Abstract: In an induction system for an internal combustion engine having two groups of cylinders of which firing orders are respectively discontinuous, a groove is formed in a joining end face of a collector unit to be joined with a joining end face of an intake manifold in such a manner as to have a straight main groove section disposed between first and second groups of outlet ports so as to be equidistant from the outlet ports and a plurality of outlet groove sections branching off from the main groove section to fluidly connect the main groove section to each outlet ports. When the joining end faces of the collector unit and the intake manifold are joined together, a fluid recirculation passage such as a blow-by gas recirculation passage, an exhaust gas recirculation passage or the like is defined therebetween.

Abstract: An air intake passage leads to a combustion chamber. A throttle valve is disposed in the air intake passage. A first gas passage connects a crank chamber to a point of the air intake passage downstream of the throttle valve. A control valve is disposed in the first gas passage. A second gas passage connects the crank chamber to a point of the air intake passage upstream of the throttle valve. A communication passage connects the second gas passage to a point of the first gas passage between the control valve and the crank chamber.

Abstract: In an induction system having two independent air supply lines for supplying air to two groups of engine cylinders of which firing orders are respectively discontinuous, an additional air supply passage bypassing throttle valves of the respective air supply lines has a bifurcated downstream end fluidly connected to the air supply lines.

Abstract: An intake and exhaust manifold arrangement of a multiple-cylinder internal combustion engine, comprising an intake manifold including branch portions leading to the intake ports and mounting flange members securely connecting the branch portions to the cylinder head, an exhaust manifold including branch portions leading from the exhaust ports and mounting flange members securely connecting the branch portions to the cylinder head, the branch portions of the exhaust manifold including at least one branch portion adjacent one of the branch portions of the intake manifold, and mounting bolts including at least one common mounting bolt securing the adjacent two branch portions of the intake and exhaust manifolds to the cylinder head, the one bolt and the two flange members having clearances provided therebetween in directions parallel with the direction in which the engine power cylinders are arranged in series, the adjacent two flange members being spaced apart from each other in a direction parallel with the af