Speed-dependent representative emission factors for catalyst passenger cars and influencing parameters

This paper presents speed-dependent hot emission factors for passenger cars equipped with a three-way catalyst. The emission factors were developed us ing emission data from in-use vehicles based on chassis dynamometer tests c onducted over real-world driving cycles. The variability of the emission da ta and the use of cycles with different characteristics resulted in a low c orrelation between emission factors and mean travelling speed. Analysis of the data identified differences in vehicle emission performance as the main source of variability. The potential for decreasing emission variability b y classifying vehicles according to their engine capacity and mileage was s tudied by means of an analysis of variance test. Results showed that CO, NO x and HC emissions were dependent on mileage but not on engine size. Emissi ons of CO2 were found to be strongly dependent on engine size, but insensit ive to vehicle mileage. (C) 2000 Elsevier Science Ltd. All rights reserved.