To suppress disagreeable noises attributable to the difference in frequency of the pressure pulsation caused by the difference in passage length by setting the passage length from a throttle valve to a suction passage to be substantially equal to each other while miniaturizing an air intake device.
The length L2 between both ends 15a and 18a in the direction of the cylinder bank in second upstream end opening parts 15a-18a is set to be shorter than the length L3 between both ends in the direction of the cylinder bank in intake ports 8 opened in one side part of an engine unit 2 and arranged continuous in the direction. The length L1 between both ends 11a and 14a and 12a and 13a in the direction of the cylinder bank in first upstream opening parts 11a-14a is set to be shorter than the length L2 between both ends 15a and 18a in the direction of the cylinder bank in the second upstream opening parts 15a-18a. The first upstream end opening parts 11a, 12a and 13a and 14a partially overlapping each other are arranged substantially on the same circumference with respect to the second upstream end opening parts 16a and 17a located in the middle with respect to the direction of the cylinder bank.
HIRASHITA SHIGEYUKI
FUJIKAWA TATSUYA
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