Due to future directives of the European Union regarding fuel consumption and CO2 emissions the automotive industry is forced to develop new and unconventional technologies. These include for example stop-start-systems, cylinder deactivation or even reduction of the number of cylinders which however lead to unusual acoustical perceptions and customer complaints.Therefore, it is necessary to evaluate the sound character of engines with low numbers of cylinders (2 and 3 cylinders) and also the differences to the character of the more common 4-cylinder engines. Psychoacoustic parameters are used to describe and understand the differences. Based on the gained knowledge possible potentials for improvement can be derived in the future.The used data base consists of artificial head recordings of car interior noise according to defined driving conditions measured on the AVL test track. Naturally, there are more recordings available for 4-cylinder engines than for 2- and 3-cylinder engines. This has to be taken into account in the statistical evaluations.Using the most representative vehicles and driving conditions in the data base the sounds of engines with different numbers of cylinders should be objectively characterized.The aim is to use psychoacoustic parameters to separate the different engine groups and to describe how much they differ. In the end, the gained knowledge about the parameters should help to adapt the sound character to that of 4-cylinder engines to make the 2- and 3-cylinder sound more usual and comfortable.