Simple question, what would flow better-


A. Single 2.5 exhaust without cat

B. Single 3 in exhuast with cat (stock type)

Assuming they both have the same headers and same muffler
what do you guys think?

 

single 3inch with a high flow cat.. hands down.

 

Yeah, the 3" single pipe will flow about as much as a pair of 2.25" duals. It's a simple matter of surface area.

THe 2.5" system will offer better ow end torque and the 3" system will breath better at high RPM. Most 3rd gens, even those with a 305 will like the 3" system. In fact some cars had 3" parts from the factory, but these pipes weren't mandrel bent so they are still restrictive.

 

its actually a matter of cross sectional area....which is what you meant i think anyways,

however, the smaller pipe giving better low end torque is a common misconception.....

this can be true, if you have headers/manifolds that are poor at scavenging.......the smaller tube will increase the pulse signal and help scavenging.....but if you use the correct headers to promote good scavenging....you can open up the pipe as big as you want and you can actually pick up some torque due to the excellent scavenging coupled with the increased flow of the larger pipe.

contrary to popular belief, backpressure is never a good thing, its the exhaust pulse scavenging affect that people are after