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

The test results showed that carbon monoxide (CO) and total hydrocarbon (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 °C 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.