Abstract
Amid increased international concern about environmental issues in recent years, new proposals have been presented throughout the world for more stringent exhaust emission standards and fuel economy requirements. This paper discusses technical approaches to reducing hydrocarbon (HC) emissions to extremely low levels, focusing on the low-emission vehicle (LEV) standards proposed by the California Air Resources Board (CARB). The LEV regulations call for a 70-90% reduction in HC emissions from gasoline-engine vehicles. Reducing tailpipe HC emissions requires the application of various engine improvements and the use of reformulated gasoline to lower engine-out HC levels, as well as further enhancement of the catalytic activity level. Moreover, the accuracy of exhaust gas measurement methods must also be improved to measure lower levels of HC concentrations.