| 摘要 |
PURPOSE:To suppress the occurrence of knocking and reduce a fuel consumption, by a method wherein depressed lengths of valve sheet rings located to ports away from and in the vicinity of an ignition plug are set to a specified relation. CONSTITUTION:An internal-combustion engine has a main suction port 11, an auxiliary suction port 12, an exhaust port, etc. The depressed length l1 of the valve sheet ring 19 of the auxiliary suction port 12 located to a squash area 8a part positioned away from an ignition plug 14 and having a large area is set to a value being longer than the depressed length l2 of a valve sheet ring 18 of the port 11 located to a position nearer to the ignition plug 14. The auxiliary suction port 12, formed in the squash area 8a where end gas is susceptible to occur, has a smaller diameter compared with that of the main suction port 11. This enables suppressing of a rise in temperature of a wall surface to a narrow range, which results in suppressing the occurrence of knocking and reducing fuel consumption. |
