During the combustion of fuel, BMW vehicles create gases to include hydrocarbons or the unburned fuel, carbon dioxide, sulfur dioxide, carbon monoxide, nitrogen oxides, phosphorus lead and other metals. These exhaust gases when mix with the air could be harmful. That is why every BMW is equipped with exhaust system that functions to reduce the harm caused by these gases into a lesser and safer air. The exhaust system also reduced the noise created by the combustion inside the engine before it exits the system.

The exhaust system are mainly a series of tubes as pipes that is connected from the engine through the exhaust manifold to the tail pipe- exhaust system part only visible when the vehicle is looked at the rear. As the first part of the exhaust system, the exhaust manifold is a network of tubes connected at the exit passage of each cylinder. It gathers the exhaust gases to manage and direct the flow in to one direction, which is to the tail pipe. Usually made from cast or nodular iron, the exhaust manifold is a contraption that is designed depending on the type of the engine employed in the vehicle and the number of cylinders the engine has. In other words, the number of exhaust manifolds depends on how many cylinders are present.

When the exhaust gasses are gathered from the engine through the exhaust manifold, the process of converting these into lesser and safer air is made at the catalytic converter. After the process, the exhaust now turned in to water vapor and carbon dioxide passes through the resonator which is also called as the mini muffler which silences the exhaust. It is either located before or after the muffler. The air then passes through the exhaust pipe, then to the muffler, and finally to the tail pipe before it mix to the air at the atmosphere.