A miniature Portable Emissions Measurement System (PEMS) for real-driving monitoring of motorcycles

Abstract. We present an exploratory study carried out with a new miniature portable emission measurement system (Mini-PEMS) specifically designed at the Technical University of Liberec (CZ) for applications on 2-wheeler vehicles owing to its reduced size (45 x 30 x 20 cm) and weight (≈ 15 kg). It measures the exhaust gas concentrations of hydrocarbons, carbon monoxide and dioxide with non-dispersive infrared method, nitrogen mono- and di-oxides and oxygen using an electrochemical cell. In addition, the instrument acquires the engine speed, the manifold absolute pressure, the inlet and exhaust gas temperature, the geo-localization and vehicle speed. The exhaust mass flow rate is calculated from engine and emission data. The Mini-PEMS was validated on three 2-wheelers (1 moped and 2 motorcycles) against laboratory-grade instrumentation in the Vehicle Emissions Laboratory of the European Commission in terms of measured concentrations, exhaust flow, fuel consumption and mass emission of pollutants. The mean absolute deviations of gas concentrations were 8 % for HC, 8 % for CO, 13 % for NOx and 2 % for CO2 while the mass emissions (which include the exhaust flow determination uncertainty) were 7 % for HC, 7 % for CO, 9 % for NOx and 5 % for CO2. An agreement of 2 % was achieved between the fuel consumption measured in the laboratory and calculated by the Mini-PEMS. As an application, the instrument was tested on board of the vehicles during on-road trips. The emissions measured on-road were consistent among repeated runs, with differences between laboratory and on-road tests much larger than those between Mini-PEMS and laboratory. We found similar or larger HC and NOx real-driving emissions, larger CO from motorcycles and smaller for the moped. Considering its size and weight, the Mini-PEMS proved to be an efficient tool for vehicle monitoring, research and development and could be tested for in-service monitoring applications related to carbon monoxide and nitrogen oxides emissions. A tentative approach to characterize particulate mass and particle number was presented and compared to the existing non-volatile particle number protocol.