Abstract: An air-fuel control system for a lean burn engine which carries out lean burning under specific engine operating conditions causes the engine to burn at an stoichiometric air-fuel ratio regardless of engine operating conditions upon an occurrence of malfunctions of a stratifying device and/or a fuel injection timing control device, so as thereby to enable the engine always to operate in good conditions.

Abstract: An improved intake equipment, in which the formation of a liquid fuel film due to deflection of the fuel can be avoided, has a plurality of independent air intake pipes connected to a combustion chamber, for introducing air thereto, collectors connected to the independent air intake pipes, for distributing the introduced air into them, and a throttle valve connected to the collectors, for controlling the amount of air flow. A fuel supplying mechanism is provided on a wall of the independent intake pipes, for supplying fuel to the air and mixing the air and fuel, and a deflection mechanism is provided for deflecting the air flow of the independent intake pipes so as to avoid undesirable deflection of the fuel.

Abstract: A fuel injection system for a multi-valve internal combustion engine that includes an arrangement for controlling the fuel spray in response to engine load and speed. As a result, it is possible to obtain stratification under low-speed, low-load conditions and a homogeneous mixture under high-speed, high-load conditions.

Abstract: An intake port of an engine cylinder is directed so as to introduce intake air flow into a combustion chamber in a desired direction. The intake port has a throat portion, extending upstream from a valve port and configured so as to meet the valve port at a given angle, and a transitional throat portion with a small radius of curvature between the throat portion and the valve port.

Abstract: A cylinder head includes a first intake port for generating a swirl flow in a cylinder and a second intake port for causing a part of intake air to flow into the cylinder in a direction opposite to the swirl flow. The second intake port has a wall at a downstream end thereof, extending below a corresponding intake valve. A portion of the wall adjacent to an exhaust port has a lower or downstream end which is preferably substantially perpendicular to a lower surface of the cylinder head. Accordingly, the intake air flow passing through the second intake port is directed downwardly. Therefore, the swirl flow generated in the cylinder is less likely to be weakened by opposing flows.

Abstract: A number of embodiments of multiple intake valve internal combustion engines that permit the generation of tumble in one direction and at a high velocity under one engine running condition and counter tumble at a lower velocity but in a higher flow volume under other running conditions. The system includes an arrangement for disabling the operation of at least one of the intake passages and for redirecting the flow through another of the intake passages. Embodiments having two, three, and four intake valves per cylinder are disclosed.

Abstract: In a valve operating system for a multi-cylinder internal combustion engine, which is capable of closing and stopping operation of both of a pair of intake valves in a cylinder to provide a stopped state of a cylinder, intake valves are independently operatively connected to first and second driving rocker arms which abut against a pair of stopping portions provided in a completely circular shape without a cam lobe on a cam shaft. A first free rocker arm is provided and abuts against a substantially stopping cam, and a second free rocker arm is provided and abuts against an operating cam. A first connection switch-over device is provided in the first driving rocker arm and the first free rocker arm, and a second connection switch-over device is provided in the second driving rocker arm and the second free rocker arm. A third connection switch-over device is provided in the first driving rocker arm, the second driving rocker arm and the second free rocker arm.

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: Disclosed is a intake air control device for an internal combustion engine, which includes a swirl producing valve provided in the low speed intake tube for partly closing the intake port of the combustion chamber so as to impart swirling motion to the air flowing into the combustion chamber when operating the engine at a low speed including idling, an intake control valve provided in the high speed tube for completely closing the passage of the high speed tube when operating the engine at a low speed including idling.

Abstract: An induction system and combustion chamber configuration for a multiple valve internal combustion engine wherein a tumble action is generated in the combustion chamber about an axis that extends transversely relative to the axis of the cylinder bore and which tumble axis is disposed so as to be substantially at the center of the combustion chamber volume when the piston is at its maximum speed during the compression stroke. This is accomplished by changing the lift, effective flow areas, and/or size of the intake passages.

Abstract: An internal combustion engine includes a valve operating device operatively connected to a pair of intake valves and capable of opening and closing one of the intake valves in accordance with the operating condition of the engine and opening and closing the other intake valve in a small lift amount, thereby producing a deflection of the intake air drawn into the combustion chamber, and a fuel injection valve for injecting a fuel toward the pair of intake valve bores that are independently opened and closed by the intake valves, respectively. The timing of the opening and closing of the intake valve that is opened and closed only in the small lift amount is set at a time point such that the lift amount is maximized in the first half of the intake stroke of the piston. This promotes the atomization of the fuel which is being drawn in with the intake air by the opening of the intake valve opened and closed in the small lift amount, and to enhance the combustibility in the combustion chamber.

