Automobiles and Emission Control

Categories : Gembing


Automobiles are four-wheeled vehicles designed primarily for passenger transportation, commonly propelled by an internal combustion engine using a volatile fuel. Modern automobiles are complex technical systems with subsystems that have specific design functions. These include the body, chassis, engine, transmission, drive system, controls, safety systems, and emission-control systems.

Emissions are a major concern of national policy makers and vehicle owners, and emissions standards have become increasingly stringent over the years. Regulations rely on the results of dynamometer tests that simulate highway driving conditions to determine if vehicle engines meet emission standards. The approach to these tests varies among regulatory agencies, and the most significant difference is in the method used for measuring exhaust emissions.

Test procedures are based on two basic philosophies. The first, employed by the Environmental Protection Agency (EPA), involves measuring emissions from the engine and from the vehicle under actual driving conditions. The second, utilized by most of the European Economic Community and Japan, consists of repeated repetitions of a driving cycle that is a composite of various typical driving modes.

Cars have become the primary means of family transportation in many parts of the world, with more than three trillion miles being traveled annually by cars and light trucks. They are also the largest source of air pollution in the United States, and emissions from these vehicles contribute significantly to national air quality problems. Emissions can be reduced by changing the way the engine operates, such as through a better mixture or spark timing, or by using catalytic converters, which can remove nitrogen oxides from the exhaust.