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Operating gasoline engines at part load in a so-called Gasoline-HCCI (gHCCI) combustion mode has shown promising results in terms of improved efficiency and reduced emissions. So far, research has primarily been focused on experimental investigations on the test bench, whereas fast, predictive burn rate models for use in process calculation have not been available. Such a phenomenological model is henceforth presented. It describes the current burn rate as the sum of a sequential self-ignition process on the one hand and a laminar-turbulent flame propagation on the other hand. The first mechanism is essentially represented by ignition delay calculation, in which the reaction rate is computed separately for some hundred groups of different temperatures based on the Arrhenius equation. Thermal inhomogeneity is described by a contaminated normal distribution which accounts for the influence of wall temperature on mixture close to the cylinder wall.