Abstract: An engine idle and speed control arrangement incorporating a butterfly-type throttle valve. The throttle valve is disposed so that it is at a relatively small angle to a plane containing the throttle valve axis and extending perpendicular to the direction of air flow through the induction passage. The peripheral edge of the throttle valve is configured so as to avoid binding. Bypass idle air flow is provided around the throttle valve as to provide substantially the entire idle air speed requirements of the engine. This arrangement permits better idle control since the idle air-flow changes will be more uniform in response to given angular changes in the position of the throttle valve.

Abstract: An air regulated two cycle engine is disclosed which is designed to meet with the problems of a conventional two cycle engine, a poor fuel economy, an unsatisfied capability to limit pollution and a failure to produce a desired torque output, arising from the fact that a considerable portion of fuel gas is lost though the exhaust port that remains opened during a compress and admit stroke time interval of the engine. The improved engine is provided with an air intake port that is selectively opened by the piston moving to effect a compress and admit stroke to draw air from an outside atmosphere into the cylinder inside space. The engine that may otherwise be of a conventional design forces air so taken to transfer into the combustion chamber in a fuel transfer stroke time interval and then to regulate an exposition of fuel gas in the combustion chamber so as to maintain fuel gas unburnt therein to lie always in a layer substantially remote from the exhaust port.

Abstract: A two-stroke internal combustion engine having a crankcase provided with a crank chamber, a suction port which opens to the crank chamber, a scavenging passage opening into the crank chamber, and a crankshaft is provided with a flow control surface formed on an inner peripheral wall portion of the crank chamber which is capable of retarding the flow rate of unatomized raw fuel and which extends from the vicinity of the suction port to the vicinity of the scavenging passage. The flow control surface is comprised of a large number of intersecting unit ribs.

Abstract: A two cycle crankcase compression internal combustion engine wherein a single fuel injector is mounted in the cylinder block and can inject either directly into the combustion chamber or into the induction system through the crankcase chamber through a window in the piston. A control strategy is disclosed wherein the injection occurs primarily into the induction system during either or both of startup and low temperature.

Abstract: A crankcase scavenged two-stroke engine includes a piston reciprocably mounted in a cylinder. The cylinder wall has an exhaust port and a rear transfer port opposed thereto formed in it. The rear transfer port communicates with the interior of the crankcase via a rear transfer passage and is arranged to open before the exhaust port closes, whereby, in use, the cylinder is scavenged. An inlet duct is arranged to supply combustion air to the crankcase and a throttling valve is arranged to throttle the flow of air through the inlet duct. A carburettor is arranged to supply fuel into the inlet duct. The interior of the crankcase is divided into at least two separate crankcase volumes, a rich volume (V1,V2) and a lean volume (V3). Each crankcase volume communicates with the cylinder via a respective hole in the crankcase wall. The cylinder wall also has at least one lateral transfer port formed in it at a position between the rear transfer port and the exhaust port.

Abstract: A method and device for increasing the amount of fuel to an engine during acceleration is provided. A secondary source of fuel in addition to a first source of fuel is introduced into the engine during acceleration. The secondary source of fuel is introduced through a secondary fuel delivery line which is opened by a valve actuated in response to throttle control movement. In a first embodiment, the secondary fuel delivery line communicates with a fuel delivery area from which fuel is supplied to the first fuel source. The valve is pressed open by the throttle control along with a primary fuel source needle valve control, allowing fuel from the fuel delivery area to flow through the second fuel line in addition to the first fuel source. In second and third embodiments, the secondary fuel line communicates with an excess fuel return line. A valve extends across the fuel return line and secondary fuel line.

Abstract: A fuel increasing mechanism for supplying fuel to an engine positioned in an engine compartment defined by a hull of a watercraft is disclosed. The engine is arranged to power a water propulsion device associated with the watercraft and has a body defining at least one combustion chamber. The engine includes an intake system for routing air to the combustion chamber, the intake system extending from the body of the engine. The fuel increasing mechanism includes an accelerating pump for supplying fuel to air passing through the intake system, the accelerating pump positioned on a side of the intake system generally opposite the body of the engine.

Abstract: A fuel increasing mechanism for supplying fuel to an engine positioned in an engine compartment defined by a hull of a watercraft is disclosed. The engine is arranged to power a water propulsion device associated with the watercraft and has a body defining at least one cylinder. The engine includes an intake system for routing air to the cylinder, the intake system extending from the body of the engine at an angle offset from a centerline through the cylinder, whereby a space is defined above the engine between the body and intake system. The fuel increasing mechanism includes an accelerating pump for supplying fuel to air passing through the intake system, the accelerating pump positioned on a side of the intake system so as to be located in the space defined between the intake system and engine body.

