The paper describes a combined experimental-theoretical investigation into the intake flow produced by a port commonly used for both DI diesel and gasoline engines, namely a helical.The study consists of two major parts. Firstly, 3 orthogonal velocity components were measured under steady flow conditions within the valve gap using LDA. Data was obtained around the valve periphery and in different planes between the valve and the cylinder head. This was repeated for a number of different valve lifts. Prior to the second stage, an unsteady gas-dynamics calculation was performed to determine the thermodynamic conditions immediately upstream of the valve and the mass flow rate through the valve opening throughout the intake stroke. Finally, the LDA velocity data and the information from the gas-dynamics calculation were combined to provide “quasi-steady” velocity profiles which were used as boundary conditions for a 3-dimensional calculation of the in-cylinder flow during the intake period.The paper describes in detail the experimental and theoretical studies and the results obtained therefrom. The main assumptions, approximations and associated sources of error are discussed. Suggestions are made to improve the understanding of this type of calculation and potential application areas are identified.