Abstract: An engine has a plurality of cylinders and the cylinders are divided into first and second cylinder groups so that the cylinders in each cylinder group do not fire one after another. An intake system for the engine has a plurality of discrete intake passages extending from the respective cylinders of the engine and merge into a junction chamber, a common intake passage which opens to the atmosphere at its upstream end and communicates with the junction chamber at its downstream end, a first communicating passage which is connected to the discrete intake passages for the first cylinder group at their intermediate portions and communicates them with each other, and a second communicating passage which is connected to the discrete intake passages for the second cylinder group at their intermeidate portions and communicates them with each other.

Abstract: Plural cylinders are grouped, for example, into two cylinder groups composed of plural cylinders having each inspiration stroke in an equal distance, and each of the grouped cylinder groups is communicated with a volume chamber. To this volume chamber is connected each of the independent air intake passages extending independently or separately from each of the corresponding cylinder. A first connecting portion is disposed to communicate the individual air intake passages for each of the cylinder groups with each other in a position spaced apart in an equal distance from an intake port. Further, a second connecting portion as a resonant passage is disposed to communicate one first connecting portion with the other connecting portion for each cylinder group.

Abstract: A mechanical supercharger is operatively connected to the engine output shaft when the engine speed is not lower than a predetermined engine speed and disconnected from the engine output shaft when the engine speed is lower than the predetermined engine speed. The engine load is detected and the predetermined engine speed is set lower as the engine load becomes lighter.

Abstract: In an internal combustion engine with a supercharger, a timing or timings for varying characteristics of kinetic supercharging effects of intake air are synchronized with a timing or timings for varying supercharging pressures by the supercharger. Reduction in engine torque at the time when the supercharging pressure is shifted, can be compensated for by enhancement in the engine torque generated at the time when the characteristics of the kinetic effect are varied.

Abstract: Plural cylinders are divided into cylinder groups consisting of the cylinders each having an equal inspiration stroke. The cylinder groups are so disposed as to allow their inspiration strokes to be apart from each other in a direction parallel to a crank axis in which a crankshaft extends. On its side surface, the cylinder head has an opening for an intake port which is communicated with an individual intake passage. Each of plural individual intake passage is extended from the respective cylinders for each cylinder group in the direction extending or elongated over the cylinder head and merged together at that location into a merged intake passage. The merged intake passage is extended toward the intermediate position between the two cylinder groups and thereafter curved, followed by extending toward the side of one side surface of the cylinder head.

Abstract: A multiple-cylinder engine has first and second groups of cylinders, the firing order being set so that the cylinders in each group do not fire one after another. An intake system for the engine has first and second groups of discrete intake passages which communicate with the respective cylinders in the first and second groups at their downstream ends and with first and second branch intake passage at their upstream ends. A circular passage communicates with the discrete intake passages at their intermediate portions so that all the discrete intake passages communicate with each other through the circular passage, and an on-off valve opens the circular passage when the engine speed is higher than a predetermined value and closes the same when the engine speed is not higher than the predetermined value.

Abstract: An intake system for a multiple-cylinder engine has a plurality of discrete intake passages which are substantially equal to each other in length and are connected to the respective cylinders at their downstream ends. The upstream ends of the discrete intake passages are merged into an integrated chamber, and an upstream side intake passage communicates the integrated chamber with the atmosphere. The integrated chamber has an upstream side end face and a downstream side end face, and the cross-sectional area of the integrated chamber increases from the upstream side end face to the downstream side end face, the upstream side intake passage having opening into the integrated portion in the upstream side end face, and the discrete intake passages respectively having openings into the integrated chamber in the downstream side end face. The area of the upstream side and downstream side end faces of the integrated chamber S.sub.0 S.sub.

Abstract: An intake system for a multi-cylinder internal combustion engine having an intake manifold that is made up of a common intake passage and separate intake passages that branch off from the common intake passage and connect to intake ports of the engine cylinders. An upstream throttle valve is located in the common intake passage. Downstream throttle velves located in the separate branched intake passages near the intake ports. A controller controls intake air actually introduced into the cylinder by actuating the downstream throttle valves to throttle down, smaller than the upstream throttle valve in a light engine load range and by actuating the upstream throttle valve to throttle down smaller than the downstream throttle valves in a heavier engine load range.

Abstract: A turbocharged engine is provided with a waste gate valve which limits the supercharging pressure in the intake passage downstream of the compressor of the turbocharger not to exceed a predetermined value. The intake passage has first and second pressure propagating paths downstream of the compressor. The pressure wave generated by the intake stroke of the combustion chamber is propagated substantially along the first pressure propagating path when the engine operates at a speed in a low engine speed range under heavy load and substantially along the second pressure propagating path when the engine operates at a speed in a high engine speed range.

Abstract: An engine is provided with a mechanical supercharger which is disposed in an intake passage of the engine and is driven by the output power of the engine. The supercharger is connected to and disconnected from the output power of the engine by a clutch. The engine has intake and exhaust valves which are opened and closed with an overlap time. A valve timing changing mechanism changes the overlap time in order to change the amount of air communicated between the intake and exhaust ports.

