METHOD FOR DETERMINING AN INDEX OF THE FUEL COMBUSTION IN AN ENGINE CYLINDER

A method is provided for determining an index representing the crank angle at which a given fuel mass fraction has been burnt in a cylinder of the engine during an engine cycle. The method includes, but is not limited to sampling the pressure within the cylinder during the engine cycle, using the pressure samples for determining the heat release rate curve during the engine cycle, using the heat release rate curve for determining the cumulative heat release curve during the engine cycle, determining a minimum value and a maximum value of thee cumulative heat release curve, using the given fuel mass fraction for calculating a target value of the cumulative heat release between the minimum and maximum values, finding a goal point of the cumulative heat release curve that corresponds to the target value, assuming the crank angle corresponding to the goal point as the index. The method further includes, but is not limited to determining an opening angle within the crank angular range corresponding to compression stroke of the engine cycle, determining a closing angle within the crank angular range corresponding to the expansion stroke of the engine cycle, using the opening and closing angles for delimiting between them a first angular window, and limiting the determination of the minimum and maximum values of the cumulative heat release curve within the first angular window.