| 摘要 |
PROBLEM TO BE SOLVED: To provide an exhaust port cooling device capable of suppressing the lowering of an exhaust gas temperature in an exhaust port at engine start to elevate a catalyst temperature and also of sufficiently cooling the exhaust port after warming up. SOLUTION: During the catalyst temperature is low at engine start, an exhaust side cooling water jacket 6 is separated from a cooling water circulation system by closing the fourth and fifth valves 9 and 10, and such a state that air can be introduced into the jacket 6 is prepared by opening a third valve 19. Further, the water in the jacket 6 is discharged into a discharge water tank 20 by opening a second valve 22 to replace water with air in the jacket 6. When the catalyst temperature is substantially elevated, cooling water is poured into the jacket 6 by closing the second valve 22 and alternatively opening a first valve 17 and then, the first and third valves 17 and 19 are closed in such a state that the jacket 6 is filled with water. Subsequently, the jacket 6 is connected to the cooling water circulation system by opening the fourth and fifth valves 9 and 10.
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