Abstract: An improved induction system for a V type engine that is tuned for substantially all running conditions and which is nevertheless compact in construction. The system includes a pair of air boxes each disposed adjacent one of the cylinder heads of the engine. Each cylinder head has at least two intake passages serving the respective cylinder bores and a first conduit extends from the adjacent air box to one of the intake passages and a second conduit extends from the other of the air boxes to the other intake passage. A throttle valve arrangement is also incorporated so that good performance is achieved under all running conditions.

Abstract: A variable swirl siamese type intake port structure for an internal combustion engine cylinder head includes a first generally straight intake passage which leads to a first intake port and a second generally helical intake passage which leads to a second intake port which is formed with a helical end vortex portion. A control valve is fitted in the first generally straight intake passage at an upstream portion thereof so as to control its flow resistance. A bypass passage opens from a point downstream of the control valve in the first generally straight intake passage to the helical end vortex portion of the second intake port. And a downstream portion of the bypass passage is communicated to a downstream portion of the second generally helical intake passage. Thereby the resistance to flow of air-fuel mixture of the generally helical intake passage is diminished, and the engine volumetric efficiency and the maximum attainable engine output power are increased.

Abstract: An intake air control device for an internal combustion engine having a battery, an electrically operated fuel pump, a fuel injector, an intake air flow control means operative in response to the running condition of the engine, and an operating means for operating the air flow control means. The device further comprises a detecting means for detecting the voltage of the battery, and a control means for controlling the operating means for the intake air flow control means such that the amount of the intake air is decreased when the detected voltage is lower than a predetermined value.

Abstract: An induction system for an internal combustion engine for improving running throughout the entire engine speed and load ranges. The induction system comprises a first intake passage that serves the chamber through a first intake port and a second intake passage that serves the chamber through second and third intake ports. The effective cross-sectional area of the first intake passage is substantially smaller than that of the second intake passage and staged throttle valves are incorporated so that the charge requirements at low speed are supplied primarily through the first intake passage.

Abstract: Engines having cylinders of noncircular cross section wherein the cylindrical curve is generated at a preselected constant outwardly normal distance from a closed curve. The closed curve is defined as including two spaced points on a major axis of symmetry of the cylinder with two continuously curved portions extending between these points and curved outwardly from the major axis. The closed curve about which the cylinder curve is generated is preferred such that there is a continuous change of curvature without discontinuity in that curvature in the cylindrical curve. The avoidance of discontinuity in the generating curve aids in mass production consideration and cutter life. A plurality of intake and exhaust port arrangements are disclosed illustrating four intake ports and four exhaust ports on opposite sides of the major axis of symmetry of the defined cylinder. In one embodiment, the outermost of the ports are smaller and are positioned closer to the major axis of symmetry.

Abstract: An injection system for an internal-combustion engine has a plurality of separate inlet ports provided for each cylinder of the engine, and an intake pipe encompassing the inlet ports for each cylinder. The intake pipe has a subdividing web wall in the region of the cylinder head having a mixing chamber into which fuel is injected by an injection nozzle. The subdividing web wall subdivides the intake pipe into separate intake pipe sections and includes shot channels for communicating fuel from the mixing chamber to each of the separate intake pipe sections. By this arrangement, a constant, thorough mixing of the fuel/air mixture is achieved even at lower load and upper speed ranges of the engine.

Abstract: A variable swirl siamese type intake port structure for an internal combustion engine cylinder head includes a first generally straight intake passage which leads to a first intake port and a second generally helical intake passage which leads to a second intake port which is formed with a helical end vortex portion. A control valve is fitted in the first generally straight intake passage at an upstream portion thereof so as to control its flow resistance. A substantially straight auxiliary passage, opening from a point upstream of the control valve to a point near the downstream end of the first intake port and bypassing the control valve, points through the first intake port, when open, generally at the ignition point of the engine spark plug. Thereby, when the control valve is closed, even then an air-fuel mixture stream is directed straight at the spark plug, and this prevents local weakening of mixture due to centrifugal effects.

Abstract: An internal combustion engine comprising three intake valves. The first intake valve and the second intake valve open at a crank angle near to the top dead center of the intake stroke. The third intake valve opens approximately at the center of the intake stroke. An air control valve is arranged in the second intake passage connected to the combustion chamber via the second intake valve. The air control valve is closed when the engine is operating under a partial load. A fuel injector is arranged in the third intake passage connected to the combustion chamber via the third intake valve. The injecting operation of the fuel injector is stopped during the intake stroke.