Abstract: A cylinder head and induction passage arrangement for a three intake valve internal combustion engine wherein the center intake passage and its porting arrangement is directed so as to augment the tumble action caused by the side valve seats and their intake passages. The construction also provides that the center intake valve will be disposed so that there will be no shrouded area in the path of flame from the spark plug so as to ensure complete combustion. The cylinder head is made in such a way that the same cylinder head may be used for either bank of an engine having angularly inclined cylinder banks through the machining of only one face thereof.

Abstract: A preferred combustion chamber configuration for a piston engine includes two intake valves and one exhaust valve. The two identical intake valves and their associated induction system are arranged to promote separation of the two barrel swirl layers as established in the engine cylinder through the two valves. Further included, in a location containing the intake valves, is a large squish area for providing a fast burn rate in spite of spark ignition in just the richer one of the two barrel swirl layers. Such ignition therefore remains reliable and consistent even when no fuel is injected into the intake passage feeding the leaner swirl layer. Also included in the invention is an engine operating strategy which refrains from injecting fuel into the leaner intake passage until a central engine throttle valve is first at least effectively wide open. Drive-by-wire control coordinates the resulting throttled and unthrottled ranges of engine brake torque output.

Abstract: Control arrangements for the induction system of an internal combustion engine having a control valve in the induction passage which is moveable between an opened position wherein the flow into the combustion chamber is unrestricted and in a first direction and in closed position wherein the flow into the combustion chamber is restricted to accelerate the velocity of the charge entering the combustion chamber and change its direction from the first direction. Optimum positions are set for the control valve in response to engine speed and engine load but the control valve is held in a closed position when the engine speed is below a predetermined speed and regardless of the load and is also held in an opened position when the engine speed is above a second predetermined speed and regardless of load. Various routines are shown for positioning the control valve to accommodate catalytic convertor warm up, sudden acceleration or deceleration conditions and other transient conditions.

Abstract: Disclosed is an apparatus for generating a tumble in a cylinder of a fuel injection engine in order to improve combustion. The apparatus comprises an air intake passage having a straight portion whose center line is approximately in parallel with a roof face of the combustion chamber on the exhaust valve side and a tumble control valve for generating a tumble in the cylinder. The tumble control valve is a flap valve or a butterfly valve for closing a second air intake passage and for opening a first air intake passage.

Abstract: A cylinder head and induction passage arrangement for a three intake valve per cylinder internal combustion engine that provides a compact configuration while at the same time maintaining an induction system that is tuned to provide optimum performance throughout the entire engine speed and load ranges. In addition, the intake passages and associated control valves for them are arranged so as to generate a tumble action in the combustion chamber under low and mid-range performance while permitting maximum charging under high speed, high load conditions. A single fuel injector injects fuel in such a way as to serve at least a pair of the intake passages.

Abstract: A number of embodiments of induction system for internal combustion engines employing multiple intake valves. The induction systems are designed so as to provide substantially unrestricted charging and axial flow into the cylinder bore when running under high-speed, high-load conditions. A control valve is provided which changes the effective configuration of the induction passages so as to provide a slant tumble action under lower speed and load conditions. Various arrangements are disclosed for altering the amount of slant action and providing slant actions in opposite or the same direction. In addition, a single control valve element is provided for achieving this effect in a three poppet valve per cylinder engine.

Abstract: An engine air intake system comprises a main air duct and at least one bypass air duct, which are located side by side. The bypass air duct is smaller in cross-sectional area than the main air duct which is provided with a throttle contiguous to the bypass air duct having therein a control valve. The throttle and the control valve are regulated by a link mechanism such that the throttle is closed when the engine is operating at a low or intermediate load rate, and that the control valve is opened partially when the throttle remains closed, thereby resulting in an acceleration of air current flowing through the bypass air duct and an improvement in the tumble or swirl ratio. As the engine is operating at a progressively increasing load rate, the throttle is caused to open gradually to bring about an increase in the engine air intake volume so as to enable the engine to operate under the optimum condition.