Abstract: A supercharged engine has a geometric compression ratio of more than 8.5, and engine specifications are set to establish a relation, Y.gtoreq.-1.75X+10, in which an intake port closing timing Y is expressed by a crank angle after the piston reaches BDC and an overlapping angle X is expressed by a crank angle for an overlapping time period during which the intake valve and exhaust valve are both open.

Abstract: An intake system with a simple and compact structure for an internal combustion engine having a plurality of cylinders each cylinder having an intake port, the opening timing of the intake ports being determined so that that of each cylinder overlaps with that of another in which the intake stroke takes place subsequently to that in the former, the intake system comprising intake passges each being connected to the intake port of one of the cylinders, a juction portion connected to the respective intake passages, a resonance intake passage connected to the junction portion at one end thereof, in which the intake pressure resonance effect is to be produced and control valves provided in the respective intake passages, the opening timing of the respective control valves being determined so as to be retarded relative to that of said respective intake ports under at least a low speed and heavy load engine operating condition.

Abstract: An intake system for a multiple-cylinder engine has first and second branch passages, a plurality of discrete intake passages for connecting the cylinders to one of the first and second branch passages, an intake air supply passage, an upstream side communicating passage for communicating the first and second branch passages with each other and with the downstream end of the intake air supply passage, and a downstream side communicating passage for communicating the downstream side ends of the first and second branch passages with each other. The firing order is set so that the cylinders connected to each of the branch passages do not fire one after another. The first and second branch passages and the upstream side and downstream side communicating passages forming a circular passage for supercharging the engine by resonance tuning effect of intake air.

Abstract: An exhaust gas recirculating system for a combustion engine has at least one cylinder communicating with a source of combustible air-fuel mixture through at least one intake port adapted to be selectively closed and opened for effecting the interruption and admission of the supply of the combustible mixture into the combustion chamber, the cylinder also communicating with an exhaust system through first and second exhaust ports both adapted to be selectively opened and closed.

Abstract: A intake system for a multiple-cylinder engine having a plurality of cylinders has a common intake passage open to the atmosphere at its upstream end, a plurality of discrete intake passages which communicate the respective cylinders with the common intake passage by way of intake ports, and a circular passage which is communicated with the cylinders and is adapted to propagate pressure waves generated by the intake strokes without reflecting the pressure waves. A part of the circular passage which does not form a part of the intake air path through which intake air is introduced into the cylinders is smaller in cross-section than a part of the circular passage which forms a part of the intake air path.

Abstract: An intake system for a multiple-cylinder engine has a main intake passage open to the atmosphere at its upstream end, a plurality of discrete intake passages which communicate the respective cylinders with the main intake passage by way of intake ports, and a circular passage which is communicated with the cylinders. The circular passage is adapted to propagate pressure waves generated by the intake strokes without reflecting the pressure waves, and is provided with a valve which opens the circular passage to permit propagation of the pressure waves in a predetermined high engine speed range. The length of the circular passage is selected so that the pressure waves resonate in the predetermined high engine speed range.

Abstract: An exhaust device for use in an internal combustion engine includes a plurality of independent passages each connected to an exhaust port of a respective cylinder of the engine. At least one communicating passage is provided to connect the independent passages to each other at points upstream of a junction where the independent passages are joined together. The communicating passage permits the exhaust gases from one cylinder to flow into the independent passages for the other cylinders, thus lowering the gas temperature and improving fuel comsumption.

Abstract: In a turbocharged engine, a bypass passage bypassing the impeller of the turbocharger is provided in the intake system to be opened and closed by a bypass valve. A flow control valve is provided in the intake system on the intake side or discharge side of the impeller. During heavy load operation of the engine, the bypass valve is closed and the flow control valve is opened so that all intake air flows through the impeller of the turbocharger. On the other hand, during light load operation of the engine, the bypass valve is opened and the flow control valve is partly closed so that the ratio of the pressure in the intake system downstream of the impeller to the pressure in the intake system upstream of the impeller is set near the surging line but below the same.

Abstract: An engine intake system including an intake passage opening to the combustion chamber through an intake port having an intake valve. A control valve is provided in the intake valve for cyclically opening the intake passage. Upstream the control valve, the intake passage is provided with a tank which functions to reverse the negative pressure propagated from the control valve into a positive pressure which is then transmitted to the combustion chamber to increase the intake charge. A timing control mechanism is provided for retarding the opening timing of the control valve in a low speed, high load engine operation.

Abstract: An intake system for an internal combustion engine has an intake passage comprising a common passage portion opening to the atmosphere, a surge tank connected to the downstream end of the common passage portion and a plurality of discrete passage portions branching from the surge tank and respectively connected to the cylinders. At least one interconnecting passage is provided to communicate each of the discrete passage portions with at least one of the other discrete passage portions at a portion downstream of the surge tank, and an on-off valve is disposed at each junction of the interconnecting passage with the discrete passage portions to open and close each junction. The on-off valve is opened at least when the engine speed exceeds a predetermined speed during heavy load operation of the engine.