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Old 02-02-2012, 08:54 PM   #18
Retired Roadracer
Joined: Jun 2007
Location: Denver 'Burbs, Colorado, USA.
Oddometer: 6,026
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.
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.
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