In this study, the computer program was developed to predict the engine performances and exhaust emissions of a 4-cylinder 4-stroke cycle ignition engine including intake and exhaust system. The simulation models applied to each process were as follows. For the combustion process, two zone model which requires only one empirical constant was applied, and for the gas exchange process, the method of characteristics that allows the calculations of the time variation and spatial variation of properties along the pipes was used. Constant pressure perfect mixing model was applied to take into account of the interaction at manifold branches. To predict exhaust emissions, twelve chemical species were considered to be present in combustion products. These species were calculated through equilibrium thermodynamics and kinetic theory. The empirical constants reduced to least number as possible were determined through the comparison with the experimental indicator diagram of one particular operating condition and these constants were applied to other operating conditions. The predicted performances and emissions were compared with the experimental results over the wide range of operating conditions.