Abstract: Disclosed is a two cycle engine designed and configured to replace conventional four cycle engines in a modern day automobile without any alternations, while steel accepting all of the accessories (i.e. air conditioning, power steering, alternators), without any modifications to the external structure of the engine block. This engine composites casting carbon--carbon cylinders, having carbon--carbon pistons located therein, into an aluminum block so all of the current external dimensions are maintained for manufacturing purposes.

Abstract: An internal combustion engine is provided with an air compressor that receives precharged air from the crankcase of the engine. By providing pressurized air to the air compressor, the mass flow through the compressor can be increased without requiring an increase in the size of the compressor. The plurality of crankcase chambers of the engine can be connected to a common manifold chamber which, in turn, can be connected to the air inlet of the compressor. The air outlet of the compressor can be connected to a plenum chamber that is, in turn, connected to all of the fuel injectors of a fuel injected engine. Alternatively, the air outlet of the compressor can be used to provide pressurized air to other portions of the engine, whether it is fuel injected or carbureted.

Abstract: A low emission power generating apparatus which comprises a modified two-stroke diesel engine component and a modified turbocharger component which has a relatively low aspect ratio. The diesel engine component is a modification of a conventional two-stroke diesel engine design and includes an exhaust valve cam of unique design that has a cam profile which results in a later than-normal exhaust valve opening and an earlier-than-normal valve closing so that the time during which the exhaust valve remains open is shorter than normal, thereby causing a substantially greater volume of residual gases to remain in the combustion chamber following the scavenge stroke. This increase in the volume of the residual exhaust gases within the chamber leads to an increase in compression temperature and effectively increases the compression ratio and consequently the compression pressure.

Abstract: A low emission power generating apparatus which comprises a modified two-stroke diesel engine component and a modified turbocharger component which has a relatively low aspect ratio. The diesel engine component is a modification of a conventional two-stroke diesel engine design and includes a modified connecting rod assembly which causes a modified piston to accelerate rapidly within the combustion chamber and an exhaust valve cam of unique design that has a cam profile which results in a later than-normal exhaust valve opening and an earlier-than-normal valve closing so that the time during which the exhaust valve remains open is shorter than normal, thereby causing a substantially greater volume of residual gases to remain in the combustion chamber following the scavenge stroke. This increase in the volume of the residual exhaust gases within the chamber leads to an increase in compression temperature and effectively increases the compression ratio and consequently the compression pressure.

Abstract: In constructing a suction device for a crank chamber supercharged engine 1 wherein intake air pressurized by a supercharge mechanism is supplied to a combustion chamber, it is arranged that the supercharge mechanism and the combustion chamber are communicatively interconnected by suction passage 38, 46, with an intake valve 7 disposed open/close operably at a downstream end of the suction passage 46, the intake valve 7 being adapted to close between 70 and 100 degrees after a bottom dead center.

Abstract: A hand-guided working tool has a housing and an internal combustion engine arranged in the housing. The internal combustion engine has a cylinder, a crankshaft, and a crankcase enclosing the crankshaft. An air filter box including an air filter element is connected to the internal combustion engine. A tool is driven by the crankshaft. The housing has a blower chamber with a cooling air inlet, at least one combustion air inlet, and a combustion air outlet. A combustion air channel connects the combustion air outlet to the air filter box. A blower, driven by the crank shaft and arranged in the blower chamber, is provided for taking in cooling air through the cooling air inlet and supplying the cooling air to the internal combustion engine and for taking in combustion air through the at least one combustion air inlet and guiding the combustion air through the combustion air outlet, the combustion air channel, and the air filter box to the internal combustion engine.

Abstract: A method of operating a two-cycle internal combustion engine under low load conditions. A throttle is placed at the intake air system to reduce air intake into the engine cylinders. A pump is placed in the exhaust system, such that it creates reduced pressure downstream of the exhaust valves. In this manner, when the air intake ports close, the exhaust is evacuated and the air trapped in the cylinder is reduced. This permits fuel to be reduced so that the engine may operate in a low load state without losing combustion.

