Abstract: A direct injection diesel engine includes a cylinder head which is formed, for each cylinder, with a plurality of intake ports. At least one of the intake ports has an approximately straight throat extending tangentially to the cylinder and opening into a combustion chamber at upper reaches of swirling. Another of the intake ports has a throat opening into the combustion chamber at lower reaches of swirling. A glow plug extends downward from one side of the cylinder head, at which the intake ports open, toward a location between the other intake port. An exhaust port extends from another side of the cylinder head and opens into the combustion chamber.

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 combustion chamber structure including a cylinder head having a bottom surface for defining an upper portion of a combustion chamber, a piston having a top surface for defining a lower portion of the combustion chamber, an intake recess formed in the cylinder head for an intake port of the combustion chamber to define a part the chamber, an exhaust recess formed in the cylinder head for an exhaust port to define a part of the chamber. The intake recess is smaller than the exhaust recess in volume. An extended wall portion is formed at a boundary portion between the intake and exhaust recess in the cylinder head to extend along the intake port and project into the exhaust recess. An ignition plug is arranged in the vicinity of a tip end of the extended wall portion. A compact structure of the combustion chamber can be obtained with an improved combustion property.

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: 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 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.

Abstract: An intake system for a multicylinder internal combustion engine comprises an intake passage including a common passage portion opening to the atmosphere, first and second volume chambers communicated with each other by a communicating passage, and a plurality of discrete passage portions branching from the first volume chamber and respectively connected to the cylinders. The second volume chamber is arranged to communicate the discrete passage portions with each other at a portion downstream of the first volume chamber and the common passage portion is communicated to one of the first and second volume chambers. An on-off valve is disposed at each junction of the second volume chamber with the discrete passage portions to move between an open position and a closed position in which the effective cross-sectional area of the junction is narrowed to an extent sufficient to prevent reflection of the pressure wave generated in the discrete passage portion at the second volume chamber.