An exhaust-gas turbocharging, compression increases the temperature of the fresh air in the charger. Since heated air occupies a larger space than cool air, the cylinders fill with less air than would correspond to the boost pressure and in petrol engines the tendency to knock increases. For this reason, the compressed air is cooled by the engine's cooling water or the outside air. Intercooling reduces the thermal stress on the engine. In addition, the exhaust gas temperature, NOx emissions and fuel consumption are reduced.