im not retarded. has anyone ever actually measured the exhaust backpressure before the waterbox?

    you do not need much pressure to start bubbling under water of less then 1 foot deep, aquarium pumps do this all the time.

    If you measure the exhaust backpressure before the waterbox, you will see its often about 0.5 to 1psi. thats more then enough pressure to start bubbling. all you really have to do is then run the bottom hull bubblers in parallel with the standard issue exhaust system on the ski and you should net enough gas under there to get some sort of effect.

    and yes... OBVIOUSLY i am going to seek out a zxi or something similar and see how they did it but im not dumb enough to force air into the jetpump intake.... gah.

  5. #5

    very interesting... and since i happen to be in tokyo for the next 2 weeks, i am gonna go visit this kodama and see what i can learn!

    glad to see im not the only person who beleives this can and will work! muahahah.... why make more power when you can make less drag!

  6. #6
    learned quite a bit about this today online... looks like if you know how to setup your ride plate effectively, you already are 1/4 the way to utilizing supercavitation in drag reduction... however this only occurs on your rideplate area. alot of this seems very counter intuitive until you know what is going on with the airflow and such.

    seems to me that if you can even reduce the drag in the rideplate area by 15% that is a huge step forward.

    however for it to correctly work you do need to have a clean edge on the hull before the rideplate. this does explain alittle here and there about why yamaha did certain things in its waverunner design, even if they are not intentional it benefits SCH (super cavitating hull) design in the area around the rideplate.

    looks like this could easily be adapted on my gp1200 without even having an airpump or hoses or anything. i'm going to do a bit more research before i repost here with pictures ect. but i do recommend people download and read this pdf, the online google version sucks in comparison, use the link at the top.

  7. #7
    Moderator beerdart's Avatar
    Join Date
    Aug 2006
    Cool idea very interested in how it turns out.

  8. #8
    GoFastGuru's Avatar
    Join Date
    Jul 2010
    guntersville Ala
    talk to jim about your ride plate there is alot of that already been done .

  9. #9
    Quote Originally Posted by GoFastGuru View Post
    talk to jim about your ride plate there is alot of that already been done .
    what exactly do you mean when you say "there is alot of that already been done"

    AFAIK nobody has really looked deeply into this regarding jetski's except for Kawasaki itself. Most of my searches come up dry on here and x-h2o and pwctoday, with minimal things except for people modding the KAIS hoses slightly as a claimed improvement.

    additionally if there is alot of work on this it must then be well hidden or unspoken by tuners in regards to keeping money in their pocket... which is a lame excuse because you'd think the racing scene would be all over this.

    considering my ski directly, i have just about everybody's plate through my hands and not once have i ever come across any design that seemed to take these principals into account, despite how easy it is to adapt.
    Yamaha stock, Riva, R&D, Protec, and shredmaster all utilize the same hydrodynamic principals in their plates, their designs only vary by length, angle and configuration... hell even the GroupK plate is basically an R&D unit cut to not have a cast like shit appearance and provide more nose lift.

    What we wanna do is alter the plate's configuration, and angle, along with the hull's shape just prior to the rideplate in an effort to provide a zone of low pressure. This zone of low pressure will then force the large amount of air that is inside the jetpump/transom area to be sucked under the rideplate, mixing with the water that is under the rideplate and reducing friction.

    Anyways, I will stand by my word and post up more information once i get it and pictures ect...

  10. #10
    mudslanger's Avatar
    Join Date
    Jul 2010
    Huntsville Al
    you should search out the old post about air under the rideplate. like gofastguru said thats already been done. you just have to do a lot of research and im pretty sure the guy that done it didnt use exaust or a pump. but i still like my idea on it i may try it on the old stock plate i pulled off my 1300 just for the heck of it. thanks for refreshing an old idea.

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