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.

Abstract: In accordance with the present invention, a composition of matter is provided for forming a vitrified abrasive wheel having an inner core and outer rim of differing compositions wherein said outer rim contains cubic boron nitride. The composition for the preferred rim material is a mixture comprising between about 10 to 70% by weight cubic boron nitride, between about 5 to 60% alumina, and about 15 to 35% bonding medium; and the preferred core composition comprises between about 10 to 65% silicon carbide, 10 to 60% alumina, and 5 to 30% bonding medium. In another aspect, a bonding medium is provided which is compatible with cubic boron nitride and in one embodiment has an oxide composition comprising about 71% silicon dioxide, 14% by weight boron oxide, about 5% by weight aluminum oxide, and about 10% by weight sodium oxide.