carguy123 wrote:
The traditional position is after the cat and before the exhaust, but he's trying to keep exhaust extra quiet and mellow so he wants to put the mufflers after the cats and the X pipe afterwards. To me it seems that the X pipe serves the same purpose no matter where it's located in the system. Am I wrong - AGAIN?
When exhaust gasses enter a traditional chambered muffler, they (generally) see an infinite volume - going from a 2.5" pipe into a muffler that's 12" x 4" totally disrupts the gas flow. After the muffler, the exhaust pulses are completely different, totally muted from what they were before the mufflers.
An X or H pipe is designed to utilize exhaust pulses on one bank to help scavenge the other bank. Because of this, it needs to happen before the mufflers at a point designated by the engine's characteristics. Software like PipeMax lets you input your engine and cam data and it will spit out recommended placement of the X or H pipe.
A 2-into-1 muffler will not act the same as a properly-place X or H pipe.
Generally speaking, larger diameter exhaust tubing equals a louder exhaust. But larger diameter doesn't necessarily mean more power. For a 300hp engine, dual 2" or a single 3" can flow more than enough to prevent any exhaust restriction. Running larger diameters than that just means it's louder.