Internal combustion engine will remain the major propulsion system for land transportation, for at least the next decade, as the transition to full electrification will not be imminent. Thus, it is important to improve the combustion efficiency and emissions. To achieve this, it is important to understand and control the in - cylinder flow evolution, and primarily the Tumble development as this is strongly connected with the mixing process. Flow field measurements were obtained by using Time Resolved Particle Image Velocimetry technique in a 475cc optical single - cylinder Gasoline Direct Injection (GDI) spark ignition engine. The results include 50 consecutive cycles phase averaged velocity fields at 2000 RPM with wide open throttle. Alongside, Reynolds Averaged Navier Stokes (RANS) simulations were carried out using engine geometry and initial conditions similar with the experiment to compare the flow field and validate quantities such as Turbulent Kinetic Energy (TKE) and Tumble Ratio (TR). Moreover, quantitative comparison conducted by using relevance and magnitude index, and the Γ1 criterion was used to identify the center of vortex structure. It was observed that a tumble like motion with Counterclockwise rotation (CCW) was present when the intake valves were open and continued to evolve at the intake and compression stroke. By comparing the experimental and simulation results, the same trend was observed for TKE and TR, mainly at the compression stroke,. The peak TKE was found at 450 CADs, 2000 RPM, for both TR-PIV and RANS results. The absolute value of TR, which corresponds to vorticity normalized with the angular velocity at the tumble plane, was higher at 450 CADs for the experimental results.