A new method of estimating volumetric efficiency has been developed to facilitate parameter studies necessary for designing a Variable Induction System (VIS). The proposed method is based on the application of frequency domain to solve linearized one-dimensional hydrodynamic equations. This method enabled CPU time to be reduced to 1/200 of that required for non-linear calculation in the time domain.Various VISs having sufficient flexibility to ensure practical uses are introduced. Finally, VISs are classified into four groups depending on the pulsation mode. Two examples of VISs are described and tested. Both are found capable of considerably increasing volumetric efficiency at low and medium engine speeds without loss of maximum power.