2 in 2 exhaust wrong?

[incredible]

Im thinking about making an exhaust of my own to the streetfighter cause i dont really like any of the ones there is. So i was thinking ofmaking one with 2 individual pipes each going from there own cylinder and out. Is this for some reason not good for performance? I dont see it on any other motorcycles these days exept cruisers. The more usual thing is 2-1-2 or 2-1-1. For some reason the 2 individual pipes always merge somewhere along the way, why is that?

[Jonny DeWog]

Most twins have a 2-1-2 setup as it allows a "balance-pipe" to effect the gasflow between the two cylinders. In its simplest form, a certain degree of 'blow-back' (a pulsed pressure wave from each time the exhaust opens) sends a pressure wave to the opposing cylinder, reducing the amount of unburnt fuel escaping form the preceding stroke, hence greater efficiency etc etc.

Truth is, exhaust design is more a dark art than everyday science. There are so many influences in an 'efficient' exhaust; length of pipe(s), placement of the 'collector' (eg 4-2, 4-2-1, 2-1-2, etc), pipe diameter, tuning across a rev-range (what works at low revs doesn't at high-revs, and vice-versa) and on and on.

(....then the engineers demand that they're made of the lowest weight that's practicable, and how to place exhaust flaps and catalytic converters to get them road legal, whilst the designer try their best with all these constraints to make the plumbing either hidden away, or to at least look stylish....)



jdw

[PluckedDuc]

Originally Posted by Jonny DeWog

Most twins have a 2-1-2 setup as it allows a "balance-pipe" to effect the gasflow between the two cylinders. In its simplest form, a certain degree of 'blow-back' (a pulsed pressure wave from each time the exhaust opens) sends a pressure wave to the opposing cylinder, reducing the amount of unburnt fuel escaping form the preceding stroke, hence greater efficiency etc etc.

Truth is, exhaust design is more a dark art than everyday science. There are so many influences in an 'efficient' exhaust; length of pipe(s), placement of the 'collector' (eg 4-2, 4-2-1, 2-1-2, etc), pipe diameter, tuning across a rev-range (what works at low revs doesn't at high-revs, and vice-versa) and on and on.

(....then the engineers demand that they're made of the lowest weight that's practicable, and how to place exhaust flaps and catalytic converters to get them road legal, whilst the designer try their best with all these constraints to make the plumbing either hidden away, or to at least look stylish....)



jdw

Good post mate.