Representativity of Exhaust Pollutant Concentrations for Measuring Pollutant Emissions from Passenger Cars

Exhaust concentration (in ppm) and emission (in g/km) measurements (for CO, HC, NOx and CO2) will be compared over a sample of 49 as-received gasoline engined vehicles, in which 10 were equipped with a 3-way catalyst, in order to assess the viability of rapid methods of emission measurements. The exhaust gas concentrations at the tailpipe were measured from 15 engine operating conditions (6 engine speeds, 4 gear choice). The emission measurements were performed using European standardized cycles ECE15 and ECE15+EUDC and 4 specific actual cycles, representative of the various vehicle usages.

The results obtained are not encouraging as regards the interest of concentration measurements at the tailpipe, even with optimum engine operating conditions: the relationship between exhaust concentrations and actual or standardized emissions is always very poor. The best correlation depends on the pollutant, but could be for 3000 rpm in neutral. In addition, different emission factors will be presented and analysed.