View Full Version : Any manufacturers ever mess with 2 strokes with exhaust valves?
CDave
10-18-2004, 09:33 PM
Kinda like a Dietroit Diesel.
merklebob
10-20-2004, 09:23 AM
last on i saw was a 35hp oliver outboard from 1959. may have been inlet valves thru. this was a very strong motor for its day but hard to find part for.
Blizz
10-26-2004, 01:03 AM
All of the snowmobile mans are using exhaust valves and have been doing so for quite awhile some of the small pro racing outboards have them also.
BarryStrawn
10-26-2004, 08:31 AM
I've never seen or heard of a production outboard with an exhaust "power valve" as is commonly used to vary the height of the exhaust port.
The Detroit Diesel two stroke uses a camshaft and poppet valves in the head. Cycling rate would be a problem on a high speed two stroke. Even a 7,000 rpm two stroke would require a valvetrain equivalent to a 14,000 rpm four stroke. $$$$
I thought the ones on sleds were for varying the amount of exhaust backpressure to suit the RPM range.
So it's actually variable port timing?
BarryStrawn
10-26-2004, 09:53 AM
Several variations. Quick search found these links.
http://www.offroadhaven.com/powervalve.htm
http://www.poetonaptec.co.uk/technica/mpcxvalv.htm
Blizz
10-27-2004, 12:30 AM
yes the ones on sleds are for varying backpressure to help it keep on or get back on the pipe faster, it also helps torque, kinda like a slider that the mod outboard guys use.
sosmerc
10-27-2004, 12:45 AM
...here's something new from STIHL
http://www.stihlusa.com/whatsnew/news_fourmix.html
Scale Performance
12-14-2004, 06:11 PM
the e-tec 70 hp 2 cyl will more then likely have a exhaust valve.
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