In order to achieve the strict emission regulations, it is needed to improve the performance of the three way catalyst. Perturbation is the exhaust gas control method to improve CO, NO and Total hydrocarbon (THC) conversion rates by switching the excess air ratio between rich phase and lean phase. In this research, 4-cylinder gasoline engine tests were conducted, and the relationship between the exhaust gas temperature and conversion rates are analyzed. Engine rotation speed was 4000 rpm and specific volume was 1.4×105 h-1. Additionally, the adsorption amount of CO, NO and THC, and the oxygen storage capacity of the catalyst are calculated. From the results, the conversion rate of THC is hardly affected by the perturbation and the exhaust gas temperature. On the contrary, conversion rates of CO and NO are improved by the perturbation. At high temperature, conversion rates and adsorption amount of CO and NO are increased. The variation of oxygen storage capacity of the catalyst is also improved at high temperature.
Morimoto et al. (Wed,) studied this question.