PURPOSE: To increase the torque output by providing a sub-combustion chamber suction valve for opening/closing the conducting section between a gasoline lead port and the sub-combustion chamber and a sub-combustion chamber gate valve for opening/closing the conducting section between the sub-combustion chamber and main combustion chamber.
CONSTITUTION: An internal-combustion engine is provided with a light oil fuel injection nozzle 5 and a suction/exhaust valve 4. A sub-combustion chamber suction valve 10 interlocked with said valve 4 to open/close the conducting section between the gasoline fuel lead port 7 and the sub-combustion chamber 8 is provided. Furthermore a sub-combustion chamber gate valve for opening/closing the conducting section between the sub-combustion chamber 8 and main combustion chamber 2 is provided. When employing the light oil as fuel, it is operated by the converted oil fuel to be injected through an injection nozzle 5. While, when employing gasoline, said nozzle 5 is stopped to open the valves 10, 13 thus to feed gasoline into said chamber 8. Consequently high output is produced to prevent discharge of black smoke.