Abstract: A number of embodiments of multi-valve twin overhead cam internal combustion engines having direct fuel injection and spark plugs that are disposed between the camshafts and generally centrally of the combustion chamber. Various orientations are disclosed, and in all disclosed embodiments, twin spark plugs are employed.

Abstract: Control arrangements for the induction system of an internal combustion engine having a control valve in the induction passage which is moveable between an opened position wherein the flow into the combustion chamber is unrestricted and in a first direction and in closed position wherein the flow into the combustion chamber is restricted to accelerate the velocity of the charge entering the combustion chamber and change its direction from the first direction. Optimum positions are set for the control valve in response to engine speed and engine load but the control valve is held in a closed position when the engine speed is below a predetermined speed and regardless of the load and is also held in an opened position when the engine speed is above a second predetermined speed and regardless of load. Various routines are shown for positioning the control valve to accommodate catalytic convertor warm up, sudden acceleration or deceleration conditions and other transient conditions.

Abstract: A number of embodiments of induction system for internal combustion engines employing multiple intake valves. The induction systems are designed so as to provide substantially unrestricted charging and axial flow into the cylinder bore when running under high-speed, high-load conditions. A control valve is provided which changes the effective configuration of the induction passages so as to provide a slant tumble action under lower speed and load conditions. Various arrangements are disclosed for altering the amount of slant action and providing slant actions in opposite or the same direction. In addition, a single control valve element is provided for achieving this effect in a three poppet valve per cylinder engine.

Abstract: The engine has first and second intake ports for one cylinder (combustion chamber). The intake ports are formed in a cylinder head and extend substantially parallel to each other. Downstream ends of the first and second ports open to a combustion chamber defined in the cylinder upon a compression stroke. The first intake port is a helical port to generate and supply a first swirl into the combustion chamber. The second intake port has a recess in its wall near its downstream end to reverse the flow direction of the air in the second intake port so as to generate and supply a second swirl into the combustion chamber. The recess in the second intake port reverses the air flow direction before the intake air in the second intake port enters the combustion chamber, so that the second swirl flows in the same direction as the first swirl in the combustion chamber. Therefore, a single strong swirl is obtained in the combustion chamber.

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: An intake system for an internal combustion engine includes first and second intake valve bores provided to face a combustion chamber and to be independently opened and closed by first and second intake valves, and first and second intake ports which are connected to the corresponding intake valve bores with a partition wall interposed therebetween and which communicate with a common intake passage. In a particular operation range of the engine, an imbalance is produced in the concentration of the air-fuel mixture flowing through the first and second intake valve bores into the combustion chamber on the basis of a difference between the amounts of fresh air flowing into the first and second intake ports. The intake system further includes a communication hole provided in the partition wall for putting the first and second intake ports into communication with each other. This provides for improvements in the lean combustibility and in the nature of the exhaust gas.

Abstract: A camshaft supported in an engine cylinder head structure has a low speed (lift) cam lobe and a high speed (lift) cam lobe. A rocker arm is supported by a hydraulic lash adjuster or a rocker shaft for pivotal motion and has a sub-rocker shaft and a pin. The rocker arm is drivingly engages the low lift cam lobe. A free cam follower is supported by the sub-rocker shaft and drivingly engages the high lift cam lobe. A latch lever supported by the pin has a latch position wherein one end portion of the latch lever is in locking engagement with the free cam follower and a latch release position wherein the one end portion of the latch lever is out of engagement with the free cam follower. A hydraulic piston received in bore is in driving engagement with the opposite end portion of the latch lever to urge the latch lever against a latch lever release spring towards the latch position thereof.

Abstract: A pushrod-operated-valve-in-head six cylinder engine has two intake valves per cylinder. Five of the seven air intake runners in the cylinder head are arranged so that at least one intake valve port of each cylinder adjacent to another cylinder shares an intake runner with an intake valve port of the adjacent cylinder. Each of the shared runners feeds one valve port of each of two adjacent cylinders. The firing order of the engine is such that intake strokes for the adjacent cylinders are separated in time. Therefore, only one of the sharing cylinders at a time is supplied with air by the shared runner. In addition, because each runner is supplying only one valve per cylinder, there are two runners feeding each cylinder. For each cylinder, one port is the tangential type, and the other is the helical type. In one embodiment, the valve port connections to the shared runners are arranged for variable swirl production, by pairing the same style intake ports on each runner e.g.

