Petrol passenger car emissions calculated with different emission models

A comparative study was made on emission factors from different emission models focusing on the gasoline ECE 15/04 and catalyst cars with engine sizes between 1.4 and 2 l. Carbon monoxide, VOC and NOx emissions were evaluated from three models: COPERT II, German Workbook, the DTU model and Danish measurements. In addition, the study examined if a reduced catalyst efficiency at high speeds in the DTU model, causing increased emissions, could be verified. The result of using the different models for macro-scale emission calculations was illustrated with an emission calculation example for the two vehicle types. For catalyst cars at high speeds, the CO, VOC and NOx emission factors in COPERT II indicate a reduced catalyst efficiency, but this tendency is not verified by the Danish measurements. Only in the case of NOx, the German Workbook factors suggest a reduced catalyst efficiency. The emission factors vary between the models. Stemming from this difference, the computed total CO emissions are 50–75% higher in the DTU model, compared with the other models. The Danish VOC and NOx total emissions are about 40 and 50% lower, respectively, than the emissions obtained with the other models.