A method of achieving a desired torque output of an internal combustion engine includes determining a first air-per-cylinder (APC) value based on a first APC relationship and determining a second APC value based on a second APC relationship. An APC error is determined based on the second APC value. Operation of the engine is regulated based on the first APC value when the APC error is greater than a threshold error. Operation of the engine based on the second APC value when the APC error is not greater than the threshold error.