Patent ID: 8676471

Claim:
A method for determining an index representing a crank angle at which a given fuel mass fraction has been burnt in a cylinder of an engine during an engine cycle, the method comprising the steps of: sampling a pressure within the cylinder during said engine cycle sensed by a pressure sensor; using a processor to: determine the heat release rate curve during said engine cycle with the pressure, determine the heat release rate curve for a cumulative heat release curve during said engine cycle; determine a minimum value and a maximum value of said cumulative heat release curve; calculate a target value of a cumulative heat release between said minimum value and said maximum value using the given fuel mass fraction; identify a goal point of said cumulative heat release curve that corresponds to said target value; assign the crank angle corresponding to said goal point as the index; determine an opening angle within a crank angular range corresponding to compression stroke of said engine cycle; determine a closing angle within the crank angular range corresponding to an expansion stroke of said engine cycle; delimit between a first angular window using said opening angle and said closing angle; and limit said determination of the minimum value and the maximum value of the cumulative heat release curve within said first angular window.