In order to analyze intake port flow characteristics of a four-valve direct injection (DI) diesel engine, steady-state flow bench experiments and numerical simulations method were coupled to investigate the following four combined intake ports: (1) helical port (left) and tangential port (right); (2) tangential port (left) and helical port (right); (3) helical port (left) port and helical (right); and (4) tangential port (left) and tangential (right) port. Results show that the simulation of port flow coefficients matches experimental findings very well, and the port coefficients of the above four combinations do not vary much, but their swirl ratios are very different. Specifically, when the valve lift is the maximum, the swirl ratio of the combination of "helical and tangential" is the greatest among the four combinations, and the swirl ratio of "tangential and tangential" is the minimum. And the3D fluid simulation method and steady-state experiment are important means to investigate the flow characteristics of the combined intake ports