Abstract: An induction system for an internal combustion engine that improves mid range torque without sacrificing low speed running or high speed performance. Each cylinder of the engine is served by two intake ports that are, in turn, served by respective intake passages that have a common portion. A first throttle valve is positioned in the common portion for precluding the back flow of exhaust gases and for controlling the flow to the chamber. In addition, first and second inlet passages discharge into the common intake passage and a throttle valve is positioned in one of those inlet passages.

Abstract: Several embodiments of cylinder head and valve train configurations for an overhead valve internal combustion engine that permits increased valve area without interference and while maintaining simplified valve actuation. In each embodiment one pair of valves is operated by one cam shaft and lies on one side of a plane containing the axis of the cylinder. Three other valves are positioned primarily on the other side of the plane and reciprocate about axes that are not parallel with each other. These axes, however, intersect so that each of these three valves may be operated by the same cam shaft. In one embodiment of the invention the intersection of the valves axis is coincident with the axis of rotation of the respective cam shaft so as to permit direct actuation of the valves. In another embodiment the intersection lies substantially along a plane that intersects the stems of the valves when they are closed to facilitate operation of multiple valves from a single cam lobe by means of a single rocker arm.

Abstract: A four cycle internal combustion engine has a cylinder, a piston slidable therein, intake and exhaust valves, a pair of intake passages, and an exhaust passage. There are at least three intake valves, and the intake passages are connected so that each discharges to an intake valve adjacent to the central axis of the cylinder, and in addition also to respective other intake valves on the opposite sides of an axis of symmetry. The plural intake valves, and if desired also the plural exhaust valves, are simultaneously activated because they are connected to a respective plate that is contacted by an actuating cam. The respective valve stems are inclined in a V shaped configuration to accommodate a plug between them, and a central one of the valves can be offset (advanced) into the combustion chamber to improve the combustion characteristics.

Abstract: A combustion chamber configuration for an engine having three intake valves and two exhaust valves per cylinder. The combustion chamber configuration permits the use of stroke-to-bore ratios of 0.8 to 1 or less and compression ratios of 9 to 1 or greater while affording good flame travel in the combustion chamber. The piston is formed with a generally flat head that has semi-circular recesses for valve clearance.

Abstract: In an internal combustion engine having a pair of intake valves, the valve driving system for timing the intake valves is provided with a valve timing changing mechanism for changing the timing of at least one of the intake valves. The valve timing changing mechanism retards or advances the timing of said one intake valve to change the total intake valve opening time, i.e., the time that at least one of the intake valves is open, according to the operating condition of the engine.

Abstract: An improved induction system for a V type engine that is tuned for substantially all running conditions and which is nevertheless compact in construction. The system includes a pair of air boxes each disposed adjacent one of the cylinder heads of the engine. Each cylinder head has at least two intake passages serving the respective cylinder bores and a first conduit extends from the adjacent air box to one of the intake passages and a second conduit extends from the other of the air boxes to the other intake passage. A throttle valve arrangement is also incorporated so that good performance is achieved under all running conditions.

Abstract: Combustion engine having a cylinder and a piston movable therein and having a spark plug for igniting the combustible fuel. Three valves are concentricly located coaxially with the spark plug for separately controlling the flow of incoming fresh air to the cylinder and the flow of the fuel mixture to the cylinder and the flow of the exhaust gases from the cylinder. The engine presents the necessary valve seat for the exhaust valve, and the other two valves are also provided with valve seats, and springs urge each of the valves toward their respective seated positions. Also, push rods and rocker arms are arranged for opening the valves, as required. The entire arrangement provides for introducing a layer of clean air next to the cylinder wall and then introducing the fuel mixture into the center of the cylinder and adjacent the spark plug. Upon firing, the flame is primarily confined by the boundary of fresh air, and the flame is thus away from the cylinder wall.

Abstract: The combustion, especially a lean mixture, in an internal combustion engine is improved by providing an additional air introducing device. The device comprises an air by-pass pipe introducing additional air independently from the airflow through an intake manifold and having its outlet in the manifold at the vicinity of an intake valve and an air by-pass valve for adjusting the flow rate of the additional air through the by-pass pipe according to operational conductions of the engine. As a consequence, during the suction stroke of a cylinder, additional air, stagnated in the vicinity of the intake valve, is at first drawn in and then an air-fuel mixture supplied by a fuel injector is supplied to the cylinder. Accordingly, the stratification of combustible fluid is performed within the cylinder, in which an ignition plug is exposed to an upper phase formed by the mixture.

