Keywords: motorcycles, exhaust gas, VOC, NMOG, ozone, ozone-forming potential, vehicle emissions, pollution emissions, real world driving, toluene, xylene, ethene, propene, two-stroke engines, four-stroke engines
The emission profile of volatile organic compounds (VOC) and the ozone-forming potential (OP) of the exhaust gas of six in-use motorcycles (four 4-stroke- and two 2-stroke-engines) were determined. The motorcycles were tested on a chassis dynamometer in a real-world driving cycle. The analysis involved the C2–C12-hydrocarbons as well as the aldehydes and ketones. Additionally, the regulated THC and NOx emissions were measured according to the test procedure for type approval (ECE 40). Two vehicles did not fulfil the THC emission standard, whereas all vehicles met the requirements for NOx emission. The aromatic fuel components toluene and xylene, and the combustion products ethene and propene contributed most to the OP of the VOC emission. The highest OP was found with the 2-stroke engines. The VOC profile of the emissions varied with vehicle and driving conditions. The reactivity of the exhaust gas, defined as gram ozone per gram of non-methane organic gases (NMOG), increased with vehicle speed.