Abstract: The invention is directed to a two-stroke engine for a portable handheld work apparatus such as a motor-driven chain saw. The engine includes a cylinder housing and a crankshaft journalled in shaft bearings. The cylinder housing is closed by a crankcase cover. Half shells are formed in the cylinder housing and the crankcase cover to accommodate the shaft bearings. Overflow channels are formed in the wall of the cylinder and lead from the crankcase to the combustion chamber. The overflow channels are open at their ends facing toward the crankcase cover and interrupt the support surface of the half shells formed in the cylinder housing. An adequate support of a small crankshaft bearing is ensured for an arrangement of several overflow channels. This is achieved in that the half shells are configured with a significantly larger diameter than the outer diameter of the shaft bearing and a support shell is seated in the free space between the half shell and the shaft bearing.

Abstract: An aspirating thermodynamic valve capable of controlling the flow of fuel mixture and air from the carburetor to the crankcase of a two-stroke engine includes a hollow body placed between the joint of the crankcase and the joint of the carburetor, along with suitably interpositioned seals. The valve includes a bush, the extremity of which is placed inside of the body and is cut out according to a predetermined inclination; furthermore, it includes a wall which is hinged by one end and is capable of closing the extremity.

Abstract: A two-cycle internal combustion engine including a carburetor, a crankcase provided with a crank chamber and a suction port, an insulator attached to the crankcase and provided with a suction passage for introducing the air-fuel mixture from the carburetor to the suction port, and a reed valve whose proximal end portion is fixed to the insulator so as to allow a free end portion thereof to be optionally press-contacted with the downstream side end face of the insulator, wherein the downstream side end face of the insulator is slanted by a predetermined angle, while the suction port is contiguously connected with the slanted downstream side end face of the insulator without substantially forming a stepped portion therebetween.

Abstract: A two-cycle internal combustion engine including a carburetor, a crankcase provided with a crank chamber and a suction port, an insulator attached to the crankcase and provided with a suction passage for introducing an air-fuel mixture from the carburetor to the suction port, and a reed valve whose proximal end portion is fixed to the insulator so as to allow a free end portion thereof to be optionally press-contacted with the downstream side end face of the insulator, thereby opening or closing the suction passage, wherein a rib is formed on a portion of the downstream side end face of the insulator which is in the vicinity of the free end portion of the reed valve in such a manner as to protrude into the suction port.

Abstract: An induction system arrangement for an engine powering an outboard motor is disclosed. The engine has a block defining at least one combustion chamber which a member movably mounted therein which is connected to a crankshaft for driving the crankshaft. A throttle body is connected to the block and has a throttle passage leading from an inlet to the block. An air plenum is positioned at the inlet of the throttle body. A fuel injector is mounted to exterior of the throttle body corresponding to each throttle passage. The air plenum has an air inlet through which air is supplied to the engine, the air inlet positioned on a side of the throttle body opposite the fuel injectors.

Abstract: A number of embodiments of induction system arrangements for a two cycle crankcase compression internal combustion engine having reed valve assemblies comprised of a mounting portion that defines a flow passage and a first caging member that divides the flow passage into first and second sections. A second caging member is affixed to the first caging member and the means which affixes it also affix a first reed valve for valving a valved opening in the first caging member. The valved openings in the caging members are generally rectangular in configuration and have a cross-sectional flow area approximately equal to the cross-sectional flow area of the intake passage in which the reed valve assembly is positioned. At least a pair of generally circular induction passages serve each reed valve member and a variety of different types of throttle valve arrangements and injection patterns are disclosed.

Abstract: A multicylinder internal combustion engine has an intake manifold with one or more auxiliary fluid distribution networks for directing byproduct fluids to each cylinder to insure balanced flow. The byproduct fluids include crankcase vapors and fuel vapors from an adsorption canister, and recirculated exhaust gas. The crankcase and purge vapors are mixed in a common network of flow passages formed by grooves formed into the face of an intake manifold mounting flange, with the exhaust gas in a separate sealed network of grooves. Assist air flow to the injector ports is directed through yet another network of grooves in the flange face.