Abstract: An inlet system for an internal combustion engine comprises a plurality of auxiliary inlet passageways which curve and extend outwardly of a plurality of mating main inlet passageways and joining with the main inlet passageways, respectively, at an acute angle at their downstream portions.

Abstract: An engine intake system including a primary and secondary intake passages which are separated from each other and are respectively provided with a primary and a secondary fuel injection valve. The secondary intake passage is closed and the secondary fuel injection valve is inoperable for light load engine operation. When the secondary fuel injection valve is restarted to operate for heavy load engine operation, the quantity of fuel supply is momentarily increased to avoid any stepwise change in the engine output torque. The amount of the increase in the fuel supply is increased in response to a decrease in the engine speed. When operation of the secondary fuel injection valve is stopped, the fuel supply is decreased.

Abstract: A supercharged engine having a supercharger which is operated only when the engine load is greater than a predetermined value. An ignition timing control device is provided for determining a basic ignition timing in accordance with the engine operating condition. The basic ignition timing is retarded by a predetermined value when a supercharging signal is produced for commencing the supercharging, and is gradually advanced to the basic ignition timing in a predetermined time period.

Abstract: Two embodiments of overhead camshaft internal combustion engines that provide a compact arrangement through a simplified bearing and thrust arrangement for the camshafts. In accordance with each embodiment, one of the lobes of the camshafts are positioned at the ends of the camshafts and the camshafts are axially located by thrust surfaces formed between pairs of lobes. In one embodiment of the invention, the camshaft operates three valves per cylinder. In this embodiment, the fastening means for affixing the cylinder head to the cylinder block lies beneath the camshafts and the camshafts have openings so that the fastening means may be tightened without necessitating removal of the camshafts.

Abstract: An improved induction system for a V type engine that improves both charging and combustion efficiency. The engine includes an induction system for each cylinder barrel that includes a pair of intake valves and respective intake passages that have a common inlet. One of the intake passages is curved and an auxiliary intake passage extends through the cylinder head and terminates at an auxiliary intake port that is disposed at one side of the main intake port in proximity to the cylinder barrel for generating a swirl to the intake charge. A plenum chamber is positioned in the V of the engine and defines two separate chambers each of which communicates with a respective one of the auxiliary intake passages.

Abstract: In order to prevent large amounts of residual gas from remaining in the combustion chamber after the exhaust phase in an engine provided with dual induction arrangement including two inlet valves and corresponding induction ports, air is bled into the port which closed off by a flow control valve during low speed operation so as to obviate the vacuum which tends to develop therein and induct exhaust gas during the exhaust phase.

Abstract: An induction system for an internal combustion engine wherein each chamber of the engine is provided with three intake ports and one charge former serves two of those intake ports while another charge former serves the other intake port. The charge formers employ a staged throttle valve arrangement so that the other charge former supplies the idle and low speed requirements and the first mentioned charge former comes into operation only at high speeds and loads. In accordance with another feature, the arrangement is provided for pairs of chambers and the single charge former serves two chambers.

Abstract: An embodiment of an induction system for internal combustion engines that permits maximum power output while at the same time insuring good running at low speeds without loss in mid-range torque. Independent intake passages communicate with each chamber of the engine. A throttle valve arrangement is included that includes a first manually operated throttle valve positioned in a common portion of the intake passages, a second manually operated throttle valve that is positioned in the first intake passage between the first throttle valve and the chamber, and a third throttle valve positioned in the second intake passage between the first throttle valve and the chamber. A linkage system interconnects the first and second throttle valves so that the second throttle valve is opened at a predetermined degree of opening of the first throttle valve. The linkage causes the first and second throttle valves to reach their fully opened position simultaneously.

Abstract: An engine valve train system for selectively effecting operation of a pair of side by side valves of a cylinder and to effect deactivation of one of the valves in the pair during predetermined modes of engine operation includes first and second rocker arms pivotably supported on a hollow rocker shaft which in turn is suitably supported for pivotable movement between an operative position and an idle or inoperative position and which is connected to a source of pressurized hydraulic fluid. The first rocker arm is adapted to be driven by an actuator to effect opening and closing movement of one of the valves.

Abstract: An intake arrangement for an internal combustion engine, including a plurality of intake ports opening into a combustion chamber, a plurality of intake valves for opening and closing the intake ports, respectively, a main intake passage having a plurality of branch intake passages connected to the intake ports, respectively, a shutter valve for opening and closing the main intake passage, and an auxiliary intake passage branched from the main intake passage and connected to one of the intake ports.

