In order to achieve desired sound volume and tone Dinan felt the tubing was enlarged to 83 mm. (vs 80 mm. stock) to allow freer flow throughout the entirety of the system. The larger tubing is fed into a muffler that is typical of all Dinan exhaust design and utilizes absorption and reactive technologies designed to improve exhaust flow and reduce back pressure. The combination results in increased power output and a great sporty sound that is civilized when you want it to be, and pleasantly aggressive under hard acceleration. This is partly courtesy of the retained computer controlled exhaust valves that limit noise during low speed driving and open fully during high-load conditions to allow free flow and greater sound as the bulk of the gases are bypassing the muffler. Like all Dinan exhausts, our M5 free flow exhaust is engineered to reduce low-RPM drone so the cabin o
