Abstract: A throttle body (12), for an air intake system of a vehicle, including a housing (14) formed of a thermoplastic material and including a pair of throttle shaft bearing pockets (24, 26) extending from a main bore (16) of the throttle body. The bearing pockets (24, 26) each include a generally cylindrical wall (34) of a diameter to allow for a press fit of throttle shaft support bearings (28, 30) therein. After insertion, a swaging process secures the bearings (28, 30) into the pockets (24, 26) by forming lips (40) around the bearings. The walls (34) may include axial grooves (36) to allow for a more controlled swaging operation.

Abstract: A throttle valve for an internal combustion engine includes a body having a throttle bore defining an axis. A throttle plate for controlling air flow through the throttle valve is molded within the throttle bore, thereby providing a relatively exact throttle plate to throttle bore positional relationship The throttle plate may be integrally molded within the throttle bore and attached to the throttle body. The throttle plate is subsequently detached from the throttle body for relative rotation within the throttle bore. To facilitate detaching of the throttle plate, the plate may be weakened about is periphery. The throttle plate may be also formed with a bend for reducing throttle plate sticking upon rotation from an idle position and for controlling air leakage when the throttle plate is in the idle position. Further, the throttle plate may include a wedge to control air flow through the throttle bore and reinforcing ribs to further control the deflection of the throttle plate.

Abstract: A plastic throttle body valve including a valve body having an interior passage way connecting an inlet and an outlet of the valve body. The valve body includes an arcuate surface through which the inlet is provided, and a closure member pivotally attached to the valve body for selectively opening and closing the inlet. The valve has the advantage that there is no obstruction in the air stream when the valve is wide open.

Abstract: An internal combustion engine includes an engine cylinder; a first intake port leading to the cylinder for introducing combustion gases thereinto; a first intake valve situated at the cylinder in the first intake port; a second intake port leading to the cylinder for introducing combustion gases thereinto; a second intake valve situated at the cylinder in the second intake port; and a throttle arrangement situated in the second intake port for varying a flow passage cross section thereof. The throttle arrangement includes a flat sliding member movable in a direction of motion thereof perpendicularly to the longitudinal axis of the second intake port for varying the flow passage cross section thereof.

Abstract: A throttle actuator including driving means having a stator provided with a stator winding and a rotor provided with a sun gear at a rotating shaft thereof, planetary speed reducing means having the sun gear at the rotating shaft, a stationary gear installed at an outer periphery side of the sun gear and a planet gear in mesh with the sun gear and the stationary gear for performing a planetary motion by rotating the rotor, a planetary gear support pin supporting the planet gear and performing a revolutionary motion along with the planet gear, and a planetary arm disposed between the planetary gear support pin and a valve shaft of a throttle valve.

Abstract: A fuel injection system of an internal combustion engine of a vehicle such as motorcycle comprises a throttle body of a cylindrical structure having a passage for supplying a fuel-air mixture to a combustion chamber of an engine, a disc-shaped throttle valve disposed in the passage to be rotatable so as to regulate an amount of air flowing through the passage, and an injector means mounted on a peripheral wall of the passage and adapted to inject fuel in the passage at a portion of a downstream side of the throttle valve with respect to an air flow in the passage. The throttle valve is provided with a through hole opened to both surfaces of the throttle valve, and the through hole being formed at a portion on an injector location side with respect to a rotational axis of the throttle valve so that an axis of the through hole substantially accords with, or intersects, a central axis of a fuel injected from the injector when observed from the injector location side.

Abstract: An intake valve control apparatus for an internal combustion engine eliminates adverse effects due to accumulation of deposit materials downstream of the throttle valve to always ensure a smooth movement of the throttle valve. The apparatus has a body member forming an intake air passage and a throttle valve rotatably mounted therein. The throttle valve has a first outer circumference which rotates toward the upstream side thereof and a second outer circumference which rotates toward the downstream side thereof. A wall surface inside the body member opposite the first outer circumference of throttle valve is spherical, and wall surface of the body member opposite the second outer circumference of the throttle valve is cylindrical.