Abstract: An internal combustion engine in which a stream of air from a duct (46) to a cylinder (2) so as to flow adjacent to the cylinder walls. The duct (46) is arranged to admit the air only while the exhaust valve (42) is open. The air will circulate against the cylinder walls during the exhaust stroke but at least a portion thereof will remain adjacent the cylinder walls during the subsequent compression stroke. The combustible charge is admitted generally centrally of cylinder and remains stratified with respect to the circulating air. The circulating air maintains the combustible mixture relatively concentrated for good ignition, cushions the igniting gases, assists in maintaining the cylinder walls clean and cools the exhaust valve.

Abstract: A porting and valve arrangement for an internal combustion engine embodying three valves serving the same chamber. Separate passages extend from each of the valves and merge into a common symmetrical portion for facilitating good distribution and cooperation with an associated manifold or the like.

Abstract: The two inlet pipes and the exhaust pipe (6) open onto the same lateral wall (7) of the cylinder-head, the exhaust pipe opening onto this lateral wall at a level between the level of the inlet pipes and the level of the surface of the cylinder-head in contact with the cylinder-block (2). The other side (8) of the cylinder-head is in this way free to receive a precombustion chamber (9) and the timing gear can be constructed with a single overhead cam-shaft (12).

Abstract: A hollow drum-like surge tank is supported for rotation in a casing. The surge tank communicates with the atmosphere by way of an opening formed in one end thereof and with the interior space of the casing by way of communicating holes formed in the peripheral surface of the surge tank. Intake pipes curl downwardly from intake ports of an engine and communicate with the internal space of the casing, whereby intake passages for the engine are formed through the surge tank, the interior space of the casing and the intake pipes. The surge tank is rotated back and forth about the longitudinal axis thereof, the amount of rotation depending on the engine speed, so that the distance between the communicating holes and the position in which the intake pipes communicate with the interior space of the casing is changed according to the engine speed, thereby changing the effective lengths of the intake passages for the engine according to the engine speed.

Abstract: An intake system of an internal combustion engine is provided with a cross-sectional area changing means and a length changing means so that the cross-sectional area and/or the length of the intake system may be changed according to the change in the engine speed. Basically, at a high engine speed, the cross-sectional area is enlarged and the length is also enlarged to obtain an inertia supercharging effect at the high engine speed. By making the timing of changing the area different from that of changing the length, it is possible to maximize the inertia supercharging effect over a wide range of engine speeds. The cross-sectional area may be changed from SMALL to LARGE before the length is changed from LONG to SHORT, or after the length is changed from LONG to SHORT. The length may be changed stepwisely or continuously.

Abstract: Several embodiments of induction systems for internal combustion engines embodying three intake valves per cylinder. Each system divides the induction passage for each cylinder into at least two parts and a flow controlling throttle valve is positioned in one of the parts. In some embodiments, the parts have equal effective flow areas and in others they have unequal flow areas. In further embodiments, there are three intake passages serving the same chamber and throttle valves are positioned in two if them. In some of these embodiments, the throttle valves are operated simultaneously while in others they are operated in staged sequence.

Abstract: An engine intake system having primary and secondary intake passages leading to the same combustion chamber. The secondary intake passage is provided with an auxiliary throttle valve which is opened under a relatively high load engine operation. The primary and secondary intake passages are respectively provided with first and second fuel injection valves which are controlled by an electronic control unit in accordance with engine operating conditions. The electronic control unit functions to determine a basic fuel supply quantity based on the intake airflow and the engine speed and modify the basic quantity by a compensation factor which is obtained from a compensation map. The compensation map is divided into two zones, the first zone substantially corresponding to the engine operating condition wherein the auxiliary throttle is closed, the second zone substantially corresponding to the engine operating condition wherein the auxiliary throttle valve is opened.

Abstract: Each combustion chamber of the engine is communicated with (a) first and second induction passages which are dimensioned to produce an optimal ramming effect during high speed and (b) a third passage which provides good ramming during low engine speed operation. The first and second induction passages are provided with flow control valves which can be opened simultaneously or in a step-wise manner as the engine speed moves from a low speed range into a high speed one. The third passage is arranged to merge with the first so that during idling and the like, the flow of air therefrom enters the combustion chamber in a manner which produces a strong swirl and promotes good atomization of the fuel injected into the first passage by a fuel injector.

