A precise and simplified prediction method of volumetric efficiency and burned gas fraction in the cylinder charge, which are closely related to the power output, emissions, and fuel economy, has been required for the most frequent conditions of city-driving. A fixed volume plenum model for the intake and exhaust manifold was used as an analytical model of the gas exchange process, because of the very small effects of pulsation under these conditions. The application limit and the close examination of this model were investigated by experiments and calculations on the volumetric efficiency and burned gas fractions in the cylinder charge. Furthermore the IMEP, ISNO, ISFC were predicted for the changes in the valve timings. As a result, it was clarified that a wide range of operating conditions would fall within the limits of this prediction model, and this model was valid in predicting the gas exchange process under city-driving conditions.