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  1. #1
    Pistonwash's Avatar
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    Concerning intake manifolds

    This was taken off a Japanese website where a jetski tuner has explained some aspetcs of the air flow for the intake mani.

    It's kind of hard to get a proper translation, but sift through the main body and you can somewhat understand.

    (As for the intake manifold which ties the cab and the reed valve, approximately 70 degrees those which are bent are the majority, but if the manifold bends, extent and the inside of pipe loss which bend are large.

    In reason, the new model GPR and the manifold of ultra for the power priority, to straight it converted.
    Regarding the SEA DOO, the intake manifold is straight type.

    The reed valve is a top and bottom aspect, but those where it works efficiently are the reed valve of the surface.

    But, if the intake manifold which is bent is used, centrifugal force works in mass of the mixture, only the big underside of R reaches the point where it flows mainly, the reed valve of the essential surface does not work efficiently.

    In addition, although the surface does not work efficiently, kind of those which divide the top and bottom surface of the reed valve into the center section of the reed valve stuffer are marketed, but this type excessively with the above-mentioned reason, happiness, it forces and it is not the thing.

    In addition, there is the type which at the connecting hole (?) ties left and right with the manifold, but the connecting hole has had to have produced in order with the form where the center is raised, for the mixture not to accumulate inside the connecting hole.

    As for the connecting hole of straight type, at the time of engine work, the mixture accumulates in the center section, rather makes setting difficult.

    In the intake manifold, from over ten years ago as for us in side draft type, in addition, the intake chamber which evolved the connecting hole is equipped.

    With 2 wheels or, the racing machine where the intake manifold is bent it does not exist with 4 wheels (in motor sport.

    Is personal, but that Cub is associateen to the degree which looks at the intake manifold which bends.)

    In addition, inside the intake manifold whether the ぴ or the ぴ there is a tuning shop which is polished, but in excessively inhalation efficiency two cycle engines it does not improve.

    If it makes the ピカピカ, state of roughing is easy to generate the tumblers style, to the efficiency improvement of the reed valve of the surface is connected.
    If (there is no dimple of the surface of golf ball, golf ball does not fly at all.

    As for this with aerodynamic terminology, you call it airflow
    You, you looking at your own intake manifold once more, one please do to think.)

    <me>I think he is saying a straight manifold works much better as well as a roughened intake mani surface. The inlet tubes are the balance tubes on a OEM manifold..I guess.


  2. #2
    just GOT TO DO IT! great lakes gpr 1200's Avatar
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    I think too.. I think your right on the straight manifold. also his thoughts on a golf ball: When I put my stuffers in my gpr, the where from pro-tec. I noticed the part of the casting was very ruff and porous on the side that faces the fuel. Does this cause turbulance that helps mix the fuel? Would that be better than striaght fast shot? If you look at some of the other stuffers they all cause turbulance..
    But If I under stand the ideas of spacer plates for reeds: are they to reduce turbulant air flow for Reed life? or Does it let the fuel mixure atomize better?

  3. #3
    MR. SCOVILLE UNIT SUCKMYWAKE's Avatar
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    i think it attracts droplets of fuel thereby aiding in the fuel mixture

  4. #4
    ....back from the dead.... J-ME's Avatar
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    Quote Originally Posted by SUCKMYWAKE
    i think it attracts droplets of fuel thereby aiding in the fuel mixture
    What are you talking about? How does it attract?

    The above is a confusing read. Everyone should already know a rough, hewn surface is necessary in intake manifolds in non port fuel applications. (eg thottlebody FI or carbs)

  5. #5
    Connecticut CrazyA's Avatar
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    That's what I've always read and been told as well. Never smooth out the intake side of things too much. (like a mirror) The semi-rough surface aids in atomization... so I've been told.

  6. #6
    PW, I struggle to understand the post, but are you suggesting that this person is suggesting that a sidedraft manifold produces more power and efficient use of the reeds than upright? If so does your translation lead you to change your opinion of the old 65u sidedraft manifolds from a performance standpoint? Tuning still difficult no doubt.

  7. #7
    Connecticut CrazyA's Avatar
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    One thing he is saying.... ummmm, I'm pretty sure I think, is that a straight shot manifold will use all of the given reed petal surface whereas a curved or radiused manifold will want to use the bottom side mostly causing inefficiency. Sort of like in heating and AC systems using ductwork... when making a 90* turn, it's a good idea to use turning vanes.

  8. #8
    Hydrotoys's Avatar
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    If your LIMITING factor is your intake tract then it matters.... if not, then it's all just fun theory.

  9. #9
    Pistonwash's Avatar
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    I think CrazyA hit it...you'll use more reed surface with a straight mani..I've never had luck with them on a 65u, it made the jetting quirky. I guess they are also saying it is more effecient to have a roughened straight intake than a smooth bent one.

    Maybe TJ can chime in here on what manifold does what?

  10. #10

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    I`ll check this weekend and see if I can post some results from some 65u dyno runs of the two manifolds,but for sure the side drafts made more bottom & mid over the downdrafts,see what real deal numbers I can find to post,TJ

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