Dual Exhaust

[heylookitsjames]

It seems to me that due to laminar flow, two smaller pipes with the same cross sectional area as one larger pipe would infact have higher gas velocity (this can be seen when solving the Reynold's Number equation for mean velocity and using an Re of 2300 it can be seen that L, or "characteristic Length"... in this case, the diatmeter of the pipe, will result in an smaller laminar flow value). Also, if they were fused/jointed correctly, they could be as uinrestrictive as well. In addition, scavenging effect (effectively having a wave of low pressure interlope its way back into the combustion chamber that aides the successive induction charge) is more pronounced on smaller diameter pipes...

/This being said, I think that twin exhaust would look kinda dirty...