In this study, as a means of increasing engine power, turbocharging was applied to the gasoline engine of a light passenger car which was originally naturally aspirated. Also the catalytic convertor was applied to improve the exhaust emission characteristics. The comparison of the performance characteristics between the burbocharged engine with catalytic convertor and the naturally aspirated engine was made over the wide range of operating conditions. The results showed considerable increase of the output performances at full load condition by trubocharging while slight losses were observed at part load conditions.