I've noticed one or two comments on aftermarket exhausts on the M3 that offer a plausible glitch. Apparently, the M3's "cupped" rear apron and diffuser were designed in conjunction with the factory exhaust. Considering the muffler runs perpendicular to the body's length, changing this shape could lead to an unfortunate side effect in using an aftermarket exhaust. Since this is not the case in most other BMWs, I do not think it has not been fully explored.
Most if not all of the replacement exhausts offer a weight saving compared to the factory's exhaust. Now almost everyone would jump up and yell "Yeah! Weight savings!", but along with the weight savings come along a smaller and/or reshaped muffler. This change in shape, can allow the air under the car to get caught between the diffuser and the muffler, negating any of the weight savings. And in effect, acting like a air brake in the upper speeds.
So if you're looking for an aftermarket exhaust, you may want to look at your perspective exhaust bolted up on an M3. Inspect the gap between the back of the muffler and the diffuser, as well as the actual length of the muffler portion itself.
Seems to make sense to me!
Most if not all of the replacement exhausts offer a weight saving compared to the factory's exhaust. Now almost everyone would jump up and yell "Yeah! Weight savings!", but along with the weight savings come along a smaller and/or reshaped muffler. This change in shape, can allow the air under the car to get caught between the diffuser and the muffler, negating any of the weight savings. And in effect, acting like a air brake in the upper speeds.
So if you're looking for an aftermarket exhaust, you may want to look at your perspective exhaust bolted up on an M3. Inspect the gap between the back of the muffler and the diffuser, as well as the actual length of the muffler portion itself.
Seems to make sense to me!