Abstract: A number of embodiments of valve actuating mechanisms for four-cycle engines including a camshaft and a rocker arm actuated by the camshaft for operating an associated poppet valve. The camshaft and rocker arm followers are configured so as to provide an increasing lever ratio on valve opening for effective rapid valve opening and a decreased lever ratio on valve closing so as to avoid valve bounce. Various arrangements of camshafts and rocker arm positions are disclosed.

Abstract: A stratified burning internal combustion engine according to this invention is equipped with an intake port and a fuel feed device so that stratified tumble flows of different fuel concentrations can be formed in a combustion chamber. An ignition device is provided in the combustion chamber to ignite at least one of the tumble flows, said at least one tumble flow being rich in fuel. To promote the stratified tumble flows, a top wall of a piston has an inclined wall. This makes it possible to strengthen the tumble flows, whereby the stratification of an air-fuel mixture in the combustion chamber can be improved further to permit lean burn at a larger air/fuel ratio.

Abstract: A cylinder head of an internal-combustion engine has three intake valves on one side of a longitudinal center plane and has two exhaust valves on the other side. The intake valves are arranged in a circumferential direction of a cylinder of the internal-combustion engine, and a first intake valve arranged close to the edge of a combustion chamber is permanently driven by a camshaft by means of a space-saving actuating lever. The other intake valves are connected successively or isochronously according to the requirements. When the load is low, a fuel-saying load movement is achieved by the tangential inflow through the first intake valve, while, when the load requirements are higher, an optimized mixture flow rate is possible via the connected valves.

Abstract: An engine intake system includes a primary port for introducing intake gas throughout an entire engine operating condition. A secondary port is provided with a gate valve which is opened in a high engine load condition for introducing the intake gas. A ratio of a tumble flow to a swirl flow is gradually increased as the gate valve is operated from an entirely closed condition to a fully open condition. According to this invention, ignition and combustion characteristics can be improved.

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: A cylinder head for an international combustion engine comprises at least two separate intake ports with each incorporate one intake valve and at least one exhaust port, which in turn incorporates one exhaust valve, where the intake ports and the exhaust port have their openings on opposite lateral faces of the cylinder head. The cylinder head also comprises a centrally arranged fuel injector which is driven by a top rocker arm, a push rod passing through the cylinder head, and a bottom camshaft. The cylinder head is also designed with a common vertical shaft or through hole which incorporates push rods for transferring the drive from the camshaft to the valves and to the fuel injector. The shaft is arranged between the two intake ports.

Abstract: A number of embodiments of induction systems for internal combustion engines wherein a control valve arrangement is provided in the induction passage for selectively generating either or both of tumble and/or swirl to the intake charge in response to varying running conditions. Various types of control valve arrangements are disclosed as are systems for cooling the control valves and augmenting the flow pattern caused by the control valve.

Abstract: An engine comprising a first intake valve and a second intake valve that are arranged on each side of a plane including the axis of the cylinder of the engine. A first intake passage and a second intake passage are connected to the combustion chamber via the first intake valve and the second intake valve, respectively and extend along the plane in the same direction. A first fuel injector is arranged in the combustion chamber to inject fuel toward a region of the combustion chamber, which is located on the first intake valve side of the plane. A second fuel injector is arranged in the second intake passage to inject fuel into the second intake passage.

Abstract: A combustion chamber for an engine is provided between a cylinder bore formed in a cylinder block, a generally conically-shaped wall formed in an under wall of a cylinder head, and a piston in the cylinder bore. The combustion chamber has a structure into which an intake port opens so as to introduce an intake air flow closer to a marginal portion than a central portion of the combustion chamber, thereby generating a swirl flow of intake air in the combustion chamber. The combustion chamber also includes a curved air flow guide wall formed in the generally conically-shaped wall which extends from near the intake port so as to approach the cylinder bore surface gradually, thereby generating what is termed a squish flow of intake air.