Abstract: A barrel throttle valve assembly (20) for use in an air intake system of an internal combustion engine. The barrel throttle valve assembly (20) includes a barrel (32) mounted within a housing (22), with the barrel (32) preferably including an upstream orifice (42), and idle notch (44) and a downstream orifice (46) for controlling the flow of idle air through the valve when the barrel (32) is in a substantially closed position, thus increasing the sensitivity of the valve at idle conditions. Also, preferably, a seal (48) and spring (54) is employed to reduce air leakage around the barrel (32).

Abstract: A throttle body (10) for use with an air intake system of an internal combustion engine. The throttle body (10) includes a throttle valve (18), which includes a throttle plate (20) mounted to a throttle shaft (22) within a slot (26). The throttle shaft also includes a notch (32) extending between the slot (26) and the surface of the throttle shaft (22). The notch (32) allows for ease of manufacturing and assembly and also allows for a slight increase in air flow past the throttle valve with minimal reduction in bending strength of the shaft.

Abstract: A position sensor for a throttle valve, the position sensor including a housing having a partition wall separating an attachment chamber and a sensor accommodating chamber, each of which include an outer opening. The partition wall defines a central opening. The housing is connected to a case of the throttle valve such that the outer opening of the attachment chamber is closed by the throttle valve case. A drive shaft of the throttle valve is connected to a driven shaft mounted in the attachment chamber, the driven shaft being rotatably supported on the partition wall. A sliding-element receiver is located within the accommodating chamber and is connected through the central opening in the partitioning wall to the driven shaft. The driven shaft and the sliding-element receiver cooperate to close the central opening of the partition wall. A insulating substrate is disposed within the accommodating chamber opposite to the sliding-element receiver.

Abstract: In order to provide an accurate traction control by closing a second throttle valve provided in series to an accelerator-operated ordinary throttle valve, with a simplified actuator, a control system for reducing a vehicle driving torque employs one or more sensors for sensing a second vehicle operating parameter representing a road surface friction coefficient (.mu.) or a driver's command for acceleration, in addition to sensors for sensing a first vehicle operating parameter representing a drive wheel slip. When the road surface friction coefficient is high or when the driver depresses the accelerator pedal hard, the control system restrains the closing operation of the second throttle valve in accordance with the second parameter even though the closure of the second throttle valve is requested by the first parameter.

Abstract: Disclosed is a throttle valve control device for internal combustion engines which has good measuring accuracy and improved controllability of an air flow rate. A throttle valve is rotatably attached to a throttle body through a throttle shaft. The throttle body has an inner surface of straight bore type that the center of rotation of the throttle valve is positioned on a line connecting the centers of an upstream opening and a downstream opening of the throttle body. The throttle body has a spherical inner surface X2 in an idle speed control area .theta.2 near the fully closed angle of the throttle valve. The throttle body also has, in an area .theta. subsequent to the spherical inner surface X2, an inner surface X3 having a composite form made up of a spherical surface and a cylindrical surface substantially parallel to a flow of intake air.

Abstract: A control valve arrangement for a three-valve-per-cylinder internal combustion engine that redirects the flow through a siamese-type intake passage when in its closed position so as to generate a higher velocity to the intake charge and redirect the flow so as to generate turbulence in the combustion chamber. A number of embodiments of control valves are disclosed, each being of the plate-type and being mounted in a generally oval intake passage on a control valve shaft in such a way that the control valve shaft provides minimum obstruction to the flow through the intake passage, regardless of its position.

Abstract: Electronic engine management systems have a plurality of individual components, some of which are relatively far away from one another. Electrically connecting the individual components, particularly to an electronic control unit therefore requires relatively long electrical connecting lines and relatively many plug connection. The apparatus includes a plurality of components, that is, at least one throttle device accommodated rotatably in a throttle valve housing and actuatable by a throttle valve control motor, an electronic control unit, a regenerating valve, and/or an air flow rate meter, which according to the invention are accommodated in a common housing as a premountable structural unit. The apparatus of the invention is intended in particular for mixture-compressing internal combustion engines with externally supplied ignition.

Abstract: Disclosed is a fuel injection system with a variable injection position, including an accelerating pedal, a throttle valve for regulating the amount of intake air in response to vehicle speed, a fuel distribution pipe, an injector fixed to the fuel distribution pipe, an accelerating lever which rotates in response to pedal effort of the accelerating pedal, a pinion which rotates in accordance with the rotation of the accelerating lever, and a rack which slides horizontally in response to the rotation of the pinion to vary the position of the injector that is fixed on the fuel distribution pipe.

