Abstract: According to one implementation of an engine system, a power device is selectively actuated to provide energy to a storage device. Energy from the storage device is selectively provided to a boost assist device to supplement the normal energy supply to a boost device and enable an increased power output of the engine in at least certain engine or vehicle operating conditions. In one form, the power device may be a source of electrical energy and the storage device is capable of storing an electrical charge. In another form, the power device is a fluid pump and the storage device is capable of storing pressurized fluid. Various methods may be employed to control operation of the power device and energy storage in the storage device.