How Your Vehicle Works

Exhaust Systems

Your exhaust emission system really starts at the front of your car, right behind your engine. Exhaust pipes connect to the cylinder heads, where they collect exhaust gases. As the gases move through the system, they're first analyzed by oxygen sensors, then refined by the catalytic converter and, finally, muffled by the muffler. So by the time those gases leave the vehicle, your emission system has made your car run smoother, cleaner, and quieter.

Exhaust manifold gaskets may be made of embossed steel, sometimes in multiple layers. These gaskets may also be made of high-temperature fiber material, graphite, and ceramic composites, among others. Some gaskets use a combination of different materials. Other types of exhaust gaskets include flange gaskets and ring gaskets located at various connection points in the exhaust system. These gaskets are usually made from the same types of materials as exhaust manifold gaskets.

An exhaust manifold gasket seals the exhaust manifold to the cylinder head. On V6 and V8 engines, there are two exhaust manifolds and therefore require two manifold gaskets. An exhaust manifold gasket seals the connection between the manifold and cylinder head. This prevents exhaust leakage out of the connection and also ensures that all exhaust gas will flow through the catalytic converter for treatment. Flange and ring gaskets seal other connection points in the exhaust system, such as between the exhaust pipe and exhaust manifold.

Made of cast iron or tubular steel, the exhaust manifold mounts to the exhaust side of the cylinder head. An exhaust manifold gasket is used at the connection to ensure a good seal. Engines with their cylinders arranged in-line usually have one exhaust manifold. Engines with V-type cylinder arrangements, like the V6 and V8, have two separate exhaust manifolds, one mounted to each cylinder head.

The exhaust manifold routes the exhaust gases leaving the cylinder head to the exhaust system. As such, the manifold also serves as a connection point for the exhaust pipe. Depending on engine configuration and the number of exhaust manifolds, there may be two exhaust pipe connections. Depending on the year, make and emissions equipment installed on the vehicle, the exhaust manifold may also serve as a mounting location for hardware of the air injection system or for an oxygen sensor. Also, some exhaust manifolds may still include a heat riser valve, controlled by a temperature-sensitive spring. This valve is designed to help divert hot exhaust gas through a separate passage in the intake manifold to aid in better warm-up driveability.

Exhaust pipe is a general term for several different pipes used throughout the exhaust system. Although configurations vary with different makes, models and engines, there is usually a front exhaust pipe connecting the exhaust manifold to the catalytic converter, an intermediate exhaust pipe connecting the catalytic converter to the muffler, and a tailpipe connected to the outlet of the muffler and serving as the exhaust outlet. Exhaust pipes may be made of standard or stainless steel.

Exhaust pipes route exhaust gas away from the engine, through the catalytic converter and muffler and out the rear of the vehicle. As a result, pollution and sound are reduced, while ensuring safety by directing exhaust gas away from the vehicle.

The muffler reduces and changes engine exhaust sound and tone. When properly matched to the engine, a muffler will not impair engine performance due to exhaust backpressure, which is simply the resistance to exhaust flow.

A standard or stainless steel casing containing an array of baffles and other sound-insulating material to reduce exhaust noise. Some cars may use several mufflers, or a secondary muffler called a resonator.

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[Lots more information about mufflers]
[Lots more information about catalytic converters]
[Even more information about catalytic converters]
[Lots more information about CO2 and other greenhouse gasses]


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