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  1. #91
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    Quote Originally Posted by powerabout View Post
    [QUOTEis a omc patent on this exolboatman;2653590]Do v4s dits the same but at 180 degrees? Gary
    They dump to common megaphone so its 90 degree pulses.
    There is an omc patent explaining it from the 60's on the web somwhere
    You are going to have to explain all this to me ... I have no idea where 90 pulses will come from with cylinders firing 180 apart.

  2. #92
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    [QUOTEis onlyMark75H;2653653]You are going to have to explain all this to me ... I have no idea where 90 pulses will come from with cylinders firing 180 apart.[/QUOTE]
    4 x 90 = 360
    There is only one passage in the megaphone on v4 and 2 on a v6

  3. #93
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    Then it has nothing to do with 180 degrees other than co-incidence

    You still need to explain some benefit. At 90 I think the transfer ports are generally still open and this would be a problem rather than benefit. Add to that, the fact that its about 30 before the exhaust port closes, a lot of time prior to the critical event.

    Try to dig up that patent you referenced

  4. #94
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    Quote Originally Posted by Mark75H View Post
    Then it has nothing to do with 180 degrees other than co-incidence

    You still need to explain some benefit. At 90 I think the transfer ports are generally still open and this would be a problem rather than benefit. Add to that, the fact that its about 30 before the exhaust port closes, a lot of time prior to the critical event.

    Try to dig up that patent you referenced
    What can I say thats how all OMC v4's are made. They could have very easily had it as 2 separate 2 cylinder engines but they clearly wanted all 4 cylinders to dump to one megaphone.
    I was just stating the obvious that it fires each 90 hence the pulse comes back at each 90 degrees.

    I'll find the patent.
    Last edited by powerabout; 06-28-2014 at 02:00 PM.

  5. #95
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    http://www.google.ca/patents/US3692006
    I did think there was one from the 60's?
    drawings are of the race motor but basically morphed into the 135 style.

    Just thinking, is the exhaust design to suit the dump or the pulse coming back?

  6. #96
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    3520270 TUNED EXHAUST GAS SYSTEM FOR OUTBOARD MOTOR July 1970 Miller
    3507301 COLLECTOR AND METHOD OF MAKING THE SAME April 1970 Larson
    3470690 EXHAUST HEADER October 1969 Thompson
    3385052 Exhaust system May 1968 Holterman et al.
    3233598 Marine engine February 1966 Van Ranst
    3045423 Muffled exhaust release for an outboard motor July 1962 Hulsebus
    2921567 Slot-controlled two-stroke cycle internal combustion engine January 1960 Medenus
    2858667 Water cooled exhaust manifold November 1958 Reske

    there we go, keep us all busy for hours...
    Now I just need to the find the Rick McChesney one on the etec crossflow
    Last edited by powerabout; 06-28-2014 at 02:27 PM.

  7. #97
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    How does compression and flow rate differ from a 5 peddle intake to a larger 7 peddle system? Wouldnt the flow speed be slower going in?

  8. #98
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    http://www.torqsoft.net/reed-petal-design.html
    Here is a nice tool for calculating reed HZ to RPM.

  9. #99
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    Quote Originally Posted by powerabout View Post
    http://www.google.ca/patents/US3692006
    I did think there was one from the 60's?
    drawings are of the race motor but basically morphed into the 135 style.

    Just thinking, is the exhaust design to suit the dump or the pulse coming back?
    I'm lost already doesn't the first line say 3 cylinders or multiples?

  10. #100
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    Quote Originally Posted by Mark75H View Post
    I'm lost already doesn't the first line say 3 cylinders or multiples?
    yes 3 or more
    further down it talks about V4 and all the drawings are a V4

  11. #101
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    I found it interesting that a prior patent had described the ability to sonic-supercharge a two cylinder by a tuned common exhaust. OMC just expanded it to include "three or more cylinders". The other referenced patents were very interesting also. I also realized how hard it is to read a patent...


    Thanks for the links.


    98 Laveycraft Sebring 20.2 Tunnel 280 "catchin" motor. 90s? It's enough for me!

  12. #102
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    Quote Originally Posted by dwilfong View Post
    I can see all the ex chest work that is talked about. So making the chest larger (removing the stuffing) will let more charge load up in the chest. Then a shorter wider angle tuner will pull more at top RPMS to load the large chest.
    So how much stuffing you remove will determine the tuner used.
    More stuffing removed less low end power.
    So removing too much stuffing on a stock timed eng with a stock tuner my not show a increase in power but less power?
    So if you open the chest up and run a shorter/wider angle tuner then you lose bottom end but gain on higher RPM's
    But if you put a 1" spacer in front of the reeds, would it help recover some of the lost the bottom end???

  13. #103
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    One thing to consider when stuffing the crank case you are increasing velocity through the ports. when the velocity increases the angles and directions of the transfers need to be adjusted.

  14. #104
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    A spacer will not help with the bottom end loss by hogging the ex chest out. The spacer is more to straiten the intake tract out to the far side of the reeds than any thing.

  15. Likes Mark75H liked this post
  16. #105
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    Quote Originally Posted by dwilfong View Post
    A spacer will not help with the bottom end loss by hogging the ex chest out. The spacer is more to straiten the intake tract out to the far side of the reeds than any thing.
    Thanks for the reply, I really appreciate all of the knowledge and advice on this board!

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