The speciation of volatile organic compounds (VOCs) from motorcycle engine exhaust at different driving modes

This study investigated the emissions of volatile organic compound (VOC) from motorcycle engine exhaust at different driving modes on a dynamometer. The speciations and the ozone formation potential of VOC samples also had been investigated by GC/MS and maximum increment reactivity (MIR), respectively. Both brand new and in-use motorcycles were tested in this study. The tested motorcycles include 2-stroke and 4-stroke engines. There are totally 48 VOC compounds identified in this study. Only the VOC species with C₃-C₉ were identified successfully. Experimental results indicated that isopentane, toluene, m,p-xylene, n-pentane, 2-methylpentane, 3-methylpentane, benzene, n-heptane and methylheptane were the major VOC speciations in the motorcycle engine exhaust. The amount of VOC emissions of the in-use 2-stroke motorcycles was 5 times that of the new 2-stroke motorcycles and the in-use 4-stroke motorcycles was 15 times that of the new 4-stroke motorcycles during the whole cycle. The amount of VOC speciation concentration during idle and deceleration stages was higher than those during the acceleration and cruising modes. However, the emission rate of VOCs at various driving modes tested on a dynamometer had not been precised enough due to the inconsistent variation of volume efficiency of motorcycle engine. These data shows a clear distinct emission rate of VOC at various driving modes. Besides, alkanes and aromatics were the major VOC speciation groups in the motorcycle engine exhaust. The amount of VOCs contributed from 23% to 76% THC for the four types motorcycle. Great variation of VOC/THC were found among new and in-use motorcycle. The ozone formation potential of a 2-strokes engine was higher than that of a 4-stroke engine. The ozone formation potential of in-use motorcycles were also clear higher than those of new motorcycles.