exhaust

exhaust gases from an internal-combustion engine are passed to attenuate (reduce) the airborne noise of the engine. To be efficient as a sound reducer, a muffler must decrease the velocity of the exhaust gases and either absorb sound waves or cancel them by interference with…

…variety of systems for controlling emissions from all these sources have been developed.

…combustion of hydrocarbons in the exhaust), exhaust-gas-recirculation systems, manifold reactors, fuel injection, and unitized ignition elements.

Because emissions from internal-combustion engines are proportional to fuel consumption, a full bus will produce less pollution per person-trip than an automobile. Finally, because they are operated by professional drivers, buses have a lower accident rate than automobiles. Electric rail rapid transit trains produce even less…

Tailpipe emissions standards for motorcycles continue to be strengthened. In 1980 the U.S. Environmental Protection Agency (EPA) first regulated new motorcycle hydrocarbon emissions, requiring motorcycles to emit less than 5.0 grams per km (0.3 ounce per mile) of highway driving. California and the…

…for progressive improvements in truck emissions (based on vehicle weight and engine type) between 1994 and 1997. On Dec. 21, 1999, a new schedule was adopted, known as the Tier 2 standards (with the earlier provisions termed Tier 1), and was phased in between 2004 and 2009. California emission standards…