Studies on the correlation between ethanol-gasoline blends and pollutant emissions of small engine motorcycles are scant. This study examined the effects of ethanol-gasoline blends, containing various ethanol contents, on air pollutant emissions from two four-stroke fuel-injection motorcycles without engine adjustment. Three test blends, separately containing 15 (E15), 20 (E20), and 30 vol% (E30) ethanol in gasoline, were used to power the test motorcycles. Commercial unleaded gasoline was used as the reference fuel (as RF). The motorcycles were tested on a chassis dynamometer by using the Economic Commission for Europe test cycle. The target pollutants investigated in this study included criteria pollutants, volatile organic compounds (VOCs) and six species of organic air toxics. The results revealed that the emissions of CO, THC, total VOCs, alkanes, alkenes, and aromatic groups reduced when the ethanol-gasoline blends were used to fuel the motorcycles. E30 demonstrated approximately 1.2-fold increases in carbonyl group emissions compared with RF. Emissions of the target air toxics demonstrated a reduction potential on benzene, toluene, ethylbenzene, and xylene (BTEX), but increased the emissions of formaldehyde and acetaldehyde by 65% and 330%, respectively. Results also showed that the emission changes from fuel-injected motorcycle were generally smaller than the value of carburetor motorcycle. Fuel injection engine fueled with ethanol-gasoline blends may lead to emission reductions to CO, THC, and BTEX.
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