Cold emissive behaviour of motorcycles

Cold start effect is one of the most significant item for real world emissions evaluation: engine and after-treatment system transient behaviour leads to high levels of pollutants, generally exhausted in urban driving mode. In this paper, literature data referred to cold transient are summarized for some motorcycle classes. The main results of an experimental activity, performed to characterize the cold emissive behaviour of a 125 cc 4-stroke Euro 3 motorcycle during different driving cycles, are then presented. Finally, a simple calculation procedure for the evaluation of cold instantaneous emission factors as a function of travelled distance during the transient and the cold additional emission on a trip of fixed length is proposed and discussed.