Internal combustion engines have been required to improve the thermal efficiency and reduce the pollutant emission, and the previous studies were developed by controlling the air-to-fuel ratio and reducing the pressure fluctuations. For further improvement of the thermal efficiency, it is expected to model the heat transfer phenomena at the intake system and predict the air mass flow rate into the cylinder, which causes to keep the stoichiometric air-to-fuel ratio and improve the fuel consumption. The present study experimentally developed the empirical equation of the heat transfer at the intake system. This was based on Colburn’s equation considering the development of the thermal boundary layer and the unsteady heat transfer phenomena, which was expressed by using the Reynolds, Graetz and Strouhal numbers. Compared with the experimental data and the present empirical equation, the maximum and average errors were estimated within 10.5% and 3.1%, respectively.