In recent years, numerical simulations have become key tool for diesel engine combustion system development due to the requirement of the shorter development duration for the improved performance and better emission levels. In this study, an approach, which integrates numerical and experimental methods in order to characterize the flow field in diesel engine cylinder, is presented. The steady-flow port bench testing, PIV (Particle Image Velocimetry) measurements and numerical simulation methods are used to determine the flow behavior inside the cylinder. Numerical simulation method is validated by using experimental results in terms of mass flow rate and swirl ratio in cylinder. Mass flow rate values predicted within 5 percent error and swirl ratio values predicted within 10 percent error. This proves the viability of numerical method as an important alternative to port bench measurements. In addition to that, cylinder-to-cylinder variation and effects of surface roughness are investigated by swirl ratio measurements and optical diagnostic. Results showed that surface quality and manufacturing problems have significant effects on the swirl ratio in cylinder.