In an engine (1), an ignition plug (22) is arranged between a first intake port (6) and a second intake port (7). In a case where a downstream end portion (71) of the second intake port (7) is divided into a first intake port (6) side and an opposite first intake port (6) side, an inner wall surface (71a) of an opposite first intake port (6) side portion extends in a direction toward the first intake port (6) as extending from an upstream side to a downstream side of the second intake port (7).

In an engine (1), when an intake valve (16) opens, a downstream end portion (61) of a first intake port (6) extends to direct to between a shade back (162a) positioned on a cylinder axis (C) side with respect to a valve stem (161) and a ceiling surface (51) facing the shade back (162a). As viewed in a section perpendicular to a direction perpendicular to an intake air flow direction, a second intake port side inner wall surface (61a) at the downstream end portion (61) of the first intake port (6) curves apart from a second intake port (7) in a direction from an exhaust side to an intake side as compared to the shape of an opposite second intake port side inner wall surface (61b) mirror-reversed to a second intake port (7) side.

In an engine (1), when an intake valve (16) opens, a downstream end portion (61) of a first intake port (6) extends to direct to between a shade back (162a) positioned on a cylinder axis (C) side with respect to a valve stem (161) and a ceiling surface (51) facing the shade back (162a). As viewed in a section perpendicular to a direction perpendicular to an intake air flow direction, a second intake port side inner wall surface (61a) at the downstream end portion (61) of the first intake port (6) curves apart from a second intake port (7) in a direction from an exhaust side to an intake side as compared to the shape of an opposite second intake port side inner wall surface (61b) mirror-reversed to a second intake port (7) side.

A compression ignited combustion engine has at least one cylinder and first and second gas intake ports in a cylinder head restricting a combustion chamber. One gas intake passage leads to the two ports and is widened in a Y-shaped end influencing gas entering each port into a tangential flow in opposite direction with respect to the flow into the other port. The first intake port is designed to allow gas entering this port to continue said tangential flow so as to enter the combustion chamber in a swirl in a first rotation direction, whereas the second intake port is designed to guide gas entering this port to also enter the combustion chamber in a swirl in said first rotation direction.

An applied-ignition internal combustion engine having at least one cylinder head comprising at least one cylinder and having a rotatably mounted crankshaft is provided. In the internal combustion engine each cylinder has an inlet opening, which is adjoined by an intake line, and an outlet opening, which is adjoined by an exhaust-gas line, each opening being equipped with a valve, each cylinder comprises a combustion chamber which is jointly formed by a piston crown of a cylinder-specific piston, by a cylinder liner and by the cylinder head. Additionally, the crankshaft is articulably connected to the piston of each cylinder, such that, as the crankshaft rotates about an axis of rotation, the piston oscillates along a cylinder longitudinal axis, where the cylinder longitudinal axis is perpendicular to the axis of rotation of the crankshaft.

An applied-ignition internal combustion engine having at least one cylinder head comprising at least one cylinder and having a rotatably mounted crankshaft is provided. In the internal combustion engine each cylinder has an inlet opening, which is adjoined by an intake line, and an outlet opening, which is adjoined by an exhaust-gas line, each opening being equipped with a valve, each cylinder comprises a combustion chamber which is jointly formed by a piston crown of a cylinder-specific piston, by a cylinder liner and by the cylinder head. Additionally, the crankshaft is articulably connected to the piston of each cylinder, such that, as the crankshaft rotates about an axis of rotation, the piston oscillates along a cylinder longitudinal axis, where the cylinder longitudinal axis is perpendicular to the axis of rotation of the crankshaft.

An ignition control system performs discharge generation control, in which a discharge spark is generated, once or a plurality of times during a single combustion cycle. The ignition control system successively calculates an approximate energy density based on a secondary current and a discharge path length. During a predetermined period after blocking of a primary current is performed during a single combustion cycle, the ignition control system calculates an integrated value by integrating the discharge path length at this time, based on the approximate energy density being greater than a predetermined value. The ignition control system performs the discharge generation control again based on the calculated integrated value being less than a first threshold.

An intake device for an internal combustion engine, the intake device includes: a housing constituting an intake passage; a valve element including a valve portion arranged to open and close a part of the intake passage, and thereby to strengthen an intake air flow; and a receiving portion which is formed on a bottom wall of an aeration passage of the housing, and which is recessed in an arc shape along a movement trajectory of the valve portion, the valve portion including an outer side surface which confronts a bottom surface of the receiving portion, which has an arc shape, and which includes a seal portion that has a raised shape, and that extends along an edge portion on an upstream side of an intake direction.

When it is determined that the combustion state during the catalyst warm-up control is unstable, an additional ignition is performed on the TDC side relative to the discharge period CP. In a first countermeasure example, an additional ignition period CP.sub.2 is provided on the TDC side relative to the ignition period CP.sub.1 at the normal time while performing normal ignition and injection. A second countermeasure example is carried out when it is determined that the combustion state is still unstable despite the first countermeasure example. In the second countermeasure example, an additional ignition period CP.sub.3 which is a longer period than the additional ignition period CP.sub.2 is provided instead of the additional ignition period CP.sub.2.

When it is determined that the combustion state during the catalyst warm-up control is unstable, an additional ignition is performed on the TDC side relative to the discharge period CP. In a first countermeasure example, an additional ignition period CP.sub.2 is provided on the TDC side relative to the ignition period CP.sub.1 at the normal time while performing normal ignition and injection. A second countermeasure example is carried out when it is determined that the combustion state is still unstable despite the first countermeasure example. In the second countermeasure example, an additional ignition period CP.sub.3 which is a longer period than the additional ignition period CP.sub.2 is provided instead of the additional ignition period CP.sub.2.