Emission Characterization of In-Use Diesel and Gasoline Euro 4 to Euro 6 Passenger Cars Tested on Chassis Dynamometer Bench and Emission Model Assessment

ABSTRACT

This paper focuses on CO₂ and regulated pollutants (NO_x, HC, CO, PM) emitted by eight Euro 4–6 gasoline and diesel vehicles with six different technologies. The emission factors were repeatedly measured on a chassis dynamometer bench using Artemis Urban with cold and hot start, Road and Motorway, WLTC and NEDC driving conditions. The influence of driving conditions and approved driving cycles on pollutant emissions was also investigated. The measured emission factors for regulated compounds were compared to the corresponding emission factors of the COPCETE emission model developed by the French Ministry of Ecology. The results indicate that the NEDC cycle, used for type-approval of emissions of regulated compounds, leads to underestimation of CO₂ (9–23%) and NO_x (1.2 to 2 times) emissions and overestimation of CO and HC (2 to 5 times) in relation to the Artemis cycles, which are real-world simulation driving cycles. The WLTC cycle for the worldwide harmonization of vehicle emissions shows similar HC, NO_x and CO emissions with the Artemis average cycle within uncertainty of the measurements. The NO_x emissions measured were 1.6 to 8 times greater than the type-approval limits. These high NO_x emissions produced by all the diesel vehicles tested under real-world driving conditions could serve as particle precursors and increase secondary organic aerosol formation. They are also indicative of the significant cause for concern regarding urban air quality and the increase in the portion of Euro 5 and 6 diesel vehicles in France's vehicle fleet. Regarding emission factor assessments, the emission levels measured are overall in fair agreement with the COPCETE predictions within uncertainties for CO₂ and regulated pollutants. Updating the database is vital in order to be able to produce more representative emission factors and better evaluate the health and environmental effects from vehicle emissions.