Reading this thread has really piqued my interest. So yesterday I taped my exhaust pipe up with aluminum foil tape down to about 1". I'd like to say that I noticed an increase in low-RPM torque, but I have no actual data to back that up. What I did notice, however, is that because the tape can flex a little bit over the open pipe, it tends to "flutter" during engine deceleration and actually suck in to the pipe. It also sucks in to the pipe when I shut the engine off too. I am guessing that this has something to do with the mass of air moving at a set velocity through the pipe, creating a low pressure in the pipe when the amount of air produced by the engine is suddenly reduced and the momentum of the moving air tends to continue out the end of the pipe at a set velocity.
Quote:
Originally Posted by Ryland
But the bottom line is, you want to keep your exhaust moving at around 240 feet per second and a larger exhaust pipe is not going to allow that to happen unless you have a much larger volume of exhaust as well, that larger pipe will end up with a much slower charge of exhaust moving down it so I have to wonder what good does that slower exhaust give you?
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This makes me wonder if putting a reduction near the end of the exhaust actually has any effect on the velocity of the exhaust gasses inside the pipe before the reduction, other than simply creating backpressure in the pipe. A stock exhaust system is going to have a series of reductions and expansions anyway (cat, resonator, muffler, tailpipe). The Corsica has a resonator just before the cat, which I'm guessing is probably the best point to terminate the pressure wave from the engine, depending on which RPM and throttle that resonator is designed for. My understanding is that anything after the resonator is simply piping and any change should have nothing to do with pressure wave tuning. That doesn't explain why adding restrictions near the end of the exhaust system would aid in low-end torque. I'm thinking about adding something like the adjustable butterfly valve setup. But WHERE to put it is really the question.