An internal combustion engine 10 wherein no compression function is carried out in the engine 10 and including a tank 30 of compressed air, a pressure regulator 34, a fuel injector 28, and means 40 and 42 for connecting the pressure regulator 34 and the fuel injector 28 to a foot pedal 38 for controlling air and fuel feed to the combustion chambers 22 in response to throttle demand. The engine can use spark or compression ignition and can provide full expansion. Compressed air can be generated more efficiently using central station power with a vast savings in the amount of oil consumed. The internal combustion engine system of this invention is useful in all applications for such engines including vehicles such as automobiles, trucks, locomotives, marine applications, airplanes, etc. as well as non-vehicle use.