ferp420 Posted December 4, 2012 Share Posted December 4, 2012 I was just wondering if anybody's ever tried using a expansion chamber on the exhaust side as a performance upgrade I know they use them on 2 strokes bikes but I'm also starting to see them on the hi end 4 stroke race bikes our motors being so close to a motorcycle just wondering if it would give us any more punch any exhaust gurus out there with some insight ? Quote Link to comment Share on other sites More sharing options...
Hatchback Lou Posted December 5, 2012 Share Posted December 5, 2012 bump. I'd like to know as well! Quote Link to comment Share on other sites More sharing options...
zukiru Posted December 5, 2012 Share Posted December 5, 2012 expansion chambers on 4 stroke bikes are done to enhance the sound . They don't work for adding horsepower to a 4 stroke engine as far as I know. Quote Link to comment Share on other sites More sharing options...
Hatchback Lou Posted December 5, 2012 Share Posted December 5, 2012 Thanks! Thats kind of what I was thinking, but i don't know much about exhausts or bikes. Or bike exhausts. Quote Link to comment Share on other sites More sharing options...
86 Wonder Wedge Posted December 5, 2012 Share Posted December 5, 2012 Well, expansion chambers are really meant to "backfeed" a pressure wave back to the combustion chamber to create a sort of valve to keep the new stuff from exiting the exhaust side, essentially turning it into a 4 stroke. On 4 strokes (systems with valves, lol) bouncing back the pressure wave/stalling the gases exiting doesn't help when there is a valve in a way... lol Quote Link to comment Share on other sites More sharing options...
ferp420 Posted December 5, 2012 Author Share Posted December 5, 2012 heres a link to fmf racings powerbomb pipe http://www.fmfracing.com/Products/MX/44 what would %10 do for out little motors i know it would cost a fortune to make one for our cars fmf has been making pipes for along time and can spend the money and time on r&d doing that for a little old subaru would fall under the catagory of wtf dude why it sure would be nice though Quote Link to comment Share on other sites More sharing options...
cubastreet Posted December 5, 2012 Share Posted December 5, 2012 an expansion chamber first returns a negative pressure wave that helps draw out exhaust gases and also helps pull up the fresh charge from the crankcase. Some of the fresh charge is often also sucked out the exhaust port It then returns a positive pressure wave that stuffs the charce back onto the cylinder just before the port closes, giving a supercharging effect. The pressure waves travel at the speed of sound, so this supercharging effect normally happens over a fairly narrow rev range, giving the famous 2 stroke powerband. It doesn't turn it into a 4 stroke, the engine still fires once every revolution. You could probably set up a single baffle cone to aid in extraction of exhaust gases but you'd really need one per cylinder which isn't really feasible with siamese exhausts. Quote Link to comment Share on other sites More sharing options...
coxy Posted December 20, 2012 Share Posted December 20, 2012 FMF Powerbomb pipes are a real mongrel to jet on the dyno compared to a normal pipe so I wouldn't want one on a car engine. Quote Link to comment Share on other sites More sharing options...
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