Cold Start Emission Characteristics and Its Effects on Real Driving Emission Test

Abstract

Worldwide harmonized light vehicles test cycle (WLTC) and real driving emission (RDE) tests were conducted for a light duty vehicles equipped with a gasoline direct injection (GDI) engine in accordance with the China 6 emission regulation of light-duty vehicles. Results show that compared to the cold WLTC test, the emissions of CO, NMHC, THC, PM, PN and NOx from a hot WLTC test are reduced by 91%, 71%, 61%, 39%, 37% and 27%, respectively. For RDE test, when calculating the cold start phase, the emissions of CO, PN and NOx are 24.2%, 2.2 and 3.4% higher than the emissions when excluding the cold start phase. CO2 emission from a hot WLTC is lower than that from a cold WLTC. Especially in the low speed phase, CO2 emission from a hot WLTC is 14% lower than that from a cold WLTC. When using CO2 emission from a cold WLTC and a hot WLTC respectively for move average window (MAW) calculation, the result shows that CO2 value has little effect on the conformity factor of each emission, but has a significant effect on verification of trip completeness and normality.