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  1. #1

    General Question from a newbie

    Okay,

    I'm a car guy. So I'm very mechanically inclined.

    My question is....

    Why doesn't Seadoo go with a positive displacement blower?

    They're much better than cetrifugal blowers in just about every category (the only exception being price).

    I truly do not understand why you'd need a clutch on the blower as well. The only time I've ever seen that done on a car was Mad Max Road Warrior and it kinda looked like some movie mythology.

    Positive displacement blowers are generally more efficient than centri's, have lower intake temps (not that it matters with a water/water exchanger), have much better torque and power curves.

    In the auto world, the turbo is king nowadays (with all the new management technology....there's really no such thing as turbo lag anymore and their much more efficient than superchargers) and I understand why their not desired in a marine environment (salt water corrosion of the exhaust/turbos).....

    When is Seadoo going to dump the centri and get a twin screw....or even a roots?


  2. #2
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  3. #3
    A.they're a pita to plumb in the tight space provided

    B. Heat differences are enormous. Turbos raise engine bay temps easily over 30 degrees when compared to a s/c application, which doesn't bode well in the near sealed environment of a pwc engine hole.

    C. Honda did go the turbo route with their pwc lines. Most modern units are closed cooling loops so salt water isnt really a big issue anymore.

    D. I believe the new kawasaki 250x (250hp) does use a roots style s/c.


    E. Remember with props you have a constant load on the drive train, which would inturn mean the turbo is under constant load...turbos don't like being under constant load, then tend to boil oil and cook bearings.

    F. Just boils down to the mfg choice. Just like with cars some like s/c applications some like turbo setups.

    It should be noted my comments are mainly based on my extensive experience with automotive backgrounds and applying that to my limited knowledge of marine platforms.

    -John
    Airflow Logistics - We specialize in Mazda/Porsche/Jeep engine management

  4. #4
    Quote Originally Posted by Fatty View Post
    Okay,

    I'm a car guy. So I'm very mechanically inclined.

    My question is....

    Why doesn't Seadoo go with a positive displacement blower?
    Price price and more price...

    They're much better than cetrifugal blowers in just about every category (the only exception being price).
    Roots blowers are limited in boost for the size you`d need to fit in the hull. pulley ratio`s or gear drive ratio`s can be played with. Heat would be a concern also.
    I truly do not understand why you'd need a clutch on the blower as well. The only time I've ever seen that done on a car was Mad Max Road Warrior and it kinda looked like some movie mythology.
    the clutch is for a moment of slip when the craft becomes unhooked and re-hooked being the SC is gear driven. the shockloads are enough to snap the shaft if it weren`t designed to slip.

    Positive displacement blowers are generally more efficient than centri's, have lower intake temps (not that it matters with a water/water exchanger), have much better torque and power curves.
    agreed, I personally like the appearances of the roots type, I`m old school!...

    In the auto world, the turbo is king nowadays (with all the new management technology....there's really no such thing as turbo lag anymore and their much more efficient than superchargers) and I understand why their not desired in a marine environment (salt water corrosion of the exhaust/turbos).....
    agreed again, I had a 06 VW MK5, balls ass fast from the line...

    When is Seadoo going to dump the centri and get a twin screw....or even a roots?
    prolly never since they haven`t even made the clutch system any more reliable...
    Mad Max movie: that is trick film stuff, you know you can`t get any RPM`s when the blower is not spinning, tight clearances between rotors won`t allow enough air fuel... I get a kick out of that part of the movies when Mel pulls up the red knob! ... is it an AC clutch set up, don`t think that`ll handle the torque loads either, maybe they could use a SeaDoo cluth set up instead!... ...PR...

  5. #5
    Quote Originally Posted by Fatty View Post
    Okay,

    I'm a car guy. So I'm very mechanically inclined.

    My question is....

    Why doesn't Seadoo go with a positive displacement blower? They're much better than cetrifugal blowers in just about every category (the only exception being price).
    Like you said, $$$. We have found the Centri's to be great when going for top speed. We've run 90+mph on them, but are now starting to swap them out for its close cousin the turbo.

    I truly do not understand why you'd need a clutch on the blower as well. The only time I've ever seen that done on a car was Mad Max Road Warrior and it kinda looked like some movie mythology.
    You need the clutch when you come unhooked or your SC will go BOOM!!!

    Positive displacement blowers are generally more efficient than centri's, have lower intake temps (not that it matters with a water/water exchanger), have much better torque and power curves.
    Roots charger torque curve falls off at high RPM. Roots don't mean crap anyways in this platform. We are at peak RPM almost instantly anyways, so even a centri is at full boost very quickly. Twin screw would be the way to go if you want to stick with the SC platform but very $$$.

    In the auto world, the turbo is king nowadays (with all the new management technology....there's really no such thing as turbo lag anymore and their much more efficient than superchargers) and I understand why their not desired in a marine environment (salt water corrosion of the exhaust/turbos).....
    There is a turbo kit out for the RXP now. Capable of 40psi of boost and 450+HP when hooked up correctly to allow for it'sfull potential. JD1 has it and ran a 94.5mph at MB3 this year before his ski broke down.

    When is Seadoo going to dump the centri and get a twin screw....or even a roots?
    Roots sucks for top speed. Their torque curve falls off. Phuck roots, go twin screw if you want that route. Centri's are better for top end unlike roots.
    And check out this chart. I'm sure you're very familiar with it, but it applies more to cars than skis.

    http://www.coloradocobras.com/whippl...son-chart.html

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