Quote:
Originally Posted by Vulpe
I'm really intrigued as to how this sound is the result of the exhaust layout.
I immediately thought of the WRX/STI but those sound completely different. So I was thinking it was because the unequal part happens before the turbo and not after. But the FRS/BRZ has a similar sound with no turbo. Is the unequal portion changing between the headers and exhaust that much of a difference?
|
It doesn't really matter where the unequal part happens, it is the total length from exhaust port to exhaust tip.
Exhaust pulses travel at the speed of sound (roughly) so for them to emerge from the exhaust pipe where we hear them in equal spacing and in Inline 6 firing order (1 pulse every 120degrees of crank rotation) the pipe lengths must be pretty much the same for all cylinders.
But S55 design has both turbos rear facing, so the 456 (rear) turbo exhaust exit is a good foot further rearward than the 123 (front) turbo exit and no attempt is made to cater for this in the exhaust system.
So the pulses from 456 will clash with 123 pulses further back and will not give equally spaced "smooth" 120deg separated 153624 pulses.
The N54 had opposing turbos so that made the gas flow routes symmetrical as spool twice says.