also, inside of tubing, air (and water) will flow faster in the center of the tube than on the outer edges near the wall of the tubing/piping. so, just thinking out loud, if you change the shape of the pipe to an oval shape rather than a circle, the flattened walls would cause more tirbulance. i assume the same will go for the transition peice from circular to oval. i wonder if anyone has ever put a flow meter up to this to test the differences. might be more efficient to just dump your exhaust out the side instead of piping all the way to the rear... engineering gurus, please feel free to jump in with your thoughts.