Abstract: An air intake arrangement for an internal combustion engine comprising: a main air intake conduit leading to a gas intake valve (241 ) for respective engine cylinders (206 ) and including a main air intake passage (202 ), a main collector chamber (204 ) and independent branching air intake passages (205) for the respective engine cylinders (206) connected in series; a throttle valve (203 ) disposed in the main intake air passage (202 ) for controlling the flow rate of air passing therethrough; an auxiliary air intake passage (210 ) bypassing the main air intake conduit, an inlet port of the auxiliary air intake passage (210 ) opens into the main air intake passage (202) at the upstream of the throttle valve (203 ), an outlet port (213 ) of the auxiliary air intake passage (210 ) opens into the respective independent branching air intake passages (205) near the gas intake valve (241) for the respective engine cylinders (206 ) in such a manner that gas blown-out from the auxiliary air intake passage (210 ) indu

Abstract: Several embodiments of induction systems for internal combustion engines wherein the effective shape of the intake passage may be changed during engine running conditions to achieve turbulence of the desired type in the combustion chamber and improve volumetric efficiency at low and mid range performance and provide a substantially uninterrupted introduction of charge under high speed running so as to improve the performance throughout the entire engine load and speed ranges. Also, a control valve arrangement is provided in the exhaust system for improving performance under low engine speeds and low engine loads.

Abstract: On a main rocker arm, there is arranged a pivotal sub-rocker arm. A rocker arm coupling mechanism is employed which, under a given condition of an associated engine, couples tightly the main rocker arm and the sub-rocker arm to cause the main rocker arm to pivot in accordance with rotation of a higher lift cam. First and second tappet members are carried by the main rocker arm to actuate two intake or exhaust valves of the engine in response to the pivoting movement of the main rocker arm. The second tappet member is loosely connected to the main rocker arm so that, under a certain condition, the second tappet member fails to transmit the pivoting movement of the main rocker arm to the associated valve. A tappet locking mechanism is further employed which, under a given operation condition of the engine, locks the second tappet member to the main rocker arm thereby to ensure the transmission of the pivoting movement of the main rocker arm to the associated valve.

Abstract: An internal combustion engine according to this invention is provided with intake ports and an injector. The intake ports are designed to form stratified tumble flows of different fuel concentrations in a combustion chamber. A spark plug is arranged in the combustion chamber to ignite one of the tumble flows, which one tumble flow is rich in fuel. Each intake port is provided with a longitudinal partition which divides an interior of the intake port into two passages. These longitudinal partitions are formed in such a way that, of the air-fuel tumble flows formed around the spark plug, the tumble flow closest to the spark plug is formed of a richer air-fuel mixture. Each longitudinal partition is arranged only on a side upstream of a valve stem of an intake valve in the corresponding intake port, so that a sufficient amount of intake air can be obtained while extremely minimizing a reduction in the actual cross-sectional flow area.

Abstract: An engine comprising a first intake valve and a second intake valve that are arranged on each side of a plane including the axis of the cylinder of the engine. A first intake passage and a second intake passage are connected to the combustion chamber via the first intake valve and the second intake valve, respectively and extend along the plane in the same direction. A first fuel injector is arranged in the combustion chamber to inject fuel toward a region of the combustion chamber, which is located on the first intake valve side of the plane. A second fuel injector is arranged in the second intake passage to inject fuel into the second intake passage.

Abstract: A stratified charge burning internal combustion engine with a fuel injection time controlling function wherein production of smoke upon high load operation of the engine can be reduced by control of the fuel injection time. Fuel injection time setting means sets a fuel injection end time and further sets a fuel injection start time from the fuel injection end time and a required fuel amount, and injector driving means drives an injector in accordance with the fuel injection times. Consequently, air fuel mixture and air from a pair of intake ports are flowed into the combustion chamber to make laminar tumble swirls so as to effect laminar combustion.

Abstract: An intake system for a multiple-cylinder engine a plurality of primary discrete intake passages and a plurality of secondary discrete intake passages. Each pair of primary discrete intake passage and the secondary discrete intake passage communicate with one of the cylinders. Both the primary and secondary discrete intake passages are straight and the primary discrete intake passage is provided with a primary valve member which is provided with an opening and is selectively positioned in a closed position where the primary valve member limits the effective cross-sectional area of the primary discrete intake passage to the cross-sectional area of the opening and in an open position where the primary valve member wide opens the primary intake passage.

