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

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 two-wheeler vehicles owing to its reduced size (45cm x 30 x 20cm) and weight (approximate to 15 kg). It measures the exhaust gas concentrations of hydrocarbons and carbon mono- and dioxide with a nondispersive infrared method and nitrogen mono- and dioxides and oxygen using an electrochemical cell. In addition, the instrument acquires the engine speed, manifold absolute pressure, inlet and exhaust gas temperature, geo-localization, and vehicle speed. The exhaust mass flow rate is calculated from engine and emission data. The Mini-PEMS was validated on three two-wheelers (one moped and two 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 the vehicles during on-road trips. The emissions measured on the road were consistent among repeated runs, with differences between laboratory and on-road tests much larger than those between the Mini-PEMS and laboratory. We found similar or larger HC and NOx real-driving emissions and larger CO emissions from motorcycles and smaller ones 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 filter method and nonvolatile particle number protocol.