INTAKE-AIR DEVICE IN ENGINE

PURPOSE:To aim at enhancing the combustibility of an engine upon low load operation, by providing an auxiliary intake-air passage which is branched off from the bottom of an intake-air passage upstream of a shut-off valve, having a passage area smaller than that of the intake-air passage and is connected either one of plural intake ports. CONSTITUTION:The upstream opening 13a of an auxiliary intake-air passage 13 is opened to the lower wall of an intake-air passage 7 upstream of a shutter valve 12 in the intake-air passage 7, being biased toward a second intake-air port 5 with respect to the center line (l'). The downstream opening 13b of the auxiliary passage 13 is opened at a position which is as near to an intake port 4 as possible, downstream of the branched off point of bifurcated intake-air passages 10, 11. The auxiliary passage 13 is arranged with respect to the branched intake-air passage 10 which is curved with a large curvature axially of an engine cylinder 5 just upstream of the first intake port 4 so that it is directed peripherally of a combustion chamber 2, making a slight angle with respect to the mating surface between a cylinder block and a cylinder head.