A uniflow two-stroke engine includes: a cylinder receiving a piston such that the piston can reciprocate therein and defining a combustion chamber above the piston; an exhaust port having one end in communication with an upper end portion of the cylinder; a scavenging port having a scavenging orifice at one end, the scavenging orifice being in communication with a lower part of a side portion of the cylinder such that the scavenging port is selectively brought into communication with and shut off from the combustion chamber by the piston; and an exhaust gas recirculation passage having one end in communication with a part of the side portion of the cylinder above the scavenging port and the other end in communication with the scavenging port such that the exhaust gas recirculation passage is selectively brought into communication with and shut off from the combustion chamber by the piston.

In a cylinder lubrication system for a two-stroke engine, a plurality of lubricating oil supply openings (78) open out in the inner circumferential surface of the cylinder (42) at a point lower than a top ring (22b) of a piston (22) located at a bottom dead center. The lubricating oil supply openings are configured to provide a larger amount of lubricating oil in the thrust side and anti-thrust side of the cylinder than in a remaining part of the cylinder. Thereby, the consumption of lubricating oil and the emission of undesired substances can be minimized while providing an optimum lubrication of the sliding part between the piston and the cylinder.

Disclosed is a piston ported two-stroke compression ignition internal combustion engine comprising: a cylinder having a fixed closed end, and a piston for reciprocation within the cylinder, wherein the closed end of the cylinder and the piston together define a combustion chamber therebetween; at least one heater to heat the combustion chamber; and a controller to control the heater to heat the combustion chamber when the controller determines that a temperature of the combustion chamber has fallen below a threshold temperature during reciprocation of the piston within the cylinder.

A stratified scavenging two-stroke engine includes a first scavenging passage that extends from a first scavenging intake that opens to the inside of the crankcase to a scavenging port that opens to the inside of a cylinder, and a second scavenging passage that branches from the first scavenging passage and extends to a second scavenging intake that opens to the inside of the crankcase. An air passage is provided to supply air for pre-scavenging into the first scavenging passage at a position closer to the first scavenging intake than a position at which the second scavenging passage branches from the first scavenging passage. A first check valve inhibits a flow of air from the first scavenging passage during an upward stroke of the piston, and a second check valve inhibits a flow of air and a gaseous mixture from the first scavenging passage during a downward stroke of the piston.

A uniflow two-stroke engine, includes: a cylinder receiving a piston such that the piston can reciprocate therein; an exhaust port provided in an upper end part of the cylinder; and a scavenging port that is provided in a lower side wall portion of the cylinder so as to be opened and closed by the piston, wherein a downstream portion of the scavenging port that opens out to the cylinder includes a guide member that gives a downward velocity component to a gas flow entering the cylinder from the scavenging port.