Abstract: In a reciprocating piston internal combustion engine, an upwardly arcuately shaped combustion space is formed in the cylinder head, which contains suspended valves arranged V-shaped. The valves are moved as close as possible to the combustion space boundary and form narrow spaces with respect thereto. The radii of the transitional arcs from the valve-end faces to the combustion space boundary increase continuously from the narrow spaces in both circumferential directions of the combustion space boundary and reach their maximum values in the center plane between the valves. The combustion space curvature is matched to the predetermined angles of inclination of the valves.

Abstract: An air flow in the combustion space which swirls or rotates about the cylinder longitudinal axis is produced for the fine distribution of the fuel by a correspondingly constructed inlet channel controlled by two inlet valves in a supercharged four-cycle internal combustion engine with direct fuel injection. With a low air mass flow, the rotary movement of the air in the combustion space is only weak and therefore prone to disturbance. An improvement is achieved by a change of the air flow in the inlet channel system. The valve actuation contains, for that purpose, an adjusting mechanism consisting of a piston-cylinder-unit fed with pressure oil, which effects in one operating function an automatic valve clearance compensation and which enables in a second operating function together with a controllable closure device in the pressure oil feed line a stoppage of one of the two inlet valves actuated in unison by the valve actuation.

Abstract: An intake device for an internal combustion engine is provided with an intake passage-length change mechanism for changing the effective length of the intake passage for each cylinder, and a valve timing change mechanism for changing the closure timing of the intake valve for each cylinder. The intake passage-length change mechanism is actuated, in a particular engine speed range, to change the effective length of the intake passage according to the engine speed so that the natural frequency of the intake system is tuned with the frequency of the pressure change in the intake passage which is determined by the engine speed, thereby enhancing the intake inertia effect to improve the engine output power. In the particular engine speed range, the valve timing change mechanism is actuated to make better use of the inertia effect enhanced by the intake passage-length change mechanism.

Abstract: An internal combustion piston engine having a plurality of intake valves and a plurality of exhaust valves per cylinder employs apparatus for disabling the operation of at least one exhaust valve upon decrease in speed of the engine below a predetermined level.

Abstract: An engine having an intake port which comprises a straight port and a helical-shaped port which are separated by a separating wall. A control valve is arranged in the inlet portion of the straight port and opens when the engine is operating under a heavy load. A projection is formed on the side wall of the separating wall, which defines the straight port and is located downstream of the control valve. A bypass passage connected to the helix terminating portion of the helical portion of the helical-shaped port is formed in the separating wall. The projection has an arc-shaped cross-sectional tip face which is directed towards the upstream of the intake port. The inlet opening of the bypass passage is formed on the tip face of the projection.

Abstract: Several embodiments of induction systems for internal combustion engines embodying pairs of intake passages each serving a single cylinder of the engine. In accordance with each embodiment of the invention, a device is provided for restricting the communication of the intake passages with the cylinder during idle operation so as to improve idle by precluding the backflow of exhaust gases into the intake passages. In some embodiments, the restricting means consists of throttle valves positioned in one or both of the intake passages and which are moved to a closed position when the engine is operating at idle. In accordance with embodiments of the invention, the cams associated with the intake valves provide for opening of one intake valve prior to opening of the other intake valve.

Abstract: An engine with three intake ports and three intake valves for each cylinder. The first intake port is a helical port. The remaining two intake ports have intake control valves, which open when the engine speed and the engine load are large and close when the engine speed and the engine are small. Air thus is introduced alternatively from the first port only or from all the ports. Fuel is injected in the third port between the corresponding intake valve and intake control valve.

Abstract: For a supercharged internal combustion engine having at least one engine cylinder, a fuel intake system comprises a primary intake passage for supplying a combustible air-fuel mixture to the engine cylinder, and an auxiliary intake passage including a supercharger for supplying at least supercharged air to the engine cylinder, said supercharger being constituted by a displacement air pump and adapted to be driven by the engine such as to produce and supply the supercharged air into the engine cylinder at least during the period in which the engine cylinder is held under the compression stroke.

Abstract: A fuel injection control system for an internal combustion engine having a fuel injection valve located near an intake port can control the timing of fuel injection in synchronism with engine revolution. The fuel injection control system improves fuel atomization characteristics and uniformity of air/fuel mixture entering the engine cylinders. The control system controls the fuel injection timing so that the fuel injection occurs within a valve-overlap period during which an intake valve and an exhaust valve are both open. In order to precisely control the fuel injection timing, the piston stroke of each engine cylinder is detected with reference to the crank shaft angular position.