Abstract: A fuel injected induction system for a crankcase compression, two-cycle, V-type internal combustion engine includes a plurality of throttle valves corresponding in number to the number of crankcase chamber of the engine. Each throttle valve communicates with a dedicated intake passage that directly communicates with a respective crankcase chamber. At least one fuel injector is positioned within each intake passage in order to form the air/fuel charge delivered to the crankcase chamber. The corresponding number of throttle valves, fuel injectors and crankcase chambers allows for enhanced control over the air-fuel ratio delivered to each of the cylinders, as well as improved consistence of the air-fuel charge delivered to each of the cylinders of the engine.

Abstract: A two-cycle engine having a plurality of combustion chambers, each chamber in communication with an air/fuel mixture delivery passage via a crankcase chamber, is disclosed. The engine includes a system for delivering fuel which precipitates out of the air/fuel mixture within the delivery passage to the combustion chambers. The system includes at least one fuel catch in the form of a trough positioned in each delivery passage and a fuel delivery passage extending from the catch to the combustion chamber.

Abstract: The present invention is an air-blast fuel injection two-stroke engine comprising at least one cylinder (1) in which moves a piston (2) defining a combustion chamber (14) and a pump crankcase (5) forming a continuation of the combustion chamber and separated therefrom by the piston (2), at least one main air inlet (7) in the pump crankcase that can be equipped with a first nonreturn device (6), a device for introducing the fuel mixture at a given pressure, comprising a mechanism (20) for opening and for closing a port (12) for introducing the fuel mixture into the combustion chamber (14), a container (15) connected to the introduction port (12) and containing the fuel mixture under pressure. The engine further comprises a mechanism (30-34) for sucking and introducing the fuel mixture under pressure into the container.

Abstract: A method and device for increasing the amount of fuel to an engine during acceleration is provided. A secondary source of fuel in addition to a first source of fuel is introduced into the engine during acceleration. The secondary source of fuel is introduced through a secondary fuel delivery line which is opened by a valve actuated in response to throttle control movement. In a first embodiment, the secondary fuel delivery line communicates with a fuel delivery area from which fuel is supplied to the first fuel source. The valve is pressed open by the throttle control along with a primary fuel source needle valve control, allowing fuel from the fuel delivery area to flow through the second fuel line in addition to the first fuel source. In second and third embodiments, the secondary fuel line communicates with an excess fuel return line. A valve extends across the fuel return line and secondary fuel line.

Abstract: To avoid stalling of a two-stroke internal combustion engine as its orientation is changed upon a change of direction in which a working machine such as a chain saw is held, non-atomized fuel is prevented from flowing precipitously into the combustion chamber of the engine. The engine comprises a crank case forming a crank chamber which has an intake port opening into the crank chamber, and a flow control feature at the circumferential inner surface of the crank chamber in the vicinity of the intake port for retarding flow of non-atomized fuel.

Abstract: A fuel induction system for an internal combustion engine which includes a throttle valve that is positioned substantially open under idle and near idle engine running conditions. The system includes means for disabling one or many of the cylinders in order to maintain a low engine rotational speed at idle and near idle and also means for selectively disabling the cylinders in such a manner as to provide the smoothest running engine possible in those instances where one or many of the engine's cylinders are disabled.

Abstract: A two-stroke internal combustion engine in a working machine such as a chain saw has been prone to stalling when the stance of the machine was changed from slanting down to slanting up. Such stalling is minimized when lower longitudinal scavenging passage in the cylinder block of the engine have smaller cross section as compared with upper scavenging passage, and when the crank chamber of the engine includes a flow restricting portion for impeding the flow of liquid fuel into the lower scavenging passage when the stance is changed. The engine has a cylinder block (12), a crankcase (20), scavenging passages (27, 27), and a flow restricting portion (40) on an inner peripheral surface (22a) of the crank chamber (22).

Abstract: A fuel injection and ignition control system for a two-cycle crankcase compression engine wherein both fuel injection and ignition timing are controlled by sensed engine running characteristics at a predetermined crankshaft position. The timing of the ignition is controlled by the same parameter at which the fuel injection was controlled, so that the timing of ignition and amount and duration of fuel injection will be optimized for the same engine running condition.

Abstract: An improved fuel delivery system, method and apparatus providing a hybrid carburetor and direct fuel injection system, utilizing the best of each for different engine operational modes to thereby meet emission requirements for small hand-held two-cycle engines using standard two-stroke gasoline and oil premix fuel. A diaphragm carburetor and associated diaphragm fuel pump operates alone to supply a proper A/F idle mixture sufficient only for engine power at start-up idle and off idle (light load). This engine aspiration carburetor fuel delivery system is operated continuously, and then at part (off idle-light load) and wide open throttle (W.O.T) the same is combined with operation of a direct cylinder fuel injection system, using a second stage pressure boost peristaltic type pump and fuel injector nozzle, that is engine self-regulated and driven to operate only at part-throttle and W.O.T. to thereby supply most of the engine fuel demand in these operational ranges.

