Real World Cold Start Emissions from a Diesel Vehicle 2012-01-1075

This study uses on-board measurement systems to analyze emissions from a diesel engine vehicle during the cold start period. An in-vehicle FTIR (Fourier Transform Inferred) spectrometer and a Horiba on-board measurement system (OBS-1300) were installed on a EURO3 emission-compliant 1.8 TDCi diesel van, in order to measure the emissions. Both regulated and non-regulated emissions were measured, along with an analysis of the NO/NO₂ split. A VBOX GPS system was used to log coordinates and road speed for driving parameters and emission analysis. Thermal couples were installed along the exhaust system to measure the temperatures of exhaust gases during cold start. The real-time fuel consumption was measured. The study also looks at the influence of velocity on emissions of hydrocarbons (HCs) and NOx.

The cold start period of an SI-engine-powered vehicle, was typically around 200 seconds in urban driving conditions. The results of this research show that the cold start period for the diesel engine is shorter than that for the SI engine. Emissions of CO, NO, NO₂, formaldehyde and total hydrocarbons (THCs) were higher during the cold start period than the warmed up period. The magnitude of increase during the cold start was smaller than SI engines. NOx emissions under real-world driving conditions were well above the legislated values. The study of velocity and emissions also found a correlation between emissions of HCs and NO with vehicle velocity, showing a trend of higher speed alongside higher emissions.