Abstract: A throttle for an internal combustion engine wherein intake runners (18) include slots (24) through which a slide throttle plate (26) is mounted. The throttle plate includes openings (28) selectively aligned with the runners (18) by an actuator (32) to control the air flow into the engine intake ports (14). Actuation linearly across the runners (18) provides for tumble port flow control and idle control, as well as port deactivation.

Abstract: A combustion air intake system for an internal combustion engine has an intake manifold which supplies intake air to the engine through pairs of differing length intake runners. A valve assembly is disposed between the intake runners and the engine and includes a molded composite housing having pairs of combustion air through passages which are in flow communication with associate pairs of intake manifold runners. An axially extending valve bore defines an axis through the valve housing and bisects the through passages. Molded integrally within the valve housing is a molded composite valve member having an axial valve shaft, disposed in the valve bore, and integral valve plates, disposed in predetermined through bores. The valve member is rotatable in the valve bore to open and close the valve plates for regulation of air flow through the predetermined through bores and associated intake runners.

Abstract: A keep-back recess for blocking water, which is likely to be transmitted to a throttle valve along an inner peripheral surface of an intake pipe, is formed at an inner surface of a throttle body. The keep-back recess collects and stores water so that the throttle valve is prevented from freezing without leading engine cooling water in the throttle body.

Abstract: A plastic throttle body valve including a valve body having an interior passage way connecting an inlet and an outlet of the valve body. The valve body includes an arcuate surface through which the inlet is provided, and a closure member pivotally attached to the valve body for selectively opening and closing the inlet. The valve has the advantage that there is no obstruction in the air stream when the valve is wide open.

Abstract: A bearing is fixed in a housing in such a way that it is fixed axially relative to a throttle flap shaft which remains rotatable relative to the bearing. The throttle flap shaft can then be gripped relative to the bearing, in a bearing recess of the throttle flap housing. The throttle device is suitable particularly for vehicles having a throttle-type internal combustion engine.

Abstract: A fuel injection system for an internal combustion engine utilizing manifold injection with the injector positioned downstream of a flow controlling throttle valve. The throttle valve is provided with a flow passage that intersects the spray axis of the injector to provide good fuel vaporization and distribution even at low speeds.

Abstract: A carburettor metering system comprises a fuel evaporator 113 consisting of porous parallel plates 114 with their lower portions immersed in fuel 121, fuel metering means 122 for supplying fuel to the evaporator 113, and a laminar flow air restrictor 128 comprising a series of parallel plates 127 separated by spacers and defining narrow gaps between the plates 127. Such an arrangement enables a substantially constant air/fuel mixture strength to be obtained over a wide range of air flow rates in single cylinder engines. Furthermore the supply of mixture to the engine by way of an exit tube 126 may be controlled by a valve member 132 coupled to the engine governor so that the rate of flow of mixture varies in dependence on the load, and additionally so as to change the system between two modes of carburettor operation, namely lean operation, which is provided up to about three quarters load, and rich operation in which additional fuel is supplied to the evaporator 113.

Abstract: An induction system and control arrangement for a three valve per cylinder engine, wherein the induction passages are tuned to provide different effective lengths for different engine running conditions. In addition, a control valve arrangement is provided for controlling the flow to the combustion chambers through the valve seats to generate unrestricted flow under high-speed, high-load conditions and tumble and/or tumble and swirl for promoting turbulence under low-speed, low-load conditions.

Abstract: Throttle butterfly, especially a throttle butterfly in an intake channel of an internal-combustion engine which has a throttle butterfly shaft extending concentrically to a central axis. The throttle butterfly as well as the housing surrounding it have sealing surfaces facing one another.

Abstract: An inlet duct and seal assembly is disclosed having, as its preferred application, the attachment of an intake air transfer duct to the throttle body of an internal combustion engine. The throttle body is provided with an inlet opening about which extends an annulus defining an outer annular wall. The inlet air duct has an opening which corresponds in diameter to that of the annular outer wall. A seal is disposed in the duct opening and includes an inwardly, radially directed wiper seal which is flexibly deformed between the annular wall and the duct opening when the duct opening is engaged over the throttle body inlet.

Abstract: A throttle body assembly (10) including a throttle plate (22) mounted in the main bore (16) of the throttle body. Either the throttle plate, the bore or both are pre-sludged around the throttle plate/bore interface, using a sealant (24) that is cured with Ultraviolet energy, in order to maintain better air flow control over the life of the throttle body.

