Forced-induction spark-ignition engines for passenger cars have undergone rapid development in just a few years. The development steps towards reducing consumption, improving response and increasing durability have required considerably less time than in the case of the naturally aspirated engine. Forced-induction engines currently employ exhaust gas turbo-charging almost exclusively. By this means the required quantities of air can be supplied with acceptable size, weight and efficiency, together with the advantage of good acoustic characteristics. In step with the combustion engine, the turbo-charger is also undergoing continuous further development.The paper describes the individual development steps, which can be divided into four stages. Particularly good results can be obtained with forced-induction engines incorporating four valves per cylinder.Compared with naturally aspirated engines, forced-induction spark-ignition engines place significantly greater demands on the engine ancillary systems. The higher output levels necessitate the use of inter-cooling, sophisticated ignition and injection systems, heat resistant materials and more efficient cooling, all of which make turbo-charged engines more expensive. The most suitable applications are thus primarily in the performance car category, or for fast touring saloons.