| 摘要 |
PURPOSE:To secure high output in a wide operation range, by specifying a ratio in a passage sectional area of a carburetor primary system Venturi part in relation to a minimum passage sectional area nearby a suction valve of a suction port for low load use, in case of a two-system type suction system carrying a diaphragm type multi-barrel carburetor. CONSTITUTION:A multi-barrel carburetor 7 interconnects its primary system 8 to a suction port 4 for low load use via a first suction pipe 9 as well as interconnects a secondary system 11 to a suction port 5 for high load use via a second suction pipe 12. In this case, a ratio in an effective passage sectional area S2 of a Venturi part 13 of the carburetor primary system 8 in relation to a minimum passage sectional area S1 at a proximity part 4a of the low load suction port 4 is set to a value in the range of 0.9-1.1. With this constitution, an opening characteristic in a throttle valve 17 of the secondary system 11 to be demanded in view of output can be maintained as specified, while suction resistance in the primary system 8 is able to be held down to a relatively small value so that high output in a wide operation range can be secured. |