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 control for a throttling member, for example a throttle butterfly of an internal combustion engine. The actuating device has an actuating member which is designed as a plastic part and is molded onto one end of an adjusting shaft by means of an inner fixing sleeve and a recess made in the adjusting shaft in the form of a slot which is filled with plastic, thus allowing reliable torque transmission. The actuating device is suitable for throttling devices of mixture-compressing, spark-ignition or air-compressing, self-ignition internal combustion engines.

Abstract: A anti-turbo device including a housing unit that has a first end with an intake pipe interconnected, and a second end with an exhaust pipe interconnected. The housing unit is capable of having a flow of air flowing from the intake pipe through to the exhaust pipe. An air pedal projects from a top portion of the housing. The air pedal has a short member interconnected an elongated member. The short member is coupled with a linkage of a gas pedal. Lastly, a baffle is included. The baffle has a top side with a distal end of the elongated member, of the air pedal, interconnected. The air pedal is capable of moving the baffle when the linkage is moved by the air pedal. The baffle has a bottom peripheral edge that is spaced from a bottom interior portion of the housing. The bottom peripheral edge is capable of modulating the air flow through the housing, when the linkage moves the air pedal.

Abstract: A throttle device is described, in particular a throttle valve in a suction pipe of an internal-combustion engine. This throttle device consists of a housing, a throttle valve control, a position sensor and a throttle valve fastened to a throttle valve shaft. The throttle device is arranged between the clean-air-side air filter connection and the suction pipe of the internal-combustion engine. The air filter connection and/or the suction pipe consist of a plastic material, and the individual elements of the throttle device are constructed as modules which can be fitted, screwed or clamped together.

Abstract: A port throttle valve and an intake system incorporating the valve is disclosed. The valve is disposed between one of two intake runners delivering air to the intake port of an engine cylinder and includes a base member having an opening for delivery of air therethrough. The base includes a track in which is slidingly disposed, two adjacent valve plates each having an opening for registry with the opening in the base member to allow for the passage of air. When moved, in opposite longitudinal directions, the edges of the openings in the valve members move towards one another to terminate registry of the openings with the opening in the valve body.

Abstract: A multicylinder internal combustion engine has an intake port for each cylinder, with the flow through the intake port being controlled by a port throttle having a sliding plate mounted normally to the longitudinal axes of the intake ports and having windows which may be selectively indexed with the intake ports so as to direct charge air either symmetrically or asymmetrically into the cylinders.

Abstract: A throttle-valve housing of plastic has a metal insert which achieves dimensional stability in the region of the throttle valve. The throttle-valve housing is formed of plastic with a cavity bounded by an inner wall surface. In the wall there is arranged a metal insert which is covered on all sides by the plastic material and effects a stabilization of the plastic material, so that distorting, shrinking or the like is prevented and dimensional accuracy of the inner wall surface is ensured. The novel throttle-valve housing is simple to produce and has a high dimensional stability in spite of being formed from plastic material. The throttle-valve housing is suitable for internal-combustion engines of motor vehicles.

Abstract: The present invention provides a throttle valve opening degree sensor for detecting the opening degree of a throttle valve used for an internal combustion engine wherein a rotor shaft capable of interlocking with a throttle valve has a cylindrical covering portion having an outer circumferential cylindrical body at the outer end, the cylindrical covering portion covering the outer end of the bearing portion exposed to the base portion of the housing and having an elastic engaging portion having cross-like splitted grooves at the top end and a square outer periphery, and the rotor has a square engaging hole capable of fitting the elastic engaging portion, the elastic engaging portion being fitted to and elastically abutted against the engaging hole thereby securing the rotor to the rotor shaft.

Abstract: A carburettor metering system comprises a fuel evaporator 113 consisting of porous parallel plates 114 with their lower portions immersed in fuel 121, fuel metering means 122 for supplying fuel to the evaporator 113, and a laminar flow air restrictor 128 comprising a series of parallel plates 127 separated by spacers and defining narrow gaps between the plates 127. Such an arrangement enables a substantially constant air/fuel mixture strength to be obtained over a wide range of air flow rates in single cylinder engines. Furthermore the supply of mixture to the engine by way of an exit tube 126 may be controlled by a valve member 132 coupled to the engine governor so that the rate of flow of mixture varies in dependence on the load, and additionally so as to change the system between two modes of carburettor operation, namely lean operation, which is provided up to about three quarters load, and rich operation in which additional fuel is supplied to the evaporator 113.

