Automobile

After the fuel is burned in the pistons, the gases and heat created must be discharged from the cylinder to make room for the next infusion of fuel. The exhaust system is also responsible for reducing the noise caused by the explosion of the fuel.

Exhaust gases are discharged from the cylinder through an exhaust valve. The exhaust gathers in an exhaust manifold before eventually being channeled through the exhaust pipe and muffler and finally out the tailpipe and away from the car. The muffler is constructed with a maze of what are called baffles, specially developed walls that absorb energy, in the form of heat, force, and sound, as the exhaust passes through the muffler.

The burning of fuel creates additional byproducts of hazardous gases—hydrocarbons, carbon monoxide, and nitrogen oxide—which are harmful both to the engine's components and to the environment. The emission control system of a car is linked to the exhaust system, and functions in two primary ways. The first is to reduce the levels of unburned fuel. This is achieved by returning the exhaust to the fuel-air mixture injected into the cylinders to burn as much of the exhaust as possible. The second method is through a catalytic converter. Fitted before the muffler, the catalytic converter contains precious metals that act as catalysts. That is, they increase the rate of conversion of the harmful gases to less harmful forms.