There is provided, in one aspect of the present description, an internal combustion engine system. In one example, the system comprises a controller configured to control an intake valve closing timing varying mechanism to vary a closing timing of the intake valve to regulate air charged in a combustion chamber in accordance with engine operating conditions and, in a first engine operating condition where a least volume of air is required to be charged into the combustion chamber, retard a closing timing of the intake valve to a most retarded crank angle which is after bottom dead center during a cylinder cycle and satisfies the following formulas: α≧−0.2685×ε02+10.723×ε0+15.815 and ε0≧11.0, where α is the most retarded crank angle and ε0 is a geometric compression ratio of the engine.