Abstract: The invention is directed to a method and an arrangement for controlling an internal combustion engine wherein the air flow to the engine is influenced at least in component ranges and in a selectable time reference to operations in the engine.

Abstract: A throttle body (10) for use in the air intake system of an internal combustion engine. The throttle body (10) includes a throttle body housing (12) having throttle shaft bearings (22) mounted within it for receiving a throttle shaft (34). The throttle shaft (34) is mounted within the bearings (22) and coupled to a throttle position sensor (26), which is mounted to the throttle body (10). The throttle shaft (34) includes mounting surfaces (40) aligned with the bearings (22) and a sealant (42) applied between the mounting surfaces (40) and the bearings (22) to both seal the intersection between the two and to substantially eliminate axial movement of the throttle shaft (34) relative to the throttle shaft bearings (22).

Abstract: A fuel injection system for an internal combustion engine of a vehicle including a body having a first air channel and a second air channel formed therein, a fuel injection channel formed in the body, a first mixing chamber formed in the body between the fuel injection channel and one of the first and second air channels, a first valve means positioned in the first air channel for limiting a passage of air therethrough relative to movement of an accelerator of the vehicle, a second valve positioned in the fuel injection channel for limiting a passage of fuel relative to a movement of the accelerator, and a third valve positioned in the second air channel for limiting the flow of air/fuel therethrough relative to a movement of accelerator. The first air channel and the second air channel communicate with each other in the body. The first mixing chamber serves to mix fuel from the fuel injection channel with air from the second air channel.

Abstract: A throttle appliances in which induction ducts are configured off-set with respect to the pivoting region of throttle elements, such that metering walls that are provided influence the air throughput at small opening angles of the throttle element in an optimum manner. The throttle appliance is characterized by its extremely accurately matched metering walls in a range of small opening angles of the throttle butterfly in the induction duct. The metering walls are achieved by a method of displacing a rotating chip-cutting element with its center (M) on a previously calculated path (B) in the induction duct in the axial direction with a radial offset. This method permits the manufacture of varied contours of metering walls in order to achieve desired air throughput/opening angle characteristics. The throttle appliance is usually employed in internal combustion engines which are preferably used in motor vehicles.

Abstract: A port throttle valve and an intake system incorporating the valve is disclosed. The valve is disposed between one of two intake runners delivering air to the intake port of an engine cylinder and includes a base member having an opening for delivery of air therethrough. The base includes a track in which is slidingly disposed, two adjacent valve plates each having an opening for registry with the opening in the base member to allow for the passage of air. When moved, in opposite longitudinal directions, the edges of the openings in the valve members move towards one another to terminate registry of the openings with the opening in the valve body.

Abstract: On one side of a valve shaft, there are provided an accelerator drum connected to an accelerator pedal by an accelerator wire, a return spring for urging the accelerator drum in a valve closing direction, and an accelerator sensor for detecting rotation of the accelerator drum and transmitting a detected signal to a host system. On the other side of the valve shaft, there are provided a large-diameter gear and an opening sensor. An armature of a solenoid clutch is attached to the gear and held on a motor shaft via a slide bearing. Thus, the motor, the solenoid clutch and the throttle valve are arranged into a U-shaped form for interconnection through four gears.

Abstract: A novel device of the present invention detects an abnormal driving condition where a sub-throttle valve pressed in a full-opening direction by means of a spring is abruptly driven in the full-opening direction due to an abnormal condition of an actuator, and controls an internal combustion engine according to the requirements. A difference DLTA in an opening TA of a sub-throttle valve 34 within a preset time period is determined (steps S100 through S130) and then compared with a predetermined range allowing to be driven by a stepping motor 32 (step S140). The sub-throttle valve 34 is pressed in a full-opening direction by means of a spring 54. In case of a step-out of the stepping motor 32, the sub-throttle valve 34 is abruptly driven in a full-closing direction by the spring 54. When an abrupt change of the sub-throttle valve 34 is detected, a process under abnormal conditions (abnormality process) including reduction of fuel injection is implemented (step S160).

