Exhaust Emissions from an SUV with a Spark-Ignition Engine Tested Using EU and US Legislative Driving Cycles and EU RDE Procedures 2021-01-0616

Despite an overall trend towards harmonization in vehicle regulations, regional differences persist in the area of exhaust emissions and fuel economy. The test procedure employed can exert a significant impact on the results obtained. In this paper, the EU and US type approval procedures for light duty vehicles are briefly compared and results obtained from several types of test procedure are presented. Specifically, emissions tests were performed on a single SUV which met US Tier III emissions limits. The vehicle featured a conventional, naturally aspirated spark ignition engine with indirect fuel injection and an aftertreatment system consisting of three-way catalysts with no dedicated particulate filtration device. The vehicle’s engine displacement, total mass and power-to-mass ratio were relatively representative of the upper end of the US market, but represented an outlying vehicle in terms of the characteristics of the EU fleet. The following test procedures were used: the current EU test procedure (WLTP) and previous EU test procedure (NEDC); three of the US test procedures (FTP-75, HWFET, US06); and finally on-road emissions testing performed according to the EU RDE procedure. Laboratory testing included measurements of such as particulate matter and certain unregulated pollutants. As expected, emissions and fuel consumption behavior differed with the test cycle employed. The test vehicle was found to meet all EU emissions requirements, including those relating to RDE. Characteristics of the various test procedures and their impact on the emissions results are discussed, with a special focus on cold start behavior and urban driving conditions.