Ideal Pipe Diameter for Performance Exhaust Systems

Video Transcript

"Hi I'm Doug. I work with twenty great guys in St. Louis at Doug Jenkins Custom Hot Rods, and we're going to do some work for you today on Expert Village. In this next clip let's discuss in careful detail the truth about exhaust pipe diameter and the purpose of exhaust pipe. Obviously, pure and simple the purpose of exhaust pipe is to get the exhaust out of the back of the car. You put a muffler on it so it's not as loud. Those two things though, what about like a funny car just running open headers, well if you build your engine exactly right you can run open headers and get maximum power. But for street use, you're not just talking zero to three hundred miles an hour. We're talking a little bit of torque as you leave a stoplight. We're talking how nicely it idles, how much noise the car makes, how much ground clearance it has, there's a bunch of factors that go into the choice of an exhaust system. I made a comment earlier that we're using three inch pipe on this job because it's a 620 horse motor, you want to get lots of exhaust out fast. So we start with three inch pipe, but you can see in the corners where Dave is bending the pipe, that it deforms the diameter of the pipe and necks it down smaller than three inches. But that's part of why we started with three inches, two and a half would work fine for this application. You can see he's got a wooden block in there; he's trying to do a compound bend there where it turns real sharp, and in order to not destroy his earlier bend with the corner of the pipe bender he's got the little piece of plywood in there. We're willing to tolerate the pipe deformation from a three inch pipe in an application like this because of simple budget concerns."