Method and apparatus for optimizing the operation characteristics of an engine

An engine control method and apparatus for optimizing an operating condition of an engine. A plurality of engine variables are determined and operated upon to direct the control of engine effectors so as to place the engine in an optimum operating condition. In particular, the engine effectors are controlled to minimize the fuel consumption of an engine operating at a steady-state. The system selectively moves a pair of engine effectors so as to determine the sensitivity of the engine variables to changes in effector outputs. Such sensitivities are updated during the system operation. The engine effectors are selectively moved as a function of the engine variable sensitivities in a direction to minimize fuel consumption without violating any predetermined operating limits of the engine variables. Once an optimum operating point is obtained, the system remains at rest and checks for changes in operating conditions that may require a new optimum to be determined.