A powertrain includes an Atkinson cycle engine having at least one cylinder, a crankshaft, and an air intake system that provides selective fluid communication between the at least one cylinder and the atmosphere. A motor is in hybrid combination with the engine, and a compressor is configured to selectively pressurize air in the air intake system. The powertrain provides the fuel efficiency of an Atkinson cycle engine while compensating for the reduced torque output of an Atkinson cycle engine.