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Old 01-22-2012, 11:35 PM   #1
brianwheelies OP
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Multicylinder 2 stroke into one expansion chamber?

Has this ever been done? Every performance exhaust for 2 stroke multi's has an expansion chamber for each cylinder.

Just curious.
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Old 01-23-2012, 12:00 AM   #2
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Originally Posted by brianwheelies View Post
Has this ever been done? Every performance exhaust for 2 stroke multi's has an expansion chamber for each cylinder.

Just curious.
Some early TZ700/750s used a pair of 2-into-1 chambers, but they were more an answer to the flat-sided OEM pipes than an actual tuning aid. They were ugly, but worked.

Two cylinders into a common pipe should work, as long as they're both in synch as the TZs were.
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Old 01-23-2012, 12:37 AM   #3
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Snowmobiles do it all the time.

Piston
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Old 01-23-2012, 03:33 AM   #4
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I've seen 3 into 1 pipes offered for GT750's. What I understand is that they run great, but give a strong midrange, not a top end hit.
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Old 01-23-2012, 07:02 AM   #5
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like this

http://omarsdtr.com/Ex550suz.html
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Old 01-23-2012, 07:48 AM   #6
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An associate will build these for RZ350 Yamahas.


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Old 01-23-2012, 07:58 AM   #7
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Originally Posted by PistonPants View Post
Snowmobiles do it all the time.

Piston

Yep, my old Yamaha Phazer does.

That pipe above is quite a piece of work!
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Old 01-23-2012, 09:24 AM   #8
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I didn't think to look at the snowmobile market.

That pipe above looks great!
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Old 01-23-2012, 02:10 PM   #9
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Rediculous how on earth will your GF burn both calfs with out twin pipes

BTW that 2-1 is sexy looking
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Old 01-23-2012, 03:12 PM   #10
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If anyone is interested I've asked Glyn (the guy who built the 2:1 pipe) for permission to put some contact information up here. Here's a set of pipes he makes for +4MM stroked RZ350's-$550 CAD. He does all sorts of engine work for road going 2 strokes.

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Old 01-23-2012, 03:53 PM   #11
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Originally Posted by JonnyCash View Post
I've seen 3 into 1 pipes offered for GT750's. What I understand is that they run great, but give a strong midrange, not a top end hit.
I rode one, 25 or so years go. Good mid range, good top end, much faster than a stock GT 750. Probably not as good on top as three separate pipes would have been, but I never rode one like that, so I don't really know..
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Old 01-23-2012, 08:40 PM   #12
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2 strokes will always make the most horsepower with ONE individual expansion chamber per cylinder.
As soon as you add 1 or 2 more cylinders to the mix, the soundwaves (for lack of a better explaination) begin to collide in a way that disrupts the whole purpose of an expansion chamber.... Cramming unburnt mixture back into the cylinder before the port closes.

There is a guy working on a 3 into 1 for a Kawasaki Triple that will have interchangeable "chambers".. all made to work at different RPM's. It will be pretty cool to see how it all turns out.
Ive had a few different old-school brands of 3 into 1's on H1's and H2's and they all work the same... Good low end and midrange grunt......but at 6 grand or so, absolutely shut off like you are hitting the kill switch. 6 grand on a triple is where the fun is supposed to start, not stop.

Ive also ridden a buffalo with one of Omar's 3 into 1's and it ran well. Buffalo's were never high revving, so you didn't really miss that last 1000 revs.
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Old 01-24-2012, 09:51 AM   #13
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Originally Posted by scrambler73 View Post
2 strokes will always make the most horsepower with ONE individual expansion chamber per cylinder.
As soon as you add 1 or 2 more cylinders to the mix, the soundwaves (for lack of a better explaination) begin to collide in a way that disrupts the whole purpose of an expansion chamber.... Cramming unburnt mixture back into the cylinder before the port closes.

There is a guy working on a 3 into 1 for a Kawasaki Triple that will have interchangeable "chambers".. all made to work at different RPM's. It will be pretty cool to see how it all turns out.
Ive had a few different old-school brands of 3 into 1's on H1's and H2's and they all work the same... Good low end and midrange grunt......but at 6 grand or so, absolutely shut off like you are hitting the kill switch. 6 grand on a triple is where the fun is supposed to start, not stop.

Ive also ridden a buffalo with one of Omar's 3 into 1's and it ran well. Buffalo's were never high revving, so you didn't really miss that last 1000 revs.
Hi guy's I'm Glyn the guy that built the 2-1.

This is still in the very early stages of development, but has shown some goos results.

With the post quoted your are right to a point about the pulses getting confused. But the way the crank is phased plays a huge role in the end result.
As this is going onto a parallel twin that is phased at 180* this is in my favour. The first one was dyno'd last week in Germany, a different design to the one shown here but the same principle.
It did quite well for it's first run only 4hp down on the 2-2 set up he was running and it peaked at 9400k against his 9700k with the 2-2.
I will agree that a 3-1 is asking for trouble and will never be able to give you any top end power to speak of, but the 2-1 with a 180* can be made to work really quite well.
How fare I'll take this I don't know as I am time limited at the mo, but I know that it will be as good as any after market off the shelf pipe currently out there.

Glyn
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Old 01-24-2012, 11:36 AM   #14
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Welcome to the Jungle Glyn.
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Old 01-24-2012, 06:12 PM   #15
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Cool Glyn...and I do agree that with 180 phasing, if the 2 into 1 is designed well enough (and it sounds like you are definately on the right track!), you will not have nearly the "problems" with soundwave turbulence that one would have with a 3 cylinder.

How was low end grunt compared to the 2 into 2? Thats actually quite impressive that it was only 4hp and 300 revs down on peak.


Quote:
Originally Posted by gplracing View Post
Hi guy's I'm Glyn the guy that built the 2-1.

This is still in the very early stages of development, but has shown some goos results.

With the post quoted your are right to a point about the pulses getting confused. But the way the crank is phased plays a huge role in the end result.
As this is going onto a parallel twin that is phased at 180* this is in my favour. The first one was dyno'd last week in Germany, a different design to the one shown here but the same principle.
It did quite well for it's first run only 4hp down on the 2-2 set up he was running and it peaked at 9400k against his 9700k with the 2-2.
I will agree that a 3-1 is asking for trouble and will never be able to give you any top end power to speak of, but the 2-1 with a 180* can be made to work really quite well.
How fare I'll take this I don't know as I am time limited at the mo, but I know that it will be as good as any after market off the shelf pipe currently out there.

Glyn
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