PURPOSE: To increase the output and the thermal efficiency of the engine of the type in which alcohol is modified into fuel gas by use of heat possessed by exhaust gas, by providing a fuel supplying means independently of an intake-air passage, and feeding the modified fuel gas directly into a combustion chamber.

CONSTITUTION: A modified fuel gas inlet port 3 is formed at a port of the wall of the combustion chamber of an engine 1, and a modified fuel gas supply valve 4 is disposed at the open end of the port 3 where it is opened in the combustion chamber 2. At an intermediate part of an exhaust-gas passage 6, there is disposed a fuel modifying means 8 incorporating therein an alcohol modifying catalyst and a heat exchanger wall 7 through which heat of exhaust gas is transmitted to alcohol fuel. Here, arrangement is such that liquid alcohol fuel is supplied to the modifying means 8 by a pump 9 and fuel gasified and modified by the means 8 is supplied directly to the combustion chamber 2 via the pipe 5 and valve 4. Further, the modified fuel gas supply valve 4 is controlled to open at a proper timing and for a proper period according to the speed of rotation of the engine 1, load, pressure of the modified fuel gas etc.