PARTITIONING OF NOX EMISSIONS FOR GASOLINE PASSENGER CARS AND LIGHT DUTY TRUCKS

Traffic is the main source of anthropogen nitrogen oxide (NOx) emissions. Nitrogen oxide consists of nitric oxide (NO) and nitrogen dioxide (NO2). NO2 is an irritant, destroys cells of plants and affects visibility. In combination with volatile hydrocarbons, NOx plays a major role in the formation of ground ozone. NOx and NO emissions from six gasoline passenger cars and ten gasoline light duty trucks of the Euro-2 generation were measured in this work. The measurements were carried out in the NEDC and FTP75 cycles, in the German Bundesautobahnzyklus and in four Swiss real-world cycles. All vehicles were provided by private owners and brought directly from the traffic to the chassis dynamometer. In order to obtain results which would be as realistic as possible, no servicing was carried out. Depending on their mass, gasoline light duty trucks of the Euro-2 generation have a legal HC+NOx limit which is 20 to 40% higher than for gasoline passenger cars of the same generation. The measurements show that the light duty trucks cause about eight times higher NOx emissions in the Swiss real world compared to the passenger cars. However, this cannot originate from the higher engine load alone; there have to be major differences in engine construction, engine tuning or in the layout of the exhaust gas aftertreatment system. The catalyst efficiencies of the light duty trucks are significantly lower than those ones of the passenger cars. Apart from this difference in total NOx emissions, it is interesting to note that the partitioning of NO and NO2 differs for passenger cars and light duty trucks. About 4.3 percent of the NOx emissions from passenger cars is emitted as NO2, without a significant influence on the velocity pattern driven. The light duty trucks show a strong dependence on the velocity pattern. On average they emit 17.6 percent NO2 but this figure goes up to 41.1 percent for freeway driving. For the covering abstract see ITRD E122175.