Patent ID: 6860252

Claim:
A combustion system for a four-stroke internal combustion engine having at least one cylinder and a piston which reciprocates therein, comprising: two substantially identically sized poppet type intake valves actuated in unison to thereby admit combustion air into the one cylinder, a cylinder head portion for (a) closing an end of the one cylinder, (b) guiding a stem portion of each of said two intake valves in a direction of valve opening and closing travel substantially parallel to the direction of the geometric axis of the one cylinder and (c) supporting an individual seating surface for a head portion of each of said two intake valves to seal against in a closed position which maintains gaseous pressure on the piston during compression and power strokes of the piston in the one cylinder, said two intake valve seats being located substantially adjacent each other in said cylinder head, an individual passage for supplying combustion air to each of said two intake valves, the combination of one of said intake valves and its associated one of said intake passages being substantially mirror-image symmetric with a combination of the other of said intake valves and the other of said intake passages, said symmetry being with respect to a plane which passes through the geometric axis of the one engine cylinder, each of said two valve head portions having an outer circumference which overlaps area outside the circumference of the bore of the one cylinder when all three of said circumferences are generated as projections onto a plane normal to the geometric axis of the one cylinder, said overlapping area of each of said intake valve heads being less than half of its total circumference area, whereby each of said two intake valves opens into a combustion chamber formed at said closed end of the one cylinder, and for each of said two intake valves an individual relief volume contained in said combustion chamber to accommodate said overlapping valve head area when in a fully open position, each of said two relief volumes being contoured to comprise at least a portion of a flow mask shrouding its respective one of said intake valves, said two masks together functioning in conjunction with simultaneous opening of said two intake valves to direct combustion air-generally across the bore of the one cylinder from said valves and parallel to said plane of symmetry to thereby generate barrel swirl in two symmetric layers of combustion air, one supplied from each of said two intake passages during an intake stroke of the piston, whereby said relief volumes of said combustion chamber allow location of said head portions of said two intake valves in positions which liberate space in said combustion chamber directly over the bore area of the one cylinder.