Abstract: The modification of the exhaust valve of a two cycle diesel engine in order to increase the amount of the valve stem travel and hence larger annular opening, without changing the total time period or degrees of crank shaft rotation during which time the exhaust valve is open and permits the combusted fuel air mixture to exhaust is disclosed. In cooperation with the improved valve opening, the intake port for the intake air is lowered and lengthened to therefore permit a longer power stroke, and the input of more air which, when combined with the improved scavenging, increases the amount of oxygen available for combustion. The increase in the opening of the valve is achieved by shortening one of the two arms of the rocker arm which engages the valve stem, the arm shortened being the arm which is activated by the push rod. This results in a lengthening of the stroke of the valve stem and the valve which translates into a larger annular opening for exhaust. In addition, the exhaust sector of the 180.degree.

Abstract: A two-cycle engine for boosting intake pressure for higher performance per displacement. The two-cycle engine includes a crankcase having a blower housing and a crankshaft therein extending through the blower housing. The blower housing has an intake opening and a discharge opening. An impeller is disposed around the crankshaft. At least one cylinder is provided with a corresponding piston therein. The cylinder has an exhaust port located on a side wall of the cylinder. An intake conduit extends along the side wall of the cylinder in a spiral rising towards the top of the cylinder and passing beneath the exhaust port to terminate at a pair of intake ports in the side wall of the cylinder. A boost plenum has an intake tube fluidly connecting the discharge opening of the blower housing to the boost plenum. The boost plenum also has a discharge tube fluidly connecting the boost plenum to the intake conduit.

Abstract: A low emission power generating apparatus which comprises a modified two-stroke diesel engine component and a modified turbocharger component which has a relatively low aspect ratio. The diesel engine component is a modification of a conventional two-stroke diesel engine design and includes an exhaust valve cam of unique design that has a cam profile which results in a later-than-normal exhaust valve opening and an earlier-than-normal valve closing so that the time during which the exhaust valve remains open is shorter than normal, thereby causing a substantially greater volume of residual gases to remain in the combustion chamber following the scavenge stroke. This increase in the volume of the residual exhaust gases within the chamber leads to an increase in compression temperature and effectively increases the compression ratio and consequently the compression pressure.

Abstract: An improved two stroke cycle engine is disclosed. The engine has an intake port for passing air into a cylinder of the engine and has a piston within the cylinder for reciprocal movement between a top dead center position and a bottom dead center position. The engine includes a crankcase, an intake valve in a wall of the crankcase, a plenum chamber for supplying air to the intake port and an output valve positioned between the crankcase and the plenum chamber. The engine also includes an air compressor and an air compressor valve positioned between the air compressor and the plenum chamber. The engine has a first mode of operation during startup wherein the piston draws air into the crankcase through the intake valve and then forces air from the crankcase, through the output valve, into the plenum chamber and to the intake port.

Abstract: A method wherein a number of cylinders (2, 3; 1, 4) are grouped on a same exhaust gas manifold (8, 10) such that the pressure in the exhaust pipe (1e . . . 4e) undergoes time-dependent fluctuations of substantial amplitudes, and the exhaust valve (6) of a cylinder (1) is opened during induction or filling thereof (i.e. adjacent to the bottom dead center) so that, in a given engine speed range, a phase (28) of low instantaneous exhaust pressure prevailing in the exhaust pipe enables the inlet pipe (1a)/cylinder (1)/exhaust pipe (1e) to be scavenged while the inlet valve (5) and the exhaust valve (6) are simultaneously open. The phase (29) of high instantaneous exhaust pressure, caused by another cylinder, after the inlet valve (5) has closed and while the exhaust valve (6) is still open, is used for post-charging the cylinder (1) with air (A) previously stored in the exhaust pipe (1e).

Abstract: A method of controlling the air supply to a scavenged internal combustion engine having a blower for suppling air thereto and bypass means for allowing a bypass air flow from the outlet side of the blower to the inlet side thereof, the method including regulating the bypass air flow through the bypass means to provide a variable rate of air flow therethrough and regulating the flow of ambient air to the blower to thereby control the pressure of the intake air supply to the blower and controlling a supply of recirculated exhaust gas introduced upstream of the blower by controlling the flow rate of ambient air to the blower such that a requisite pressure is generated upstream of the blower to thereby control the exhaust gas flow rate.

