Analysis of CO and NOx deviations under on-road driving test of gasoline vehicle with three-way catalyst

RDE has recently been adopted in emission tests in order to measure exhaust gases under actual driving conditions. However, difference in driving routes and traffic conditions would cause deviations in the emission results. A correction factor is applied to compensate for the deviations, but it does not work properly. Thus, CO and NOx deviations were analyzed in the present study. Ten cases of on-road driving were conducted on three driving routes. CO emissions were highly dependent on the coolant temperature and equivalence ratio. About 10 % of CO was exhausted during the cold start, and the rich air-fuel mixture increased the CO emissions by more than two times. NOx emission was also strongly affected by the equivalence ratio and catalyst temperature. About 15 % of NOx was exhausted when the catalyst temperature was low. Oxygen saturation of the catalyst and high load condition were also the reasons for the NOx deviation.