In this work, heat loss was investigated in homogeneous and stratified DI-SI operation mode in a single cylinder research engine. Several thermocouples were adapted to the combustion chamber surfaces. The crank angle resolved temperature oscillations at the cylinder head and piston surface could thereby be measured in homogeneous and stratified operation mode. A grasshopper linkage was designed and adapted to the engine, to transfer the piston signals to the data acquisition device. The design of the experimental apparatus is described briefly.For both operation modes the average steady-state temperatures of the combustion chamber surfaces were compared. The temperature distribution along the individual sensor positions at the cylinder head and piston surface are shown. Furthermore, the curves of the crank angle resolved temperature oscillations in stratified and homogeneous operation mode were compared. It is shown that the local temperature curves show large variations, depending on the operation mode.Using these oscillations, the heat flux profiles were calculated and compared with each other. To calculate the heat flux at the surface of deposits and the deposit thickness, an approach was used, that allows consideration of multiple layers with different material properties and thicknesses.The differences in the heat transfer characteristics are demonstrated for a variation of spark timing in stratified operation mode. For comparison the heat transfer characteristic in homogeneous operation mode is shown at reference spark timing. Finally, the determined heat losses were compared with the predictions of existing models for instantaneous wall heat transfer and rated.