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Thread: 70cc twin exhaust

  1. #111
    Senior Member -Rick-'s Avatar
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    Re: 70cc twin exhaust

    Quote Originally Posted by tbrum View Post
    The exhaust from both cylinders enters any single can or pipe at the same time regardless of configuration since it is an opposed twin.

    Trevor, This is from Dave at DA. This is the reason I made the headers to match in length.

    Hi Rick
    Sorry for the late reply. We haven’t had a chance to really try them. KS makes good stuff, but getting good performance with a 2 into 1 system is very difficult. The 2 exhaust pressure charges fight each other as they come together in the can or header. The only time we have seen it work is with the DA70/ "Y" header MTW TD110H combo. So far, no other canister set up comes close. Again, we can't comment too much about the KS 2 into 1 canister until we get some testing in.
    Another thing to consider is the spacing between the standard headers would be too wide to match up to the two inlets on the muffler. KS might offer special headers to match up, but if they do, I haven't seen them yet. We only stock the versions for 2 canister systems.
    If you give one a try, I would recommend something rated for at least 80cc or larger. The DA70 exhaust outlets are 22 mm dia so the inlets to the canister and the headers should be 22mm.
    Let us know if you have more questions.
    Thanks
    Dave

  2. #112
    Senior Member -Rick-'s Avatar
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    Re: 70cc twin exhaust

    Quote Originally Posted by rpm View Post
    Are you meaning that the 2 into 1 headers don't account for the cylinder offset thereby unequalizing the exhaust entering the canister? And it has been found to be a problem?
    From what I have been told, yes.

  3. #113
    Senior Member tbrum's Avatar
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    Re: 70cc twin exhaust

    What Dave is getting at is that because the exhaust comes out of each cylinder at the same time the exhaust from each side can fight each other (competing pressures) whether in header or canister. What he’s implying here is that a single can setup is not as good as a twin can setup where the sides do not come together in any way. And he’s only had luck with the MTW single if you go single.
    Last edited by tbrum; 02-25-2019 at 09:38 PM.

  4. #114
    Senior Member -Rick-'s Avatar
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    Re: 70cc twin exhaust

    Yes Trevor, which is why I made the headers different lengths and that they hold the same volume of air before the can. My exhaust discharge are both entering the can at the same time. Not apart from each other. Not fighting each other. The discharge is entering the can as one, same as a single cyl.
    Last edited by -Rick-; 02-25-2019 at 11:47 PM.

  5. #115
    Senior Member -Rick-'s Avatar
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    Re: 70cc twin exhaust

    Quote Originally Posted by tbrum View Post
    What Dave is getting at is that because the exhaust comes out of each cylinder at the same time the exhaust from each side can fight each other (competing pressures) whether in header or canister. What he’s implying here is that a single can setup is not as good as a twin can setup where the sides do not come together in any way. And he’s only had luck with the MTW single if you go single.
    Are we having fun yet?!

    What you have been trying to say Trev is that it is a moot point at the timing of the discharge. The problem is that here is two discharges entering the same can and fighting each other?

  6. #116
    Senior Member wingburner's Avatar
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    Re: 70cc twin exhaust

    Rick, any update on the exhaust?

  7. #117
    Senior Member -Rick-'s Avatar
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    Re: 70cc twin exhaust

    Quote Originally Posted by wingburner View Post
    Rick, any update on the exhaust?
    Have not run it anymore. Waiting for it to warm up outside a bit. Should have a plane for it by the the end of the month. But still plan on running it on the stand for a bit more.

  8. #118
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    Re: 70cc twin exhaust

    Didn't get it off the ground. Wheel fell off Very quiet.

    https://youtu.be/C3BRzFtsvUI

  9. #119
    Senior Member rpm's Avatar
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    Re: 70cc twin exhaust

    Too bad about the wheel. It seems to sound good though. Hope your next time goes better.
    Humber Valley RC Flyers

  10. #120
    Senior Member -Rick-'s Avatar
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    Re: 70cc twin exhaust

    Quote Originally Posted by rpm View Post
    Too bad about the wheel. It seems to sound good though. Hope your next time goes better.
    Two flights on it yesterday. She fly's well.

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