X pipes work by using the crossover, or X, to draw gasses from one bank using the venturi effect of the other side. The effect is to help the engine ‘breathe’ more easily and is very noticeable above 4000rpm when the balancing butterfly in the manifold opens. There is an increase in power and another benefit is a subtle and very pleasant change in engine note.
'X’ over pipes were discovered during the Winston cup race series. One of the cars seemed to be consistently faster than anything else out there, and it wasn’t until the car in question had a racing accident and turned over that the reason became obvious. ‘X‘ pipes!<