Abstract: A four-cycle internal combustion engine wherein the piston connecting rod crankshaft and crankcase chamber are formed so that the crankcase chamber acts as compressor. An induction system supplies atmospheric air to the crankcase chamber and a pressure conduit supplies air from the crankcase chamber to the engine intake valve. A plenum chamber is disposed within this pressure conduit and pressure control is possible by bypassing air form the plenum chamber to the atmospheric air inlet. A throttle valve is positioned downstream of the plenum chamber so as to improve engine braking and charge forming systems are disclosed that permit a compact assembly and good response under all engine running conditions.

Abstract: A fuel system for an outboard motor includes a low-pressure fuel transport subsystem and a high-pressure fuel delivery system. The fuel transport system guides fuel from a fuel tank located in the hull of the watercraft to a fuel tank located with a cowling surrounding the engine. The high-pressure fuel delivery system supplies fuel to a fuel rail that communicates with fuel injectors of the engine's induction system. The induction system communicates with crankcase chambers on a side of the engine opposite of the engine cylinders. The low-pressure fuel transport subsystem is located on a side of the induction system opposite of the high-pressure fuel delivery subsystem. This layout minimizes the flow path length from the fuel tank within the cowling to the fuel rail. It also reduces the girth of the engine and simplifies the arrangement of the fuel hoses of the fuel supply system.

Abstract: A fuel induction system for an internal combustion engine which includes a throttle valve that is positioned substantially open under idle and near idle engine running conditions. The system includes means for disabling one or many of the cylinders in order to maintain a low engine rotational speed at idle and near idle and also means for selectively disabling the cylinders in such a manner as to provide the smoothest running engine possible in those instances where one or many of the engine's cylinders are disabled. The number of cylinders disabled also depends on the load driven by the engine.

Abstract: Air adjustment to a multi-cylinder two-cycle fuel injected engine, such as marine outboard type, is accomplished by a slide throttling control valve in conjunction with an upstream air velocity stack of variable thickness spacers.

Abstract: A fuel injection system for an engine having a reed type valve in the induction system. The injection system is designed and controlled so that the fuel that is injected is injected substantially entirely before the reed type valve is closed. The time of closing of the reed type valve is determined either by measuring the pressure differential or by recording data indicative of the valve closing in response to various engine running conditions such as speed and/or load.

Abstract: A fuel injection control system accurately determines the amount of fuel to be injected by compensating the measured crankcase pressure in view of various conditions including intake air condition, effects of exhaust gas pressure by other cylinder and others, with use of one pressure sensor. The fuel injection control system includes a pressure sensor installed in a cylinder of the engine for detecting crankcase pressure, a fuel injector for injecting fuel to the engine on the basis of the crankcase pressure detected by the pressure sensor, and a device for compensating the amount of fuel injected from the fuel injector depending on the condition of intake air in the crankcase. Another aspect of the system additionally includes controlling timing for detecting the crankcase pressure by the pressure sensor depending on the rotation rate of the engine.

Abstract: A fuel induction system for an internal combustion engine which includes a throttle valve that is positioned substantially open under idle and near idle engine running conditions. The system includes means for disabling one or many of the cylinders in order to maintain a low engine rotational speed at idle and near idle and also means for selectively disabling the cylinders in such a manner as to provide the smoothest running engine possible in those instances where one or many of the engine's cylinders are disabled. Smooth transition from one mode to another is achieved by fuel and ignition corrections.

Abstract: A two-cycle engine of the spark ignition type is provided wherein a mixture in a combustion chamber can be compressed and self-ignited at least in a low load operation region to effect an activated heat atmosphere combustion. In a transition operation region between the activated heat atmosphere combustion region and an ordinary spark ignition combustion operation region, the mixture can be ignited by a spark ignition at a timing earlier than the spark ignition timing in the ordinary spark ignition combustion operation region to stabilize the combustion condition and eliminate abnormal combustion noise and the harmful effects of heat. A throttle valve opening of a throttle valve manually operated is detected by a throttle valve opening sensor formed from a potentiometer or the like while an engine speed is detected by an engine speed sensor, and they are inputted to a CPU. The CPU operates in accordance with a control graph of FIG.

