Three dimensional flow calculations of the operation cycle of a small 4-stroke variable compression spark-ignited engine have been performed for different engine speeds under full load conditions. The compression ratio at the laboratory engine is adjusted within the range of 4 to 10, by means of a special piston, which moves manually and alters accordingly the combustion chamber volume. Calculations were performed for three different engine speeds and two compression ratios. Ensemble-averaged velocity data are presented in two main forms: velocity magnitude at characteristic points as a function of crank angle and twodimensional vector plots at characteristic cross sections inside the combustion chamber at specific crank angles. The results confirm that the in-cylinder flow field scales well with the engine speed and that increasing the compression ratio results in more pronounced large scale flow-field effects, such as the tumbling motion generated during the induction stroke and persisting through the compression stroke.