A hybrid internal combustion engine and air motor system is provided and includes at least one chamber having a drivable member and at least one intake valve and at least one exhaust valve, and a reservoir connected to the chamber through at least one of the intake valve and the exhaust valve. The system further comprises a computer configured to calculate air compressor efficiency during an air compressor mode of operation and select an intake and exhaust valve opening and closing timing sequence for maximizing air compressor efficiency and/or a computer configured to calculate air motor efficiency during an air motor mode of operation and select an intake and exhaust valve opening and closing timing sequence for maximizing air motor efficiency. A method for selecting an intake and exhaust valve opening and closing timing sequence for maximizing air compressor efficiency and/or for selecting an intake and exhaust valve opening and closing timing sequence for maximizing air motor efficiency is also disclosed.