The present invention relates to an internal combustion engine and, more particularly, an internal combustion engine having a new and novel system for improving the efficiency of the engine. In a preferred embodiment the system comprises an expander effective for receiving condensed engine exhaust and placing said exhaust in contact with copper or a copper alloy and for transforming the exhaust into vapor for transfer into the combustion chamber of the engine. In a preferred embodiment the system further comprises a condenser means for cooling the exhaust exiting the engine sufficiently to condense any water vapor and/or fuel vapor to form a liquid mixture or water and fuel, collecting and storing the liquid mixture, and directing the stored liquid mixture to the expander.