An internal combustion engine is described and includes a combustion chamber formed by cooperation of a cylinder bore formed in a cylinder block, a cylinder head and a piston. A plasma ignition controller is electrically connected to a groundless barrier discharge plasma igniter that includes a tip portion disposed to protrude into the combustion chamber. A current sensor is disposed to monitor secondary current flow between the plasma ignition controller and the groundless barrier discharge plasma igniter. The plasma ignition controller is disposed to execute a plasma discharge event. A controller is disposed to monitor a magnitude of the secondary current flow via the current sensor during the plasma discharge event. The controller includes an instruction set executable to evaluate integrity of the groundless barrier discharge plasma igniter based upon the magnitude of the secondary current flow during the plasma discharge event.

An internal combustion engine is described and includes a combustion chamber formed by cooperation of a cylinder bore formed in a cylinder block, a cylinder head and a piston. A plasma ignition controller is electrically connected to a groundless barrier discharge plasma igniter that includes a tip portion disposed to protrude into the combustion chamber. A current sensor is disposed to monitor secondary current flow between the plasma ignition controller and the groundless barrier discharge plasma igniter. The plasma ignition controller is disposed to execute a plasma discharge event. A controller is disposed to monitor a magnitude of the secondary current flow via the current sensor during the plasma discharge event. The controller includes an instruction set executable to evaluate integrity of the groundless barrier discharge plasma igniter based upon the magnitude of the secondary current flow during the plasma discharge event.

An extender for connecting a high-voltage source to a spark plug has a conductive member, a tube having an interior passageway in which the conductive member is positioned therein, and a boot affixed over an exterior of the tube. The boot is formed of a material having a rigidity less than a rigidity of a material of the tube. The boot has a first end adapted to connect with the high-voltage source and a second end adapted to be connected to the spark plug such that the conductive member is in electrical connection with the spark plug and the high-voltage source. The conductive member includes a spring that is adapted to electrically connect with the high-voltage source and the spark plug.

A spark plug for a gas-powered internal combustion engine, having a center conductor, an insulator surrounding the center conductor, a body surrounding the insulator, a center electrode connected in an electrically conductive manner to the center conductor, and at least one ground electrode that is connected in an electrically conductive manner to the body and forms a spark air gap with the center electrode. A shield that shields the spark air gap in the radial direction of the spark plug is located at the front end of the body. The shield includes multiple shield components that are attached to the front end of the body adjacent to one another in the circumferential direction of the spark plug.

A spark plug includes a terminal electrode extending in an axial direction of the spark plug. The terminal electrode has an end in the axial direction, and has a recess formed in the end of the terminal electrode. The recess has a bottom surface and an identifier on the bottom surface. The recess has a side surface parallel to the axial direction.

A spark plug includes a terminal electrode extending in an axial direction of the spark plug. The terminal electrode has an end in the axial direction, and has a recess formed in the end of the terminal electrode. The recess has a bottom surface and an identifier on the bottom surface. The recess has a side surface parallel to the axial direction.

A metal shell for a spark plug is made from a steel material that has increased carbon content and, in some embodiments, boron as well. The steel material is well-suited for extrusion because of its ductility, while maintaining requisite strength. The spark plug shell may have a reduced outer diameter (OD.sub.HL) at a crimped hot lock region, such as the case when the shell is used in smaller diameter spark plugs, such as M8 and M10 plugs. According to a non-limiting example, the spark plug shell steel material comprises 0.20-0.55 wt % carbon, inclusive.

A spark plug includes a center electrode, a tubular metallic shell which holds the center electrode therein in an insulated state, and a ground electrode which faces a forward end portion of the center electrode. The metallic shell has a penetration hole which penetrates the metallic shell in a direction intersecting an axial direction. The ground electrode has a press-fitted portion inserted into the penetration hole and fixed to the metallic shell, a projecting portion projecting toward an inner side of the metallic shell, and an insertion portion disposed between the press-fitted portion and the projecting portion, inserted into the penetration hole, and forming a space between the insertion portion and an inner surface of the penetration hole. An angle α formed between the inner surface of the penetration hole and an outer surface of the insertion portion falls within a range of 0°<α<90°.

A spark plug including a center electrode; a metallic member forming a tubular shape around an axis of the spark plug, holding the center electrode therein, and having a hole formed in a side wall thereof and extending in a radial direction; and a ground electrode supported in the hole and extending from the hole toward the axis. The ground electrode has a fixing portion formed of metal and fixed to the hole, and an ignition portion containing a noble metal, disposed on a side toward the axis in relation to the fixing portion, and having a discharge surface for forming a gap between the ignition portion and the center electrode. The absolute value of the difference in coefficient of thermal expansion between the metallic member and the fixing portion is smaller than the absolute value of the difference in coefficient of thermal expansion between the metallic member and the ignition portion.

A spark plug including a center electrode; a metallic member forming a tubular shape around an axis of the spark plug, holding the center electrode therein, and having a hole formed in a side wall thereof and extending in a radial direction; and a ground electrode supported in the hole and extending from the hole toward the axis. The ground electrode has a fixing portion formed of metal and fixed to the hole, and an ignition portion containing a noble metal, disposed on a side toward the axis in relation to the fixing portion, and having a discharge surface for forming a gap between the ignition portion and the center electrode. The absolute value of the difference in coefficient of thermal expansion between the metallic member and the fixing portion is smaller than the absolute value of the difference in coefficient of thermal expansion between the metallic member and the ignition portion.