Abstract: A piston has formed in the top thereof a part-spherical depression which forms part of a combustion chamber. The depression is so formed as to permit the flame front during the initial stage of combustion to reach the surface of the depression substantially at the same time, giving better conditions for efficient combustion and short combustion duration.

Abstract: A split engine is disclosed which includes first and second groups of cylinders and an intake passage having its downstream portion divided into first and second branches leading respectively to the first and second groups of cylinders. At low load conditions, the second intake passage branch is disconnected from the intake passage and supplied with exhaust gases. A passage is provided which has its one end opening into the crankcase and the other end opening into the first intake passage branch for introducing blow-by gases into the first intake passage branch.

Abstract: An engine is equipped with a fuel injector in an intake passageway immediately upstream of an intake valve. Air introduced from the intake passageway upstream of a throttle valve is ejected toward a clearance between the valve head of the intake valve and a valve seat, when the intake valve is opened. The ejected air stream strikes against the sprayed fuel injected from the fuel injector to improve the atomization of injected fuel and to form homogeneous air-fuel mixture to be inducted into the combustion chamber of the engine.

Abstract: An engine is equipped with a fuel injector in an intake passageway immediately upstream of an intake valve. Air introduced from the intake passageway upstream of a throttle valve is ejected toward a clearance between the valve head of the intake valve and a valve seat, when the intake valve is opened. The ejected air stream strikes against the sprayed fuel injected from the fuel injector to improve the atomization of injected fuel and to form homogeneous air-fuel mixture to be inducted into the combustion chamber of the engine.

Abstract: An internal combustion engine is disclosed which comprises a plurality of cylinders split into first and second groups, means responsive to engine low load conditions for cutting off flow of fuel and fresh air to the second group of cylinders, an exhaust passage provided at its downstream end with a catalyzer, a partition extending through the exhaust passage to the vicinity of the catalyzer to divide the exhaust passage into two passages, one connecting with the first group of cylinders, the other connecting with the second group of cylinders, an EGR passage bypassing the second group of cylinders for exhaust gas recirculation, and an EGR valve provided in the EGR passage and adapted to open the same in response to engine low load conditions.

Abstract: An auxiliary passage of a relatively small cross-sectional area bypasses the main throttle valve of a usual induction passage to extend to each intake port. The auxiliary passage allows air or an air-fuel mixture to pass therethrough according to the magnitude of vacuum in the intake port and, in its endmost portion, takes the form of a nozzle directioned circumferentially of the intake port, so that the air-fuel mixture flowing in the intake port is agitated to thorough homogenization by a swirling movement of the injected gas particularly efficiently during low load operation of the engine.

Abstract: An auxiliary intake passageway and an auxiliary intake valve operated for allowing an excessive air-fuel mixture to be drawn into a combustion chamber of an engine through the auxiliary intake passageway and for expelling the drawn excessive air-fuel mixture from the combustion chamber during low load operations of the engine and a bypass intake passageway and an auxiliary valve or a throttle valve operating device for increasing the flow of air passing through the intake passageway of the engine during the engine low load operations for ensuring the excessive air-fuel mixture drawn into the combustion chamber.

Abstract: The disclosure concerns an internal combustion spark ignition engine including a cylinder; a reciprocating piston in said cylinder and defining a combustion chamber therewith; dividing means for dividing the combustion chamber into a main and an auxiliary section, said auxiliary section being in communication with only the main section, an orifice in said dividing means for connecting the said sections, the volumes of the main and auxiliary sections and the size of the orifice being selected to be such that, during a compression cycle, part of the combustible mixture of air and fuel enters into the auxiliary section in such a manner as to cause great turbulence therein, and a spark plug provided in the auxiliary section for causing ignition.