Eisenmann Cat-Back Exhaust for 2008+ BMW Z4 23i/30i/35i [E89] Dual Exit or Quad Tips

Reduced Backpressure
Eisenmann Exhausts reduce engine heat and backpressure and improve exhaust scavenging from the combustion chamber. They also minimize the power robbing effects of the OEM system to restore torque and horsepower to the engine.

Why is Backpressure Bad? 
Problem 1: Backpressure is a typical feature of an exhaust system. The backpressure on the exhaust flow can help to reduce sound, but at the same time, it limits engine power. This power reduction comes from an inefficient burn in the combustion chamber where spent exhaust gasses are backed-up into the combustion chamber and contaminate the next burn cycle. 
Problem 2: A second problem associated with backpressure is heat build-up. This occurs in the OEM style chamber muffler. Hot exhaust gasses are forced through louvers and into dead-end chambers. The heat builds up in the muffler and then backs itself up through the entire exhaust system to the exhaust manifold and engine. This heat retention causes damage to the muffler as well as the catalytic converter, the system tubing, the manifold and gaskets. Even ignition wires can burn up due to an overheated, inefficient exhaust system.

How do Eisenmann Exhausts Solve the Problems of Backpressure? 
Eisenmann reduces the backpressure while maintaining a rich powerful performance tone. Annoying exhaust frequencies are dampened with a dense wall of acoustical absorbing material. The straight-through design prevents excessive heat retention allowing the entire system to run cooler and last longer.