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Thread: Outboard ????????

  1. #1
    Im just curious if any of the boat motor companys have ever used exhaust valves on two strokes. They started on snowmobiles a few years ago. They work great.
    As the throttle opens the gate valve opens. What this does is change port timing. It gives you a huge torque curve just off idle.
    I just wondered.....Dan

  2. #2
    how ya feeling? actualy they do not change the port timming at all they just change the amount of backpreasure and reverse pulse. the exhaust port is open at the same time. but they do make a big diff. throughout the rpm range.

  3. #3
    So they change the pipe volume? How does that work? Im sure with 2 strokes on the way out the R&D is probaly not up to snuff.
    Im feeling pretty good.

  4. #4
    dan, when the exhaust is forced out there is still some unburned fuel in it. The shape of the pipe, how far from the cyl. the pipe bends, the shape all play into how much of that unburned fuel is sucked back into the cyl. adding more hp. It used to be that you had to give up some low end to gain top or mid range, but with the valves now being used it allows for the best of all. it gives more back pres. at low rpm. forcing more unburned fuel back into the cyl. and at high rpm it opens because there is much more exhaust and it would choke the motor out if it tried to force it all back into the cyl. it is actualy much more complicated, but i tried to make it easy. Good to here you are feeling better.

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