Exhaust System Key Components

     Exhaust manifold

    The exhaust system really starts at the exhaust header (also known as the exhaustmanifold). The header looks like a series of adjacent tubes stuck together（though it'soften made of heavy-duty cast metal). It collects the exhaust directly from the engine, soeach opening mates up with one of the engine's exhaust ports，with flanges that form a tight seal to prevent exhaust from escaping. From here，the exhaust begins its flowthrough the various pipes and other components.

    Gaskets

    The gaskets that are fitted between each pipe play a very important role. It's difficult，if not impossible，to form a flawless metal-to-metal seal，so gaskets are sandwiched between each connection to prevent the poisonous gases from escaping prematurely.They're made of fiber or other heavy-duty, heat resistant materials，which have justenough flexibility to compress slightly when the pipes are clamped tightly together. Thishelps form a tight seal.

    Muffler

    Themuffler is another key part of the exhaust system.

    Inside a muffler, you'll find a deceptively simple set of tubes with some holes inthem. These tubes and chambers are actually as finely tuned as a musical instrument.They are designed to reflect the sound waves produced by the engine in such a way thatthey partially cancel themselves out.

    Catalytic converters

    In the catalytic converter, there are two different types of catalyst at work, areduction catalyst and an oxidation catalyst. Both types consist of a ceramic structure coatedwith a metal catalyst, usually platinum，rhodium and/or palladium. The idea is to create astructure that exposes the maximum surface area of catalyst to the exhaust stream, whilealso minimizing the amount of catalyst required, as the materials are extremely expensive.Some of the newest converters have even started to use gold mixed with the moretraditional catalysts. Gold is cheaper than the other materials and could increase oxidation,the chemical reaction that reduces pollutants，by up to 40 percent. Most modern cars areequipped with three-way catalytic converters. As the exhaust passes through the cat，thelevel of chemicals should be reduced enough to comply with government regulations.