Tuned intake system

Claim 1

An intake system for an internal combustion engine having a plurality of intake tracts (10, 12, 14, 16) of equal length connected in use to extend from individual engine intake ports to a common plenum chamber (18), and a common passage (20) opening into the plenum chamber (18) for supplying air to all the intake ports, wherein the tracts (10, 12, 14, 16) are arranged to open into the plenum chamber (18) in pairs associated with pairs of intake ports, each pair of intake ports having intake valve events which do not overlap with each other, with the ends of each pair of tracts (10, 16, 12, 14) being disposed within the plenum chamber (18) so as to directly face one another, with the tracts being separated by a gap (22) which is narrower than the diameter of the tracts (10, 12, 14, 16), and with the gap (22) being sufficiently wide to permit mass air flow between the respective tracts (10, 12, 14, 16) and the common passage (20) but being sufficiently narrow to couple most of any pressure wave energy emanating from one tract (e.g. 10) directly into the facing tract (e.g. 16).