Abstract: A low emission power generating apparatus which comprises a modified two-stroke diesel engine component and a modified turbocharger component which has a relatively low aspect ratio. The diesel engine component is a modification of a conventional two-stroke diesel engine design and includes an exhaust valve cam of unique design that has a cam profile which results in a later-than-normal exhaust valve opening and an earlier-than-normal valve closing so that the time during which the exhaust valve remains open is shorter than normal, thereby causing a substantially greater volume of residual gases to remain in the combustion chamber following the scavenge stroke. Reduction in peak combustion temperature advantageously results in the lower than normal production of nitrogen oxide (NOx) and, therefore, allows advancement of the injection timing, while still maintaining the NOx emissions coming from the engine lower than those legislatively mandated.

Abstract: An internal combustion engine of either two-cycle or four-cycle construction including a block having at least one cylinder bore therein having sidewalls carrying a liner of a structural fiber reinforced ceramic matrix composite material disposed in sealed fiber reinforced sliding relationship within the cylinder bore, and a cylinder head sealing atop end of the cylinder bore to form a closed combustion chamber in combination with the piston. The cylinder head also has the structural fiber reinforced ceramic matrix composite material disposed on an inner surface thereof facing the combustion chamber. The preferred engine is a two-cycle engine having an externally scavenged intake system and an oil sump lubricating system thereby eliminating the need to separately mix or inject lubricating oil. Higher operating temperatures and closer tolerances allow higher fuel efficiency and less pollutant production.

Abstract: The modification of the exhaust valve of a two cycle diesel engine in order to increase the amount of the valve stem travel and hence larger annular opening, without changing the total time period or degrees of crank shaft rotation during which time the exhaust valve is open and permits the combusted fuel air mixture to exhaust is disclosed. In cooperation with the improved valve opening, the intake port for the intake air is lowered and lengthened to therefore permit a longer power stroke, and the input of more air which, when combined with the improved scavenging, increases the amount of oxygen available for combustion. The increase in the opening of the valve is achieved by shortening one of the two arms of the rocker arm which engages the valve stem, the arm shortened being the arm which is activated by the push rod. This results in a lengthening of the stroke of the valve stem and the valve which translates into a larger annular opening for exhaust. In addition, the exhaust sector of the 180.degree.

Abstract: A multi-cylinder two-stroke cycle engine according to the invention incorporates a plurality of cylinders (1,2,3) arranged in line with each cylinder having at least two inlet ports one on each of the two opposite longitudinal sides of the in-line cylinders (1,2,3). Air passages (67,77) extend along said opposite sides to supply air from a supercharger (not shown) to the respective inlet ports. An air control valve (68) is operable to selectively control air supply to one or both of said air passages (67,77) whereby optimum combustion conditions are obtained for various engine load/speed conditions. A centrifugal supercharger arrangement is also disclosed, the supercharger being coupled to the engine crankshaft and interposed between the cylinder block and the engine flywheel.

Abstract: A two-cycle internal combustion engine configuration and control strategy in which the unburned hydrocarbon emissions in the exhaust gas are measured by a sensor in the exhaust manifold. The information from the sensor is used to control the outflow of air from a blower mixed with the fuel to vary the total volume of fuel and air to thus reduce unburned hydrocarbons in the exhaust gas.

Abstract: A scavenge system for a two cycle internal combustion engine that includes separate scavenge manifolds and riser scavenge passages extending therefrom to the individual scavenge ports so as to permit the establishment of a desired flow pattern within the engine without the flow to one scavenge port interfering with the flow to the other scavenge ports.

Abstract: An outboard motor including a supercharged internal combustion engine. The supercharger is positioned on a side of the crankcase opposite from the cylinders of the engine and is driven by the crankshaft through any of a plurality of different forms of drive arrangements that permit axially adjustment to maintain alignment.

Abstract: A two-stroke engine comprising at least one cylinder having a combustion chamber, an exhaust duct connected to the combustion chamber, at least one duct for the intake of fresh gas compressed by a compression device for delivering said fresh compressed gas, at least a first rotary valve opens and closes the exhaust duct and at least a second rotary valve feeds fluid into the combustion chamber.

Abstract: An outboard motor having an air compressor for delivering compressed air to a scavenging system for the engine. The air compressor is designed so that when the engine is not running, any moisture which may be present in the pumping cavity of the air compressor will drain out of the outlet opening of the compressor.

Abstract: An improved scavenging system for a two cycle internal combustion engine wherein the cylinder block of the engine is provided with an internal plenum chamber that surrounds the lower portion of the cylinders and which supplies the scavenge ports of the engine. In this way, it will be ensured that the proper air flow can issue from each scavenge port.

