Is Cross-over necessary?
The crossover on an exhaust system has several benefits. In a stock configuration (such as the Softtail), the mufflers are extremely restricted. The crossover allows the gasses from one cylinder to bleed off excess pressure to the other side. This increases performance by decreasing backpressure. Also, a crossover helps decrease exhaust noise by having the second muffler share a percentage of the load. Locating the crossover approximately seven inches from the exhaust valve enhances performance, allowing that seven inches of header pipe to retain good exhaust gas velocity, and reducing the pressure at the crossover. Another benefit of crossover is when you install freer breathing mufflers — they will reduce the intensity of the reversion wave back toward the cylinder. Crossovers located a long way down the system and close to the mufflers (such as with a Dyna) have very little to do with performance and are there mainly to reduce noise.
