Abstract: A four-cycle engine wherein a fuel-air-oil mixture is compressed in a crank case chamber and directed therefrom along a pathway to a combustion chamber. The pathway contains actuating mechanism for actuating the fuel intake valve leading to the combustion chamber. The pathway is restricted in volume as permitted by the actuating mechanism, preferable to a range of two to four times the piston displacement.

Abstract: A four-cycle engine wherein a fuel-air-oil mixture is compressed in a crank case chamber and directed therefrom along a pathway to a combustion chamber. The pathway contains actuating mechanism for actuating the fuel intake valve leading to the combustion chamber. The pathway is restricted in volume as permitted by the actuating mechanism, preferable to a range of two to four times the piston displacement.

Abstract: Rotary piston engine having a first intake port formed in rotor housing and one or more second intake ports formed either one or both of the rotor and side housings. The first intake port supplies relatively rich air-fuel mixture having mixing ratio of 2 to 6 and the second intake port supplies air or relatively lean mixture in such a manner that the total air-fuel ratio becomes 15 to 20.

Abstract: Rotary piston engine of fuel injection type wherein fuel injection is performed when the intake air flow is relatively high so that an improved fuel atomization can be attained. Further, the fuel injection timing is also determined from the view point that air-fuel mixture is forced toward the leading part of the intake working chamber. The engine has a peripheral intake port formed in the rotor housing and a side intake port formed in one of the side housings, said side intake port being used only in heavy load range of engine operation. The intake passage leading to the peripheral intake port is inclined in the direction of rotor rotation so that intake fluid is forced toward the leading part of the intake working chamber.

Abstract: Fuel injection type rotary piston engine having side and peripheral intake ports, said side intake port being closed in light load operation and said peripheral port in heavy load operation, said peripheral port having an area which is small in relation to the side port and being closed in each intake stroke after bottom dead center position of the rotor.