Abstract: A number of embodiments of outboard motors embodying pressure scavenged 2-cycle internal combustion engines. In each embodiment, a plenum chamber serves the scavenge passages of the engine and the pressure relief for a scavenge pump is provided by a pressure relief valve in the plenum chamber so as to reduce the opening and closing of the pressure relief valve due to pulsations caused by the engine operation. In one embodiment, the pressure is relieved by discharging the air to the exhaust system for silencing and also for cooling the exhaust gases. In other embodiments, the air for pressure relief is discharged to the atmosphere.

Abstract: Two embodiments of crankcase compression, internal combustion engines have air/fuel injection systems that include an air compressor driven by the engine and protected by the intake manifold. In one embodiment, the air compressor also drives a water pump and in both embodiments the induction system is designed so as to maintain substantially equal length runners for the individual crankcase chambers. This is accomplished by forming the check valves the communicate the runners with the crankcase chambers in parallel relationship to the respective runners.

Abstract: A four-stroke internal combustion engine for the otto and diesel cycle, characterized by incorporating a valve distribution for engines that use one or more ports near Bottom Dead Center. The four-stroke internal combustion engine comprises one or more cylinders each with a piston movable therein to define a combustion chamber and a port provided in a wall of each cylinder. The port is openable independently of an inlet valve and an exhaust valve to provide an additional route for the discharge of air or fuel/air mixture.

Abstract: A two-stroke-cycle spark ignited internal combustion engine operates with an exhaust valve that is controlled independently of crankshaft position and optimally for high power and low pollutant output in combination with a scavenging pump and fuel injector. The volume of combustible mixture is established at the point in the cycle when the exhaust valve is selectably closed with the piston traveling upwardly and decreasing the volume of the cylinder. Throttling losses are eliminated since the piston forces the scavenging air out of the cyclinder through the wide-open exhaust valve rather than the air being drawn into the cylinder against the reduced pressure caused by a conventional partially closed throttle plate. The volume of combustible air in the cylinder is determined by the point in the cycle at which the exhaust valve is closed and a correspondingly appropriate charge of fuel is thereafter injected into the cylinder.

Abstract: The invention relates to a more complex but considerably more emission-poor two-stroke engine than the conventional one. The HC-emissions become zero when completely burned. CO is controlled by the mixture ratio and NO.sub.x becomes very low owing to the built-in EGR.A super charger (20) presses air through the cylinder after the power stroke and dilutes the exhaust gases. A carburettor unit (21) is fed by the super charger and presses an overrich gas mixture into the cylinder at the beginning of the compression stroke. A slide gate (22) controls the connection between the carburettor unit and the cylinder.

Abstract: Several embodiments of V type supercharged two cycle internal combustion engines, in all embodiments the supercharger supplies air to a scavenge manifold that extends at least partially around the cylinder bores and which serves the cylinder bores through a plurality of scavenge passages, each of which is disposed to direct the intake charge away from the exhaust ports. In some embodiments, the supercharger is positioned out of the valley of the V and in one embodiment, the supercharger is positioned in the valley of the V.

Abstract: An two-cycle internal combustion engine that is particularly adaptable to the use of gaseous fuels. The engine is made suitable for running at high speed without an unwanted increase in pollution to the atmosphere through the use of a pressure differential of gasses as a closing force for the fuel injector valves.

Abstract: An improved internal combustion engine, particularly of the compression ignition, two cycle, aircraft type employing sleeve valves and a modular cylinder and removable cylinder head and retainer. The engine is turbocharged with the turbocharger separated into the compressor on one side of a V shaped cylinder array and the drive turbine on the opposite side. The exhaust is discharged through the center of the power output shaft making this engine particularly suited for pusher aircraft applications.

Abstract: An opposed piston two cycle internal combustion engine. The movement of the opposed pistons is transmitted to two cranks, the two cranks are interlocked together by gears. The gears maintain synchronized movement of the cranks and further act as an air pump to force air intothe intake manifold 20. A fuel charge is admitted into the intake tube 19 and is controlled by the rotary valve 17 for admission into a pre-compression crankcase 3. The rotary valve allows for further communication between the precompression crankcase 3 and injection crankcase 2 via passage 22. Air is introduced into the combustion space 10 via inlet ports 14. A fuel/air mixture is further controllably introduced via a fuel injection port 13 in the injection piston 4. The exhaust ports 15 are opened prior the timing of the intake ports 14 and close prior the closing of the intake ports 14 for superior scavenging.