Abstract: A four-stroke cycle internal-combustion engine having two large- and small-diameter intake valves and two large- and small-diameter exhaust valves in one cylinder and mounted with a valve-operating mechanism on either of the intake valve side and the exhaust valve side. Each valve-operating mechanism comprises a first valve-operating cam of a narrow total valve-opening angle and a low lift, a second valve-operating cam of a wide total valve-opening angle and a high lift, a rocker arm for the small-diameter valve in direct engagement with the first valve-operating cam, a rocker arm for the large-diameter valve, and a connecting means capable of simultaneously operatively connecting the second valve-operating cam with the rocker arm for the small-diameter valve and the rocker arm for the large-diameter valve. In each cylinder at least three spark plugs are mounted. The combustion chamber is formed high on one side and low on the other side.

Abstract: An intake air control device including a reed valve passage for supplying intake air via reed valves, and a sub intake passage for creating a swirl in the combustion chamber. The intake air control device further comprises a main intake passage for supplying intake air without passing same through the reed valves. A selection unit selects a passage through which the intake air is passed in response to a current engine driving condition, by selecting the sub intake passage when the current engine driving condition is a low engine speed and low engine load driving condition, selecting the reed valve passage when the current engine driving condition is a low engine speed and high engine load driving condition, and selecting the main intake passage when the current engine driving condition is a high engine speed driving condition.

Abstract: A number of embodiments of intake passages for internal combustion engines wherein it is possible to obtain a tumble and tumble and swirl action or both under some running conditions and substantially unrestricted flow under high speed conditions so as to improve volumetric efficiency while, at the same time, increasing turbulence under the conditions when the flow pattern is altered. The flow pattern is controlled by a rectifier plate which extends through at least one of the intake passages and divides it into two flow areas, one of which is closed by a control valve which engages the rectifier plate in its flow controlling position so as to provide a stop for the control valve. The control valve is configured and oriented so as to provide substantially unrestricted flow paths in each of its positions. Embodiments incorporating carbureted and fuel injected engines are depicted.

Abstract: An adjustable valve gear is provided for two lift-type intake valves per cylinder in an internal combustion engine which are actuated by the cams of a camshaft via rocker arms with variable support and a rocker cam. In order to make possible different lift curves for the two lift-type intake valves, each lift type intake valve is assigned a separate rocker cam. At least one of the curve joints assigned to a lift-type intake valve and establishing the connections between a cam and a rocker arm, between the rocker arm and its support and between a rocker cam and the lift-type intake valve are configured with a different shape or a rotated installation position relative to a curve joint assigned to the other lift-type intake valve.

Abstract: This invention relates to an intake port structure for an internal combustion engine. It is an object of the present invention to increase the strength of tumbling without lowering the maximum flow rate. An intake port (44) is constructed broader in a tumble-flow-side half (44a) than in the other half (44b) to have an intake air flow through the intake port (44) off-centered toward the side of a tumble flow, whereby an intake air flow from the intake port (44) promotes the tumble flow.

Abstract: A mechanical supercharger is provided in an intake manifold, and two inlet ports in communication with a cylinder are provided. A swirl control valve disposed in one of the two inlet ports is opened in a low speed/medium load region, and closed in a low speed/high load region and a low speed/low load region. Accordingly, scavenging performance can be enhanced in the low speed/medium load region where the pressure of a supercharged mixture flow is not sufficiently higher than the pressure of exhaust gas. In the low speed/high load region where the pressure of the supercharged mixture flow is sufficiently higher than the pressure of exhaust gas, undesired blowing of the mixture through a combustion chamber without being used for combustion can be suppressed while ensuring satisfactory scavenging, and an occurrence of knocking can be prevented.

Abstract: An engine comprising a fuel injector arranged on the inner wall of the cylinder in the vicinity of the intake valve. When the engine is operating under a heavy load, fuel is injected by the fuel injector during the intake stroke toward the rear face of the valve head of the intake valve. At this time, the injected fuel impinges upon the rear face of the valve head of the intake valve and is reflected thereon. Then, the injected fuel flows into the intake port.

Abstract: An engine control system for controlling an internal combustion engine equipped with a mechanical supercharger includes a valve timing control mechanism which causes first and second intake valves for each cylinder to retard opening and closing of a first intake port with respect to opening and closing of a second intake port. Opening and closing of the first intake port is retarded when a specific range of engine operating conditions, in which the supercharger is operating, is detected.