got a questions about exhaust system
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why 2 stroke bikes have exhaust pipes with stomaches and 4 stroke without ?
why 2 stroke bikes with 4 cylinders must have 4 exhaust pipes yet 4 stroke bikes with 4 cylinders can have four pipes diverted into one muffler -
i think it is cos the stomache of the 2 strk pipe is the catalystic converter. for 4 strk bikes it is located inside the muffler itself.Originally posted by Mama:why 2 stroke bikes have exhaust pipes with stomaches and 4 stroke without ?
why 2 stroke bikes with 4 cylinders must have 4 exhaust pipes yet 4 stroke bikes with 4 cylinders can have four pipes diverted into one muffler -
the number of muffler for a two stroke is depend on the number of cylinder it have .
example... PGM4 V2 2 cylinder - two pipes, Rossi NSR500 V4 4 cylinder - four pipes, NSR150sp 1 cylinder - one pipe
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Speed is Nothing without Control -
*beep* sorry it's not like that... a 2 stroke engine has no dedicated exhaust valve (before you scream "POWER VALVE!!!", read first) like a 4 stroke engine to close off the exhaust port when the cylinder is compressing the air-fuel mixture. a 2 stroke engine charges its cylinder via back pressure from the pipe. this is a combination of factors like length of exhaust pipe, rpm, shape of the belly. so for each engine, the design of the belly is very important. exhaust pipe manufacturers spend quite a sum just on R&D for the right shape of the belly.Originally posted by fp2075r:i think it is cos the stomache of the 2 strk pipe is the catalystic converter. for 4 strk bikes it is located inside the muffler itself.
would really advise everyone to run a search for 2 stroke engines, and understand how they work.. then won't kenna chopped by motordiams who tell you that they do "one small mod" and your bike will "fly" and all that nonsense. it might be true, but the engine works as a system, no one SINGLE mod will maximize the full power of your engine...
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rock hard... ride free... -
so whats the purpose of the belly ? is it to store exhausted air then allowed it to go back to charge the cylinder ?
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How come I feel like I'm sitting in my lect hall again....
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not really.. it's something about fluid (exhaust in this case) that i don't fully understand myself either, should have paid more attn during physics lecture during my JC days.. hahaha.. the thing is, having an optimally shaped (exhaust companies like arrow spend big money on R&D just to get the right shape) belly allows the "exhaust wave" to charge up the cylinder.Originally posted by Mama:so whats the purpose of the belly ? is it to store exhausted air then allowed it to go back to charge the cylinder ?
in a sense, the exhaust gases do not re-enter the cylinder via the exhaust port, but rather, it forms a "wall" that fresh air/fuel collides with right at the exhaust port, hence most of it stays inside. but most of the time, a little air/fuel leaks out before the port is closed by the movement of the piston, this is called "scavenging". which is why 2 stroke motorcycles are banned in some countries, and are always the target of environmentalists.
but this is the beauty of the design of a 2 stroke engine. simplicity in design, no cumbersome and heavy cam chains, valves, lifter arms etc.. high power-to-weight ratio. the scavenging property is something that the most intelligent and creative engineers cannot fix... so it's natural lah.. but honda has come up with a 2 stroke engine called EXP-2, that uses pre-detonation to achieve complete combustion, coupled with their "post-cylinder" combustion thingy, it's a promising 2 stroke engine that environmentalists won't kaopeh about. tested and proven on an enduro scrambler, won a race.. but dunno what happened to the design.. they're not using it leh...
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rock hard... ride free... -
so to say the belly is use to store up exhausted air so that it wil form a wall to prevent the fresh air/fuel from escaping ???
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yup.. something like that. the buffering part won't be possible without a stomach...Originally posted by Mama:so to say the belly is use to store up exhausted air so that it wil form a wall to prevent the fresh air/fuel from escaping ???
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rock hard... ride free... -
what is this term buffering means ?
is it to say if without belly the the fresh air/fuel will escape thru the exhaust port in the cylinder ? -
ah, yeah... it will not escape completely, just that compression of the air/fuel mix would not be that much if the belly is not there. in a 4-stroke, what happens during the compression stroke is that both intake and exhaust valves are closed when the piston is moving up. hence, provided the piston rings are working, the mixture above is compressed, before the spark plug fires. in a 2 stroke, there's no such mechanism. there will be a point of time where both intake and exhaust PORTS are not blocked by the piston. so as the fuel comes in from the intake, as the piston moves up, the exhaust must be there to "block" the mixture, so that compression can occur at that moment, before the piston moves past the exhaust port, hence sealing it.Originally posted by Mama:what is this term buffering means ?
is it to say if without belly the the fresh air/fuel will escape thru the exhaust port in the cylinder ?
wah kaoz.. damn hard to type sial.. must look at the diagram to describe what's happening. go to www.howstuffworks.com and see leh!
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rock hard... ride free... -
when my friend was explaining how 2-stroke carbs work, even got diagram.. power sial!Originally posted by operator:How come I feel like I'm sitting in my lect hall again....
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rock hard... ride free...