Abstract: A two-stroke engine has a scavenge pump provided in an intake passage. A valve is provided in the intake passage downstream of the scavenge pump. When deceleration of a vehicle is detected, the valve is operated to partially close the intake passage.

Abstract: A two-cycle engine has an injector arranged for injecting fuel directly into a cylinder together with compressed air. The compressed air is injected from the injector after the closing of an exhaust port and before ignition, and fuel is injected in the stream of the compressed air in the injector within the period of the air injection.

Abstract: A rotary exhaust valve is provided in an exhaust passage of an engine, which is rotated by the engine. A valve phase control device is provided for changing the phase of the rotary exhaust valve. An actuator is provided for actuating the valve phase control device so as to change the phase of the rotary exhaust valve in accordance with engine operating conditions.

Abstract: A two stroke engine equipped with a mechanically driven supercharger in the intake passage downstream of throttle valve. A bypass air passage bypassing the supercharger is provided, and a bypass air control valve is arranged in the bypass air passage. When the engine is idling, the bypass air control valve is controlled so that the level of vacuum in the intake passage between the throttle valve and the supercharger is maintained at a constant value.

Abstract: A two-stroke internal combustion engine has an inlet port in the cylinder wall covered and exposed by the piston during reciprocation thereof in the cylinder and to which fresh air is supplied under pressure by a supercharger. An exhaust valve is mounted centrally in the cylinder head for controlled operation independently of the position of the piston. Fresh air forced into the cylinder by the supercharger when the inlet port is exposed by the piston during the exhaust stroke enables any residual unburned gases to burn completely and expels the gasses from the cylinder completely enabling operation of the engine at high compression with relatively low pollution.

Abstract: A port scavenged two cycle engine with a separate source of pressurized air has a valve between each port and the air supply to provide a high blowdown pulsing scavenging flow to the cylinders similar to that of a crankcase scavenged engine. Various arrangements with additional features are disclosed.

Abstract: A two-cycle engine has a scavenge pump provided in an intake passage, and a fuel injector provided for injecting fuel directly into a cylinder of the engine with compressed assist air. The quantity of intake air supplied by the scavenge pump and the quantity of the assist air are calculated in accordance with engine operating conditions. The quantity of fuel injected by the fuel injector is calculated based on the calculated quantities of the intake air and the assist air.

Abstract: A two-stroke engine comprises a cylinder which accommodates a piston and which has inlet and outlet ports, means for injecting fuel into the cylinder and control means for controlling the amount of fuel injected. The engine also includes a vent passage communicating with the interior of the cylinder and a first valve which is arranged to prevent communication between the interior of the cylinder and the vent passage and is connected to be opened and closed in synchronism with movement of the piston. Situated in the vent passage downstream of the first valve is a second throttling valve which is coupled to the control means and is arranged to be opened to an increasing extent to permit an increasing proportion of the inlet charge to be discharged as the control means is operated to reduce the amount of fuel which is injected into the cylinder thereby achieving homogeneous combustion at a constant air fuel ratio.

Abstract: A two-cycle engine has a scavenge pump provided in an intake passage, and a fuel injector provided for injecting fuel directly in a cylinder of the engine. A scavenge pressure sensor is provided in the intake passage for detecting a scavenge pressure. A plurality of data relative to quantity of air induced in the cylinder excluding escape air at scavenging the cylinder are stored in a memory. Quantity of air is derived from the memory in accordance with the detected scavenge pressure. Quantity of fuel injected by the fuel injector is calculated based on the derived quantity of air induced in the cylinder.

Abstract: A two-stroke engine has a scavenge pump provided in an intake passage. A continuously variable transmission is operatively connected between the scavenge pump and a crankshaft of the engine for operating the scavenge pump. An actuator is provided for changing the transmission ratio of the transmission. The actuator is operated by a controller so as to control the speed of the transmission ratio in accordance with load on the engine.

