Multicylinder 2 stroke into one expansion chamber?

Discussion in '2 smokers' started by Chillis, Jan 22, 2012.

  1. Chillis

    Chillis Long timer

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

    Just curious.
    #1
  2. Tosh Togo

    Tosh Togo Long timer

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    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.
    #2
  3. PistonPants

    PistonPants Crankcase Scavenger

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    Snowmobiles do it all the time.

    Piston
    #3
  4. JonnyCash

    JonnyCash turd polisher

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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.
    #4
  5. trophymoto

    trophymoto MACDADDY!

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  6. anotherguy

    anotherguy unsympathetic

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    An associate will build these for RZ350 Yamahas.


    [​IMG]
    #6
  7. dtysdalx2

    dtysdalx2 PITA but useful

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    Yep, my old Yamaha Phazer does.

    That pipe above is quite a piece of work! :eek1
    #7
  8. Chillis

    Chillis Long timer

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    I didn't think to look at the snowmobile market.

    That pipe above looks great!
    #8
  9. Shocktower

    Shocktower Long timer

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    Rediculous how on earth will your GF burn both calfs with out twin pipes :lol3

    BTW that 2-1 is sexy looking
    #9
  10. anotherguy

    anotherguy unsympathetic

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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.

    [​IMG]
    #10
  11. tkent02

    tkent02 Long timer

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    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..
    #11
  12. scrambler73

    scrambler73 Been here awhile

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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.
    #12
  13. gplracing

    gplracing Adventurer

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    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
    #13
  14. anotherguy

    anotherguy unsympathetic

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    Welcome to the Jungle Glyn. :D
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  15. scrambler73

    scrambler73 Been here awhile

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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.


    #15
  16. motu

    motu Loose Pre Unit

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    I had a GT750 with a 3 into 1 too - three header pipes jammed into a 3in tube with a muffler stuck on the end. The GT750 wasn't about top end anyway, it was a grunt machine. Certainly a cheaper option than the 4 huge mufflers it had stock.
    #16
  17. gplracing

    gplracing Adventurer

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    The pipe that was tested flollowed the 2-2 set up with in 2hp, + at times and - in places. The test wasn't done very well to be honest. It was just bolted on with out any fueling or ignition changes and run.

    The pipe in the pic is a different design and designed in the sim differently than the pipe tested. IMO the other pipe was designed with an unrealistic wall temp. Time will tell lol.

    Glyn
    #17
  18. Duck_Pilot

    Duck_Pilot Retired Roadracer

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    BINGO!! If you want the best out of a 2T engine, you need separate chambers. Next best would be a single-chambered 'twingle', where the pistons are in sync with each other..... there may be a pressure loss, but at least the sonics won't fight each other.

    The shape of a 2T expansion chamber works kiss-'n-cousins to a supercharger, with no mechanical moving parts. The placement and shape of the forward cone generates vaccuum to help drag out the old, spent charge - and help pull the fresh charge up from the cases while the transfer and exhaust ports are all open (scavenging). Then the rear cone reverses that wave, to force-feed a portion of fresh fuel charge - that had been pulled into the headpipe - back on top of the piston, before the exhaust port closes. The powerband of a 2T engine is greatly influenced by the placement and shape of both cones.

    If you need light weight and cornering clearance more than power, then the 3-1 chamber may be fine for you. I faced several Kawi 750's and GT-750's with those pipes on local racetracks, and my under-carbureted GT-550 outran 'em all easily. 200CC's lighter displacement, and still no contest.
    #18
  19. Deuce

    Deuce Crazy Canuck

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    This was my first street bike. I was 18 at the time ('76). Has a custom made 2 into 1. Bike ran great especially on the 'pipe'. I had to repack that thing every 2 weeks if I wanted to be semi-quiet with it. :1drink Did a lot of miles with that bike travelling between Kingston, Ontario and Montreal on the weekends.

    [​IMG]
    #19
  20. bringenufgun

    bringenufgun Been here awhile

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    had a 72 h2 kawasaki back in the mid to late 70's. when i bought the bike it came with a three into one expansion chamber. bought a new set of chrome plated dencos for it($279.00 in 1977) and they made a world of difference on the 750. the three into one was binned shortly after.
    #20