The GDI process leads to combustion with lean mixtures which may lead to improved fuel economy and emissions relative to homogeneous spark ignition ( SI) engines. To satisfy the different steps of operation, the tuning of GDI engines requires a model with a very short computation times to simulate the engines in the whole operating range and to reduce the number of engine tests which are time consuming and very expensive. Therefore the objective of this paper is to present a reduced model to analyze the combustion process in GDI engines, applied to a homogeneous stoichiometric mode. The objective of the model is to reproduce the same tendencies as those obtained by 3D models, but with a reduced computational time. The 1D model is obtained thanks to a reduction methodology based on the geometry of the combustion front computed with 3D models of the KIVA-II type. The results of the 1D model are compared to those obtained by the KIVA IIGSM under different engine conditions and to the measured pressure. The comparison shows that the 1D model overestimates the maximum cylinder pressure, which has an insignificant effect on the net indicated work per cycle. The results obtained by the 1D model are close to those given by the 3D model, with a much reduced computation time.