Abstract: A spark plug is installed in an internal combustion engine to monitor engine performance. The spark plug includes an outer shell having a central longitudinal axis and defining a first bore extending along the central longitudinal axis. The outer shell also includes a second bore that is offset from the central longitudinal axis. An insulative core is positioned in the first bore and defines a third bore concentric with the first bore. A first electrode is positioned in and has a firing end extending beyond the third bore. A second electrode including a firing surface is located adjacent to the firing end of the first electrode. A sensor is located within the third bore.

Abstract: A spark plug is installed in an internal combustion engine to monitor engine performance. The spark plug includes a core having a central longitudinal axis and defining a first bore extending along the central longitudinal axis. A layer of insulation surrounds the bore. A sensor is located within the bore. A first electrode is embedded in the core remote from the bore. The electrode includes a firing portion at a firing end of the spark plug. A ground electrode is arranged adjacent to the firing portion of the first electrode.