Benefits and Impacts of Multi-level Emission Standards on the Fuel Economy Characteristics of Small and Large Cars

Book excerpt: A brief review of the small car vs large car fuel economy and emission scenario was conducted to determine whether it is meaningful to implement multi-level emission regulations (different values for small and large cars) to encourage or forces the use of catalytic converters on smaller cars, and by so doing improve the overall fuel economy of the total fleet while at the same time reduce overall emissions. The results of this review showed that: the 1975 to 1976 federal HC standard (1.5 gr/mi) is sufficiently low to effectively force the use of catalysts on larger cars (4000-lb inertia test weight and above) to avoid fuel economy losses, but not sufficiently low to require them on all smaller cars (3500-lb class and below). However, the 1975 to 1976 California HC standard (0.9 gr/mi) is sufficiently low to do so, as evidenced by the fact that essentially all California cars do use catalysts; whether or not small or large cars are equipped with oxidation catalysts, NOx standards below the current federal level (3.1 gr/mi) and California level (2 gr/mi) will act to reduce vehicle fuel economy, although small cars are slightly less sensitive in this respect; to meet the projected federal and California HC standard of 0.41 gr/mi, both small and large cars will be forced to use catalysts, since this is the only available emission control technique for the conventional spark ignition engine; and to ensure the fuel economy and emission benefits of catalysts, ERDA need only support the implementation of the proposed HC standard of 0.41 gr/mi. Making the federal standard the same as the California one would also produce this result.