Abstract: An improved idle speed control arrangement that embodies an idle air passage formed in a member of the induction system that is downstream of the throttle valves. The idle air passage is formed by a groove in a face of the member that is closed by engagement with another member of the induction system. The idle speed is controlled by controlling the flow of air to the idle passage from an atmospheric air inlet.

Abstract: A polymer composite reed for a reed valve is provided, wherein the reed has improved mechanical properties as a result of its construction and is highly resistant to chemical and thermal attack. The improved mechanical properties of the reed are primarily due to the reed being reinforced with two plies of fabric having a harness satin weave, which provides the reed with a flexural modulus that is substantially greater in one direction of the reed. The chemical and thermal properties are primarily due to the semicrystalline thermoplastic material from which the reed is formed. In addition, the thermoplastic material enhances the fracture toughness of the reed to improve the durability of the reed. As a result, the reed is highly suitable for applications requiring long life under high speed, cyclic loading, such as that found in two-stroke and four-stroke internal combustion engines for the automobile industry.

Abstract: A number of embodiments of induction system for fuel injected outboard motors. In each embodiment the fuel injectors are bounded on at least two sides by the induction system so that the airflow through the induction system will cool the fuel injectors.

Abstract: An auxiliary carburetion device in direct fuel injection engines, to be positioned in correspondence with a main duct (12) feeding air to the engine crankcase (10), a throttling member (38) being located in the main duct (12). The device includes a block (13) containing at least one selective regulating element (15, 25) positioned in a connection duct (19, 20; 30) which is connected at one end to a vessel (14; 45, 51) containing a constant predeterminable amount of fuel and to a mixing air duct (23, 32), and at the other end to the main duct (12) feeding the crankcase (10).

Abstract: A fuel injection system for an internal combustion engine is provided wherein fuel supply compensation for low speed, low load or abnormal conditions is variable for a multi-cylinder configuration having one or more cylinders ceased or reduced in operation. Of particular utility in a vertical cylinder bank with compact space for exhaust gas collection and discharge, such as in an outboard motor, said fuel compensation relies upon engine parameters including engine speed and fuel-air ratio to improve engine performance.

Abstract: An adiabatic intake insulator inserted into a portion for connecting a carburetor to a small two-cycle gasoline engine or the like in which the generation of cracks due to stress concentration when bolts are fastened are restrained and the looseness of the fastening member due to the shortage of fastening torque is prevented. The intake insulator comprises: portions for supporting and securing a carburetor; an intake passage through which air-fuel mixture from the carburetor is introduced to the engine; portions for securing the intake insulator to the engine each comprising a through hole for a bolt and a counterbore for accommodating a head of the bolt; and a channel formed on a circumference of a bottom of the counterbore.

Abstract: A fuel injection system for a two-stroke cycle engine capable of keeping an air-fuel ratio of an air-fuel mixture for combustion at a low engine speed optimum to improve startability of the engine in a cold district. The system includes a low-speed basic injection time increment setting unit for setting a low-speed basic injection time increment Tfi depending on an engine speed N and a throttle opening .alpha., a low-speed crankcase temperature correction factor setting unit for setting a low-speed crankcase temperature correction factor KLc, time correction factor setting units for setting a time correction factor Kt which is decreased with an increase in crankcase temperature, as well as with lapse of time, and a low-speed injection time increment setting unit for setting a low-speed injection time increment TiL by multiplying the increment Tfi by the correction factors KLc and Kt.

Abstract: This invention relates to reciprocating piston machines which use the crankcase for pumping air or charge. The connecting rod with extension partitions the interior of the crankcase including the lower cylinder into two varying volumes during a portion of each revolution of the crankshaft. A unique feature is that the designer can choose the capacity of the crankcase pump independent of other significant design parameters such as the ratio length of connecting rod/stroke and the ratio stroke/bore.

Abstract: A two-stroke internal combustion engine comprising an engine block, a plurality of crankcases and including a mounting surface having therein a plurality of inlet openings each communicating with a respective one of the crankcases, a throttle housing defining a throttle passage and including a plenum mounting surface, a throttle valve in the throttle passage, and a plenum member which is separable from both the engine block and the throttle housing and which defines a plurality of intake passages each having an outlet end communicating with a respective one of the inlet openings and each having an inlet end communicating with the throttle passage such that the intake of the engine can be tuned solely by modifying the configuration of the plenum member.