Abstract: A four-stroke cycle internal combustion engine comprises at least two inlet valves and a correspondingly branched intake line. In order to ensure that a high power and a more favorable specific fuel combustion will be achieved at high speeds and a reduced fuel consumption and a lower emission of exhaust gas will be achieved particularly at low speeds and under partial loads. A rotary valve, which has at least two passages, which are associated with respective intake branch lines and are as straight as possible and lead to respective inlet valves, is provided downstream of the junction where the intake line is branched. The internal combustion engine also comprises at least one additional pipe section, which in one position of the rotary valve is connected by the rotary valve between one intake branch line and one of the passages which is then open whereas the rotary valve then shuts off the other passage or passages.

Abstract: The butterfly valve assembly comprises a body formed with an admission duct and a disk shaped butterfly valve member of predetermined shape carried by a shaft that extends transversally to the passage and mounted for rotation in the body between a minimum opening position of the valve member and a maximum opening position. The duct has a cylindrical length whose cross-section matches with the shape of the butterfly valve member when the latter is in its minimum opening position. It further has respective zones upstream and downstream from the cylindrical length, along the paths followed by upstream and downstream edges of the valve member up to a determined opening angle thereof. Such zones are further defined by successive circular arcs centered on the axis of the admission duct and having radii that decrease going away from the cylindrical length along the axis.

Abstract: A fluid-mechanical variable Venturi metering system having a contoured moveable element in an intake casing to an internal combustion engine whose shape and Venturi air passage(s) results in automatic shifting of the moveable element by aerodynamic force as a function of the mass-volume of the air passing through which with levers produces amplified outputs of displacement, countervailing force and differential air velocity pressure (Venturi vacuum) proportional thereto and compensating for temperature, moisture content and pressure whereby an output or combination of outputs or transducing of outputs applied to fuel control devices and systems provides air-fuel mixtures in optimum ratio for the entire speed-load range of the modern engine for naturally aspirated and supercharged Fuel Injection and Carbureted Injection systems.

Abstract: A pivotable joint including a first part provided with pivot bores and a second part with resiliently mounted pivot pins received in said pivot bores such that the second part is pivotably mounted in a desired assembled position. The first part has a closed tubular cross section and may be a section of the intake manifold of an internal combustion engine. The resiliently mounted pivot pins are symmetrically mounted on opposite sides of the second part, which may be a throttle valve. The pivot pins are elastically displaceable axially during assembly of the first and second parts such that they snap resiliently into the pivot bores of the first part when the second part reaches the desired assembled position.

Abstract: An induction system for an internal combustion engine includes a turbulence-inducing structure, 18, extending across the flow path of a primary runner, 10. The turbulence-inducing structure, 18, is used in combination with a dual or single port intake design.

Abstract: An intake control device for an internal combustion engine having a body member 1 and a throttle valve 5 disposed within an air passage 4 . The external circular edge of the throttle valve 5 is divided, with a throttle shaft 6 into a first edge portion 5a which moves toward the upstream side of the air passage 4 and a second edge portion 5b which moves toward the downstream side of the air passage 4. On an inner wall 7 of the air passage 4 of the body member 1 are formed an upstream-side spherical wall surface 8 in a position facing the first edge portion 5a and a downstream-side spherical wall surface 9 in a position facing the second edge portion 5b.

Abstract: A carburetor assembly having a venturi element for fuel metering and a throttle valve for controlling the flow of an air and natural gas mixture to the combustion chamber of an internal combustion gas engine wherein a stepper motor is used to angularly position a throttle valve plate in the gas flow path to the carburetor, the throttle valve plate being carried on a throttle valve shaft that forms an extension of the armature of the stepper motor wherein provision is made for sealing the stepper motor at a location on the axis of rotation of the throttle valve element, the throttle valve shaft being mounted without the necessity for using throttle valve shaft bearings or a separate seal, thereby minimizing friction and any tendency for a misalignment to occur.

Abstract: An engine control system is disclosed for reducing the hydrocarbon content in the exhaust gas of a crankcase scavenged, two-stroke engine in the operating range near idle, with light operator induced engine loading. As operator demand for engine output power is increased, the system increases the fuel per cylinder supplied to the engine while restricting the supplied mass of air per cylinder to a value less than that flowing at unloaded engine idle.