Cross Overs
Now we move into cross overs. On an asymmetrical true dual exhaust system a REAL true dual exhaust is one of the least recommended configs to run. The reason being that one side of the engine has to work harder to move the same amount of gas out of the system, hurting performance. Scavenging doesn't happen either, also going to be covered later.
The 2 cross over choices for true duals is the H-pipe and the X-pipe. For SISO's and SIDO's, the only choice is the Y-pipe.
The H-pipe
The H-pipe is the simplest, and cheapest cross over for the true dual configs. All that's needed is 2 holes cut out of each pipe and a connecting pipe welded up to those holes. It's simple and straight to the point. Scavenging does occur with an H-pipe, but it's not nearly as effective as an X-pipe, but it's a hell of a lot better than REAL true duals.
H-pipes on a symmetric exhaust helps promote good top end power because most of the exhaust gases are pushed passed the actual cross over pipe, making for a smooth exit. But this certainly is not the case on an asymmetric system. One side of the system still has a longer journey to make than the other, making that side of the engine have to work harder than the other.
The X-pipe
The X-pipe is the pinnacle of crossovers. They offer the best overall performance on a true dual config. X-pipes perform the best because of how both streams of exhaust gasses are forced into each other. This increases scavenging which increases power and torque.
Sound-wise, many top members prefer X-pipes due to the smoothness. X-pipes have a less choppy sound compared to REAL true duals and H-pipes.
