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06-27-2014, 12:22 PM #76Screaming And Flying!
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Yes 2 stroke exhaust is all about stuffing it back in as the port timing is symmetrical hence you dont have the control you need, so mix lost out the exhaust at non optimal rpms.
Dfi fixed the fuel part but not the air part
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06-27-2014, 07:18 PM #775000 RPM
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Don't confuse single cylinder port timing with expansion chamber design - two different animals.
On V outboards, the firing order helps with the fuel charge was the point.
pointer
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06-28-2014, 01:53 AM #78Screaming And Flying!
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With 120 degree timing between cylinders in the same manifold and megaphone the reverse pulse from one cylinder charges the next one.
3 and v6 engines use this effect.
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06-28-2014, 06:44 AM #79"12" Super Lite Tunnel (11') "88" 25 Yammy twin carb "BANANA SPLIT"
"77" Hydrostream Viper "87" 140 Rude heavy modded w/15" mid, Bobs nose and lwp "DANGER ZONE"
"72" Checkmate MX-13 "80" 75 Rude w/15"mid and Nitro Lu (to be restored)
"Too much is never enough" Keith Richards " Dreams become reality via hard work and perseverance" G.A.Carbonneau
"This coming from an old man that strapped two bananas together, hung a motor on it and calls it a boat" XstreamVking
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06-28-2014, 08:09 AM #80Screaming And Flying!
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06-28-2014, 12:12 PM #81Screaming And Flying!
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[QUOTEis a omc patent on this exolboatman;2653590]Do v4s dits the same but at 180 degrees? Gary[/QUOTE]
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
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06-28-2014, 12:20 PM #82
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06-28-2014, 12:23 PM #83
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06-28-2014, 12:38 PM #84Screaming And Flying!
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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
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06-28-2014, 12:52 PM #85
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
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06-28-2014, 01:34 PM #86Screaming And Flying!
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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.
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06-28-2014, 02:02 PM #87Screaming And Flying!
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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?
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06-28-2014, 02:15 PM #88Screaming And Flying!
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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 crossflowLast edited by powerabout; 06-28-2014 at 02:27 PM.
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06-29-2014, 06:13 PM #89
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?
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07-01-2014, 02:47 PM #90