A Spark-Plug Adapted for Measuring Cylinder-Head Temperatures 370141

A NEW method for adapting a spark-plug to the measurement of cylinder-head temperatures is described, consisting in leading thermocouple wires through two holes down through the shell of the spark-plug and bringing them into contact with each other in the surface of the rim exposed to the combustion-chamber.
Engine tests were conducted to compare results obtained by this method of measurement with those obtained with a central-electrode couple, and also a couple incorporated in the spark-plug gasket, all three devices being incorporated in the same plug.
The thermocouple mounted as described in the paper was more responsive to engine detonation than the thermocouple mounted in the gasket but less so than the thermocouple mounted in the central electrode. It was less responsive to changes in wind speed than the gasket couple in the case of an air-cooled engine but more so than the central-electrode couple, and it is believed that a couple mounted as described gives a truer indication of cylinder-wall operating temperatures than can be obtained by either of the other methods.


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