EVOLUTION OF POLLUTANT EMISSIONS FROM PASSENGER CARS DURING COLD STARTS

Evolution of pollutant emissions from passenger cars under cold start conditions. CO, CO2, HC, CH4, NOx and N2O emissions were measured on ten conventional petrol-engined passenger cars, ten vehicles equipped with a three-way catalyst, and five diesel-engined vehicles over a great number of driving cycles under hot or cold start conditions: two standardized European and American cycles, four hot cycles representative of real-world driving conditions, and three representative mini-cycles, which were repeated 15 times after a cold-start. Simultaneously, water and oil temperatures were measured to assess engine temperatures. The analysis of the results enabled the follow up of emission and temperature changes with time for various kinematic types. The limit of hot temperature, the duration of cold-start emissions (over about 6 km) and excess emission rates under cold start conditions could be thus determined. These parameters significantly vary a lot according to vehicle technology, driving behaviour and pollutant type. These results should allow an accurate modeling of excess emissions under cold start conditions.