Abstract: An engine management system for an internal combustion engine, which has at least one cylinder pressure sensor and at least one engine actuator, includes a data processor arranged to receive and process cylinder pressure data from the cylinder pressure sensor and the actuator controller arranged to control the actuator to optimize engine performance based on the processed data, in which the cylinder pressure data is obtained during a performance optimized engine cycle or cycles. The processor processes the data to construct a cylinder pressure variation function for the engine cycle or cycles and derive control data therefrom for the actuator controller.