Abstract: The combustion engine of this invention is basically a two stroke engine at which each revolution of the crankshaft is subjected to a power stroke in each of the cylinders. However, this engine is chargable with turbo- or loader-pressure to increase its power considerably. For this purpose the engine has exhaust slots with an exhaust collection chamber on one end of the cylinders and the head cover on the other end of the respective cylinder. Each head cover is provided with at least one independent first inlet valve and a second independent inlet valve, while the passages to the inlet valves are completely separated from each other. Through the first inlet valve a flashing flow is passed to clean the cylinder from exhaust gases, while after closing of the first inlet valve, the second inlet valve is opened to pass a pre-compressed or loaded flow into the cylinder at a time when the exhaust slots are already closed.

Abstract: A two-cycle internal combustion engine is described having a combination of a combustion chamber portion at one end of the cylinder for receiving predetermined amounts of air and fuel; inlet ports for injecting fuel and compressed air into the upper end of the combustion chamber portion; exhaust ports in the cylinder for the conduction of exhaust gases and air from the combustion chamber portion, said exhaust port means being covered and uncovered by the side of the piston means and positioned to be fully uncovered at the bottom dead center position of the piston; a fuel/air mixing system in communication with the inlet ports the system having an air supply for providing a continuous supply of compressed air to the combustion chamber portion, a supply of compressed air generated by the engine, a fual supply for providing predetermined quantities of fual at specified intervals, and, a precombustion chamber for receiving and mixing the compressed air and the predetermined quantities of fuel and providing the co

Abstract: An internal combustion engine having as upper cylindrical gas chamber and a lower cylindrical gas chamber. The upper chamber having a bottom portion serving as a compression chamber and the lower chamber serving as a combustion chamber. A cooling jacket is provided between the two chambers to cool the sealing means therebetween. An inter-chamber passageway for direct communication between the bottom portion and the lower chamber is provided. A pumping turbine is provided for pumping fuel/air mixture into the bottom portion of the upper chamber.

Abstract: A two-cycle internal combustion engine comprises a cylinder head having two intake ports and an exhaust port opened to a combustion chamber, to which compresses fresh air is introduced via two intake valves. The intake and exhaust valves are operated in response to a crank angle. During an idling or light load running condition, an air control valve closes the second intake port. The exhaust valve is opened earlier than the second intake valve, and the first intake valve is opened later than the second intake valve, while the speed of the downward movement of the piston is relatively high. An exhaust gas swirl rotating around a cylinder axis is formed when the exhaust gas flows back into the condition chamber and the fresh air is slowly introduced via the first intake valve onto the exhaust gas swirl in the idling or light load condition. A large amount of fuel is rapidly introduced into the combustion chamber via the second intake valve in a heavy load condition.

Abstract: Two stroke gasoline spark ignition supercharged engine wherein air scavenging takes place without loss of fuel and full charge of air and fuel at optimum combustion ratio takes place for each power stoke with flywheel smoothed interrupted fuel injection for reduced power requirements. A modified valve design having a deflector lip is disclosed which further improves scavenging over the standard valve configuration.

Abstract: The efficiency and charge cooling characteristics of incoming air charges in the air box of a two-cycle diesel engine, preferably of the turbocharged and intercooled type, are improved by the addition of an air box flow guide insert which extends above the air box floor and directs the air smoothly from the air box inlet opening toward the cylinder inlet ports, thereby reducing turbulence and the possibility of heat exchange with engine coolant below the air box lower wall.

Abstract: A two-cycle, spark ignition engine is improved in order to eliminate the need for the typical reed valves and carburetor, while eliminating the carbon build-up inherent in mixing of the lubricant with the fuel mixture. Fuel and air are injected into the combustion chamber, and oil is injected into the crankcase, while eliminating communication therebetween. The improvement may be provided as a retrofit kit, for the standard two cycle engine, or the original casting of the engine may include the required modifications.

Abstract: A two-stroke diesel or gas fueled multi-cylinder engine utilizes a re-circulating type constant pressure feed lubrication system and is equipped with a supercharger or turbocharger combination connected in series to assist in charging the cylinders with air and also assists in scavenging the exhaust gases. The piston head is domed to assist the flow of the scavenging air in an upward direction toward the inside of the cylinder, and to facilitate the flow of exhaust gases to atmosphere. The scavenging port and exhaust port openings are formed in the same plane through the walls of the cylinder above the bottom dead center position of the piston head. The lower side of the scavenging port opening inclines inwardly and upwardly toward the cylinder wall so that the flow of scavenging air creates a turbulent action as it enters inside the cylinder for efficient scavenging of the exhaust gases.