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This paper presents heat release regressions for the combustion modes in a gasoline direct injected (GDI) engines. These heat release regressions can be used in one-dimensional flow codes and mean value models as a simplified representation of combustion. The heat release profiles are approximated as functions of crank angle, with some free parameters. These parameters are fitted as functions of engine operating conditions, so that a continuous family of curves is obtained. GDI engines have four distinct modes of combustion: homogeneous rich, homogeneous stoichiometric, homogeneous lean and stratified lean, each requiring its own functional approximation. We present the functional approximations, the dependence of the parameters on engine operating conditions, and the quality of the fit on data from a 1.8 liter production GDI engine.