Comparison of Tail-Pipe Emissions from Motorcycles and Passenger Cars

Abstract

The tail-pipe emissions of carbon monoxide (CO), nitrogen oxides (NO_x), total hydrocarbons (THC), and speciated volatile organic compounds (VOCs) from the exhausts of cars and motorcycles with and without catalysts in the Federal Test Procedures (FTP) and European Community Emission (ECE) driving cycles were measured and compared. Compared with catalyst cars, motorcycles were found to emit 12 times as much THC and CO for every kilometer driven. Cars and four-stroke motorcycles emitted much higher levels of NO_x than two-stroke motorcycles. Motorcycle emission rates of benzene were lower than those from noncatalyst cars but higher than those from catalyst cars. The catalyst’s reduction efficiency in motorcycles was only one-half that in cars. Among the exhaust components, the reduction efficiencies of aromatics were lower than those of THC and CO by the catalysts. For most pollutants, the greatest reduction of emissions by the catalysts occurred in Phase 2 of the FTP driving cycle. In this study, the VOC profiles in the emissions were found to be relatively rich in benzene.