: Sources of environmental pollut ion are the motor vehicle consuming t raditional fuels and the industries. About 30% of the total heat generated is  lost in the exhaust gases by an int ernal combustion engine. Under normal  operating condit ions Catalyt ic converters appear to be the most effective means of reducing air pollution from internal  combustion (IC) engines. The conversion efficiency is pract ically zero during the starting and warming -up period. So it  is very important to improve the convers ion efficiency under these condit ions particularly in large cit ies, where the  number of starting per vehicle per day tends to be high. In the present work we tried to enhance the performance of the catalytic converter by maintaining it hot for maximum conversion efficiency. A Phase Change Material [PCM] based  thermal energy storage system integrated with the catalyt ic converter is designed, fabricated and tested. After overnight  stay motorcycle engine is operated during warm up condit ion for half an hour, some of the thermal energy of the  exhaust gases is stored in the PCM during charging period. During engine shut down period (discharging period), PCM underwent partial solidificat ion and the latent heat thus produced is used to maintain the Catalyt ic converter hot for maximum conversion efficiency. Due to this after half an hour when engine is started called as cold start period, it is observed that performance of the catalytic converter is improved.