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Posted: Tue Jul 18, 2006 4:19 pm
by se50
Kenny_McCormic wrote:how does no backpressure mess up your engine?
iv yet to see an explanation
No pressure ends up wasting fuel, and making the engine loose power. To my understanding, in an expansion chamber, the sound waves pull fuel out of the cylinder in the first cone, and then they reflect off the last cone, and force more fuel back into the cyl.

Even on a 4 stroke, no backpressure messes up fuel economy. I had a Murray pushmower that would run about an hour on a tank (about a quart) of gas (and half a quart of oil :D) on the stock muffler. I made a new pipe for it from some 1/2" NPT galvanized fittings, and by the time I was done, I could mow about 1/2 hour on a tank of gas, and it would stall in the grass often. Before, I could mow down small trees without much of a problem with that mower.

Plus, a really loud pipe does get kind of annoying, if it doesn't sound cool. Last winter, my Kawi 185 four wheeler had a bad exhuast leak at the header. It sounded terrible, and not like performance exhaust at all, and to go drive out on the lake (frozen), I'd wear ear protection, so my ears weren't ringing after driving it. :D

Posted: Tue Jul 18, 2006 7:06 pm
by noiseguy
se50 wrote:I'm working on a custom expansion chamber exhuast for my Elite now. I'm doing calculations, and learned the hard way (at least on scrap) that no matter how low of current and how small of rods you use, you just can't weld the metal thin enough for an expansion chamber with a stick welder. :D I'm looking at buying a used Miller MIG welder soon, which should be able to weld as thin as 24 ga sheet metal. :D If the sheet metal is cheap enough, I'm going to mess around with a few custom pipes, and fine out which design works best, and get a set of dimensions for making one for an Elite that people can have.
I've been working on that too. Go read this:

http://www.hondaspree.net/phpBB/viewtop ... 3&start=75

There's also a link in Adv Tech Docs for a pipe calculator.