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Old 01-25-2012, 01:31 AM   #16
Loose Pre Unit
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Joined: Dec 2001
Location: New Zealand
Oddometer: 4,619
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.
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Old 01-25-2012, 05:52 AM   #17
Joined: Jan 2012
Location: Nova Scotia Canada
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Originally Posted by scrambler73 View Post
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.
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.

GPL Racing
Nova Scotia
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Old 02-02-2012, 08:54 PM   #18
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Joined: Jun 2007
Location: Denver 'Burbs, Colorado, USA.
Oddometer: 6,149
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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Old 02-03-2012, 11:59 AM   #19
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Joined: Nov 2001
Location: Vancouver Island, Bitchin' Columbia, Canada
Oddometer: 2,856
'72 T500 production racer

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. Did a lot of miles with that bike travelling between Kingston, Ontario and Montreal on the weekends.

"Experience alone is not the great teacher; Experience has to be multiplied by intelligence to yield sustained progress." Phil Schilling
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Old 02-07-2012, 05:21 PM   #20
vernon dent
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Joined: Oct 2010
Location: apparently halfway to motorcycle hell
Oddometer: 713
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.
I only ride 'em. I don't know what makes 'em work.

vernon dent screwed with this post 02-17-2012 at 06:59 PM
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Old 02-13-2012, 02:36 AM   #21
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Joined: Sep 2007
Location: In the TARDIS
Oddometer: 3,075
My Rotax 582 ultralight engine uses a 2 into one pipe. It's 65 hp, rotary valve, very wide power band. I think the 100 hp snowmobile and watercraft versions use 2 into one also.
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