RDE-Compliant PEMS Testing of a Gasoline Euro 6d-TEMP Passenger Car at Two Ambient Temperatures with a Focus on the Cold Start Effect

European Union RDE (real driving emissions) legislation requires that new vehicles be subjected to emissions tests on public roads. Performing emissions testing outside a laboratory setting immediately raises the question of the impact of ambient conditions - especially temperature - on the results. In the spirit of RDE legislation, a wide range of ambient temperatures are permissible, with mathematical moderation (correction) of the results only permissible for ambient temperatures <0°C and >+30°C. Within the standard range of temperatures (0°C to +30°C), no correction for temperature is applied to emissions results and the applicable emissions limits have to be met. Given the well-known link between the thermal state of an engine and its emissions following cold start, ambient temperature can be of great importance in determining whether a vehicle meets emissions requirements during an RDE test. This paper reports the results of full RDE-compliant on-road emissions tests performed on a Euro 6d-TEMP passenger car with a direct injection spark ignition engine and a gasoline particle filter. Testing was performed at two temperatures, both lying within the “standard” temperature range for RDE testing: +25°C and +8°C. Regulated gaseous emissions, particle number and CO₂/fuel consumption results are presented and discussed. Overall, as expected, emissions following cold start were significantly higher at the lower test temperature. Nevertheless, the long distance covered during RDE tests (~70-100 km) and their urban phases (>16 km, often ~25 km) weakens the impact of this effect. Some simple mathematical analyses of the results from various portions of the trip are presented.