The control of exhaust emissions is a multi-system task. The multiple systems involved are the oxygen sensors, the EGR (Exhaust Gas Return) valve, the catalytic converter and the muffler/tailpipe.
The oxygen sensors help in the control of exhaust emissions by sensing if there is either too much oxygen or too much combustible fuel being released from the engine in the exhaust gas. Depending on whether the engine is burning too rich or too lean the cars computer will adjust the air/fuel mixture allowed at the intake system.
The EGR valve aids in the control of exhaust emissions by measuring the amount of combustible vapors being released from the cylinders at the point of the exhaust manifold after the combustion process but before the exhaust gasses have reached the main line of the exhaust system. It is determined there is a high enough level of combustible vapors contained within the exhaust gasses to support combustion, the EGR valve will return a portion of the exhaust gasses to the cylinders for combustion through the intake system.
The catalytic converters role in the control of exhaust emissions is to catalyze the hydrocarbons and carbon monoxide in the exhaust gasses. The catalytic converter is the box with the appearance of a muffler installed in the exhaust line after the exhaust manifolds, EGR valve and oxygen sensors, but before the muffler/tailpipe. The catalytic converter consists of a chamber containing platinum or palladium pellets or honeycomb design. When the exhaust gasses pass through the catalytic converter and across the chamber with platinum or palladium pellets or a honeycomb design the hydrocarbons and carbon monoxide are catalyzed into carbon dioxide and H2O.
A muffler is usually located under the car near the bumper at the rear; semi or diesel trucks regularly use a vertically mounted pipe system on the cab. A muffler consists of a box usually constructed with rows of baffles designed to evaporate the H2O catalyzed in the catalytic converter and one or more tailpipes used to reduce noise pollution.
The exhaust system of an automobile is the last system in the defense against harmful emissions and pollution of the Earths atmosphere. The exhaust system does have multiple tasks or more specifically multiple smaller systems that together work for the control of exhaust emissions.
It is very important to have a properly functioning exhaust system if you wish to help limit, reduce or even eliminate the pollution of the Earths atmosphere and stop global warming. If your exhaust system on your car is not functioning properly, you will be contributing to the destruction of Mother Earth.