A fuel injector is configured so that, when seen from a top view of a combustion chamber, a first fuel spray flux and a second fuel spray flux sandwich an electrode part of a spark plug, and the electrode part is located outside of contour surfaces of the two fuel spray fluxes. A first injection angle between a center line of the first fuel spray flux and a vertical line and a second injection angle between a center line of the second fuel spray flux and the vertical line are larger than an angle between a center line of any other fuel spray flux and the vertical line. The second injection angle is made smaller than the first injection angle so that a distance from the electrode part to the contour surface of the second fuel spray flux is larger than a distance from the electrode part to the contour surface of the first fuel spray flux.

A fuel injector is configured so that, when seen from a top view of a combustion chamber, a first fuel spray flux and a second fuel spray flux sandwich an electrode part of a spark plug, and the electrode part is located outside of contour surfaces of the two fuel spray fluxes. A first injection angle between a center line of the first fuel spray flux and a vertical line and a second injection angle between a center line of the second fuel spray flux and the vertical line are larger than an angle between a center line of any other fuel spray flux and the vertical line. The second injection angle is made smaller than the first injection angle so that a distance from the electrode part to the contour surface of the second fuel spray flux is larger than a distance from the electrode part to the contour surface of the first fuel spray flux.

A spark plug, including a housing, an insulator situated in the housing, a center electrode situated in the insulator and a ground electrode situated on the housing, the ground electrode and the center electrode being situated relative to one another in such a way that the ground electrode and the center electrode form a spark gap, and the ground electrode including a core and a sheath surrounding the core, the core being made of a material which has a higher thermal conductivity than the material of the sheath, and a cross sectional area of the ground electrode being not greater than 2.76 mm.sup.2, the sheath having a wall thickness c of not greater than 0.4 mm in a first region of the ground electrode.

The spark plug includes an insulator, a metal shell, and a buffering member. The buffering member is filled in a space that is enclosed by an inner peripheral surface of the metal shell and an outer peripheral surface of the insulator. 3 mm.sup.2LT is satisfied in a case where: a length in a direction of an axial line of a filled portion filled with the buffering member is defined as a filling length L; a thickness, of a screw portion of the metal shell, that is half a difference left after subtraction of the inner diameter of the metal shell from the pitch diameter of the screw portion is defined as an effective thickness; and a minimum value of the effective thickness of a portion, of the screw portion, present rearward of an inner diameter reduction portion of the metal shell is defined as a minimum thickness T.

The spark plug includes an insulator, a metal shell, and a buffering member. The buffering member is filled in a space that is enclosed by an inner peripheral surface of the metal shell and an outer peripheral surface of the insulator. 3 mm.sup.2LT is satisfied in a case where: a length in a direction of an axial line of a filled portion filled with the buffering member is defined as a filling length L; a thickness, of a screw portion of the metal shell, that is half a difference left after subtraction of the inner diameter of the metal shell from the pitch diameter of the screw portion is defined as an effective thickness; and a minimum value of the effective thickness of a portion, of the screw portion, present rearward of an inner diameter reduction portion of the metal shell is defined as a minimum thickness T.

In a spark plug, a discharge gap is formed between a ground electrode and a central electrode. The ground electrode has a rod-shaped part and an opposing part. The opposing part faces the central electrode, and has a flat surface part and a slope surface part. The slope surface part is formed on a part of the opposing part in an extending direction of the ground electrode, and formed on the opposing part and gradually separated from the central electrode along a width direction of the opposing part. The spark plug has a ratio V/W within a range of 0.5<V/W<2.0. V indicates a length of the opposing part measured in a gap formation direction in which the central electrode, the discharge gap and the opposing part are arranged in order. W indicates a length of the opposing part in the ground electrode width direction.

In a spark plug, a discharge gap is formed between a ground electrode and a central electrode. The ground electrode has a rod-shaped part and an opposing part. The opposing part faces the central electrode, and has a flat surface part and a slope surface part. The slope surface part is formed on a part of the opposing part in an extending direction of the ground electrode, and formed on the opposing part and gradually separated from the central electrode along a width direction of the opposing part. The spark plug has a ratio V/W within a range of 0.5<V/W<2.0. V indicates a length of the opposing part measured in a gap formation direction in which the central electrode, the discharge gap and the opposing part are arranged in order. W indicates a length of the opposing part in the ground electrode width direction.

The spark plug includes an insulator, a metal shell, and a buffering member. The buffering member is filled in a space that is enclosed by an inner peripheral surface of the metal shell and an outer peripheral surface of the insulator. 3 mm.sup.2LT is satisfied in a case where: a length in a direction of an axial line of a filled portion filled with the buffering member is defined as a filling length L; a thickness, of a screw portion of the metal shell, that is half a difference left after subtraction of the inner diameter of the metal shell from the pitch diameter of the screw portion is defined as an effective thickness; and a minimum value of the effective thickness of a portion, of the screw portion, present rearward of an inner diameter reduction portion of the metal shell is defined as a minimum thickness T.

The spark plug includes an insulator, a metal shell, and a buffering member. The buffering member is filled in a space that is enclosed by an inner peripheral surface of the metal shell and an outer peripheral surface of the insulator. 3 mm.sup.2LT is satisfied in a case where: a length in a direction of an axial line of a filled portion filled with the buffering member is defined as a filling length L; a thickness, of a screw portion of the metal shell, that is half a difference left after subtraction of the inner diameter of the metal shell from the pitch diameter of the screw portion is defined as an effective thickness; and a minimum value of the effective thickness of a portion, of the screw portion, present rearward of an inner diameter reduction portion of the metal shell is defined as a minimum thickness T.

System and methods for operating a vehicle that includes a boosted engine are described. In one example, a spark plug may be adjusted between two operating states to reduce a possibility of pre-ignition and spark plug fouling. A first operating state may be conducive to operating the engine at light loads. The first operating state may be conducive to operating the engine at higher loads.