Methodology for the analysis of a 4-stroke moped emission behaviour

Mopeds are popular means of transportation, particularly in southern Europe and in eastern and southern Asia. The relative importance of their emissions increases in urban environments which host large fleets of mopeds. In Naples, for example, mopeds make a considerable contribution to HC emissions (about 53%), although the percentage of mopeds (12.4%) in the total circulating fleet is lower than that of other vehicle categories. This study presents a method for analysing the influence of kinematic parameters on the emission factors of mopeds during the ‘‘cold-start’’ and ‘‘hot’’ phases of elementary kinematic sequences (speed-time profiles between two successive stops). These elementary sequences were obtained through appropriate fragmentation of complex urban driving cycles. In a second step, we show how to estimate, for the whole cycle, the duration of the cold phase and the relevant time-dependence function. The method was applied to analyse the regulated exhaust emissions (CO, HC, NOX) of a 4-stroke moped (Euro 2) tested on a dynamometer bench. The experimental data were compared with ARTEMIS and COPERT emission factors, two of the emission models available in Europe to calculate road traffic emissions.