Two of my friends have '04 F-250 4x4 Superduties. One is a 5.4, the other is the V-10. They both have the same deal on the Y pipe. The right leg of the pipe is ~2". But, the last inch or two is reduced to ~1 1/4" diameter pipe, as it tees into the main pipe coming from the left side. It has to be a major restriction, especially on the V-10. Also, the right leg loops around needlessly, instead of taking a nearly straight path into the main part of the front ("Y") pipe. It makes no sense. Does anyone know why it's like that? Would there be a benefit to correct it? I'm not sure if the F-150s are the same. Any info would be appreciated. Dave C.

 

I would have to guess that the one pipe that loops around for extra length of pipe for no obvious reason would be so that both sides of the y-pipe have as near equal lengths as possible. The reason for this is so that the exhaust pulses coming down each length of pipe will blend together at the Y as equally spaced as possible. This in turn helps the following pulse to be drawn out by suction, and so on, and so on, etc. This is often used on high-performance headers, so that all 4 legs of a header are the same length, giving a major boost in torque. Each exhaust pulse gets help from the previous pulse, smoothing the flow downstream and increases efficiency of the system. As for the restriction, no answers here.

Denis.