Low-temperature cold-start gaseous emissions of late technology passenger cars

The control of exhaust emissions from modern vehicles is based on the use of after-treatment devices typically consisting in different types of catalysts. The efficiency of catalytic systems however strictly depends on their temperature, achieving certain effectiveness in reducing emissions only above the light-off temperature. This generally leads to elevated emissions during cold-start operation, especially under low ambient temperatures. We investigated the gaseous emission performance of thirteen latest technology vehicles over the New European Driving Cycle (NEDC), at 22°C and -7°C test cell temperatures. The test fleet included gasoline vehicles both Port Fuel Injection (PFI) and Gasoline Direct Injection (G-DI) as well as diesel vehicles, amongst which a fully Euro 6 compliant vehicle equipped with a Selective Catalytic Reduction (SCR) system. The test results showed that Carbon Monoxide (CO) and total Hydrocarbons (HC) emissions of gasoline vehicles increased from 2.3 to 11.3 times at -7°C over the Urban Driving Cycle (UDC), remaining however below the current legislative limits by 45% and 65% respectively. Nitrogen Oxides (NOx) emissions of gasoline vehicles at -7° turned out to be either higher or lower than at 22°C, depending on the catalyst’s performance and engine injection strategy. Diesel vehicles without any NOx after-treatment system exhibited increased NOx emissions over both the UDC and Extra Urban Driving Cycle (EUDC) when tested at -7°C. The diesel car with the SCR system showed superior NOx performance only over the second half of the NEDC.JRC.F.8-Sustainable Transpor