Intake system of an internal combustion engine

Claim 1

An internal combustion engine comprising a cylinder head partially defining a combustion chamber, said cylinder head comprising at least one helically-shaped intake port to direct intake gas to said chamber, said intake port comprising a helical portion having an open outlet end and an intake valve arranged at said outlet end, said helical portion being defined by an upper wall and a peripheral side wall which extends circumferentially about the axis of said intake valve, and a substantially straight inlet passage portion tangentially connected to said helical portion and having an open inlet end, said inlet passage portion being defined by an upper extension of said upper wall, a bottom wall, a first side wall located near the axis of said intake valve, and a second side wall arranged at a position more remote from the axis of said intake valve than the first side wall and connected to the peripheral side wall of said helical portion, said first side wall comprising a portion sloped inwardly toward said second side wall, said side wall increasing in width toward said helical portion and intersecting said upper wall closer to said second side wall in a region closer to said helical portion than in a region closer to said inlet end to reduce the cross-sectional size of the inlet passage portion adjacent to said helical portion and to deflect at least part of said gas toward said combustion chamber; and an intake manifold comprising a manifold inlet portion and a substantially straight manifold outlet portion connected to, and in line with, the inlet end of said inlet passage portion, the ratio of the sum of the length of said inlet passage portion and the length of said manifold outlet portion to the cross-sectional area of said inlet end being above 0.7 cm -1 .