Abstract: A reliability ensuring system for an internal combustion engine comprises an operating state detecting means for detecting the value of an engine parameter to be controlled which could affect the reliability of the engine and should be controlled when it goes outside a normal region. A preset value generating means generates a plurality of preset values with respect to the value of the engine parameter to be controlled, the preset values corresponding to different degrees of deviation of the engine parameter to be controlled from the normal region. An output signal generating means generates an output when the detected value of the engine parameter to be controlled exceeds one of the preset values for a predetermined time interval. The predetermined time interval is determined for each preset value so that it increases as the degree of deviation of the factor to be controlled from the normal region is reduced.

Abstract: An especially air-flow-cooled two-cylinder, four-stroke-cycle, double-piston engine (1) for the preferred use in motorcycles has for each cylinder (32) a camshaft (14) disposed horizontally on top in the cylinder heads (33) for the drive of valves (37 and 38) disposed in vertical V-positions. An intermediate shaft (4) is connected in the drive of the camshafts (14) which is driven by the crankshaft (3) with 1:2 down-gearing, with said intermediate shaft (4) being arranged parallel below the crank shaft (3), being driven at its front end--in driving direction--, carrying a pump wheel (12') of a lubricating-oil pump (12) and having two 1:1 drives (13) leading from its rear end in one tunnel each (36) of the cylinders (32) and cylinder heads (33) to the camshafts (14). The camshafts (14) are arranged in the V-space of the valves (37 and 38) and are in driving connection with the valves (37 and 38) by means of rocking levers (39).

Abstract: Stratification of charge in a four stroke internal combustion engine in which a stream of air issues from a duct (46) and is directed tangentially into a cylinder (2) to circulate about the cylinder adjacent to the cylinder walls. The air is admitted to the cylinder only while the exhaust valve (42) is open. The air circulates adjacent to the cylinder walls during the exhaust stroke and at least a portion thereof remains adjacent the cylinder walls during the subsequent induction and compression strokes. The combustible charge is admitted generally centrally of the cylinder and remains stratified with respect to the circulating air which contains the combustible mixture as a relatively concentrated central core whereby reliable ignition is achieved. The method may also be applied to two-stroke engines and to diesel engines.

Abstract: An engine intake system including a main intake passage leading to a combustion chamber through a main intake valve, a supercharging passage leading to the combustion chamber, and a supercharging pump provided in the supercharging passage. A rotary type timing valve is located in the supercharging passage and includes a rotor having inlet ports communicating with the supercharging passage at an upstream portion of the supercharging passage and an outlet port connected with the inlet port through a valve passage formed in the rotor. The rotor is driven in synchronism with engine rotation, the outlet port being arranged so that it is cyclically communicated with the supercharging passage at a downstream portion of the supercharging passage as the rotor rotates.

Abstract: Adjacent expansible chambers of an engine are provided with an intake runner set employing at least three runner passages conducting the working fluid from a common plenum to the expansible chambers, with at least one of the runners only serving one of the expansible chambers, at least another of the runners serving only the other expansible chamber, and at least still another of the runners commonly serving both of the expansible chambers. Preferably, a flow control is provided for one or more of the runners, preferably the common runner to manually or automatically control the flow of fluid through the common runner. Thereby, the runners for the expansible chambers may be adjusted in effective cross sectional area for tuned efficiency at different speeds. Preferably, such runners extend through the intake manifold and head ports without communication throughout their extent. The partitions forming the runners may be removable so that others of different shape or location may be substituted.

Abstract: A cylinder head 1 has four valves 2, 4 per cylinder and the desirable arrangement whereby the sparking plug 7 electrodes are in the center of the four valves. The sparking plug 7 is housed in a tube 29 to protect it from the oil in the valve gear region of the head. By appropriate choice of dimensions, it has been found possible to operate the valves 2, 4 via rockers 9, 11 by means of a camshaft 18 located in the vee-space between the valves, while still allowing room to accommodate the sparking plug 7. A desirable compactness is thereby achieved.

Abstract: An engine intake system includes a combustion chamber, a first intake port opening to the combustion chamber, and a second intake port opening to the combustion chamber. A shut-off valve is provided for blocking intake gas flow to the combustion chamber through the second intake port in a first engine operating region wherein engine load is relatively small, and allowing the intake gas to flow to the combustion chamber through the second intake port in a second engine operating region wherein the engine load is relatively large. A first valve actuating mechanism is provided for opening the first intake valve at a first timing, and a second valve actuating mechanism is provided for opening the second intake valve at a second timing.