Analytical-experimental analysis of last generation medium-size motorcycles emission behaviour under real urban conditions

Mopeds and motorcycles are broadly used and represent a large share of motorized vehicles, above all in the urban environment of Asia and Europe; as a consequence, the relative contribution of the emissions of powered two-wheelers to the total air pollution has increased considerably in the last years. For this reason, an experimental investigation was performed on the regulated pollutants: CO (carbon monoxide), HC (unburned hydrocarbons), and NOX (oxides of nitrogen) emissions were evaluated in the exhaust of a motorcycle with a displacement of 250 cm3, equipped with catalytic converter and electronic mixture control. This vehicle was tested on a dynamometer bench both on a Type-Approval test cycle and on real-world test cycles. The study also presents a method to analyze, during different driving cycles, the influence of the speed profile on the emission factors of the motorcycle, through the elementary kinematic parameters of basic sequences, which were achieved through appropriate fragmentation of composite urban driving cycles. Examination of the results obtained in this study has recognized the kinematic parameters that cause higher CO and HC emissions. By using this statistical method, the vehicle emission assessment is meaningfully improved if compared to the models that are mainly centred on the average speed of the test cycles. The statistical processing results of the experimental data were also compared to current emission models for calculating emissions from road traffic in Europe.