This study is based on experimental test results, typical for small passenger car diesel engines. The influence of engine size on the performance of the car was investigated using four different types of engine. The four types of engine were (a) naturally aspirated engine, (b) engine with turbocharger and waste gate, (c) engine with pressure wave supercharger (PWS) and (d) engine with PWS and intercooler. The performance of the car fitted with the pressure wave supercharger Comprex R* was examined and found to have excellent response, reduced fuel consumption and reduced exhaust emissions.