Abstract: An improvement for use on a V-type two-cycle engine having two rows cylinders with air intake passages aligned generally symmetrically on either side of an engine crankshaft is disclosed wherein the attachment of the air intake passages to the engine crankcase is rigidified so as to suppress the vibrations generated by the air intake system. This structural interconnection can take the integrally forming the intake passages with the crankcase, securing the between the cylinder rows end a support member formed integral with the crankcase and/or supporting the intake passages to the crankcase at their upstream ends through an air intake box. In addition, the air intake passages may be integrally formed with bearing supports for the engine crankshaft to enable the crankcase to be formed from more than one piece which can be readily detached for inspection and maintenance purposes.

Abstract: A motorcycle powered by a two cycle crankcase compression fuel injected internal combustion engine. The injection system for the engine includes a main fuel air/injector that injects fuel directly into the combustion chamber and a second or auxiliary fuel injector that injects fuel into the induction system for the engine. Control means control the fuel injectors so that the second or auxiliary fuel injector supplies fuel only during starting and high load, high speed conditions. The engine components are laid out in such a way that the spark plugs of the engine and the fuel injector will each be exposed to unobstructed air flow for cooling.

Abstract: A motorcycle powered by a two cycle internal combustion engine having an improved induction system that has a vertically extending intake pipe so as to permit a wide latitude of leaning of the motorcycle without interference from the induction system. The induction system serves the crankcase of the engine through a rotary plate type valve that has a helical connection to the engine output shaft so that the timing of the opening and closing of the intake port can be adjusted. A servo motor adjusts the helical connection under the CPU so that the timing change mechanism need not be powered directly by the engine.

Abstract: The air/fuel charge supplied to the cylinder rows of a V-type two-cycle engine is separately determined based on the air intake conditions associated with each of the cylinder rows. The air/fuel supply system according to the present invention promotes good mixing and misting of the fuel and air and delivers an optimal amount of fuel to each of the cylinders such that imbalances in the combustion and output of the two cylinder rows are minimized.

Abstract: An induction system for a crankcase compression, two cycle, V-type internal combustion engine having a compact configuration. The engine cylinder banks are disposed at a V-angle and define a valley therebetween in which the induction system is positioned. A fuel injector is supplied for spraying fuel to each of the intake ports and the fuel injectors are disposed in the valley of the engine each between the respective induction system and the cylinders served by it.

Abstract: In a two-cycle engine provided with crankshaft controlled fuel injection, fuel is supplied from a fuel tank to an inlet (23) having an adjusting means. The fuel flows via a connection (27) to a passage (39) in the crankshaft (13). Gaskets and O-rings are provided to seal off against the crankshaft and crankcase. The positions of the connection (27) and the crankshaft passage (39) are selected so as to obtain communication when underpressure prevails in the crankcase whereby fuel is sucked in and thrown out by centrifugal force via a nozzle (31).

Abstract: A fuel injection system and method of operating it for a two-stroke crankcase compression internal combustion engine. The engine is provided with a main fuel injector that injects fuel directly into the combustion chamber and an auxiliary fuel injector that injects fuel into the inductions system. A throttle valve controls the flow through the induction system. The system includes a detector for detecting an abnormality in the operation of the main fuel injector and shuts the main fuel injector down when this occurs and increases the amount of fuel supplied by the auxiliary fuel injection. When this abnormal operating condition occurs, the degree of opening of the throttle valve is also reduced.

Abstract: A diesel engine operating on the two cycle crankcase compression principle and having a means for reducing nitrous oxide emissions under low and medium range speeds. This is done by throttling the scavenge air flow which can be accomplished either by throttling the air admitted to the crankcase chamber or bypassing a portion of the compressed air from the crankcase chamber back to the induction system. In addition, an exhaust control valve is provided for raising the compression ratio and the injection timing is advanced when the scavenge air is reduced so as to further improve the control of hydrocarbon and carbon monoxide emissions.

Abstract: A two-stroke internal combustion engine comprising an engine block, a plurality of crankcases and including a mounting surface having therein a plurality of inlet openings each communicating with a respective one of the crankcases, a throttle housing defining a throttle passage and including a plenum mounting surface, a throttle valve in the throttle passage, and a plenum member which is separable from both the engine block and the throttle housing and which defines a plurality of intake passages each having an outlet end communicating with a respective one of the inlet openings and each having an inlet end communicating with the throttle passage such that the intake of the engine can be tuned solely by modifying the configuration of the plenum member.