Spark Plug Rating Calibration

It has been found that the cooling rate of spark plugs in comparison with the indicated mean effective pressure on the piston can vary greatly between one cylinder head and another. Also, on occasions, a wide variation in ratings was found between those taken at one time in comparison with those taken at another time on the same cylinder head. These differences were due to many conditions, some of them controllable and some uncontrollable. Accordingly, it is necessary to arrive at a means of correction for these variables so that comparable results can be obtained at all times. This is necessary in order to establish acceptable standards for use in development work and in the application of production quality control. After considerable work on the investigation of rating correction means, it has been decided that carefully made spark plugs offer the best method of detecting and compensating for engine and operating variables. The spark plug models which have been determined as satisfactory for this purpose are listed in AS889. As a result of the research program, the following procedure is recommended for the use of calibration spark plugs.

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Current & Historical versions of this standard
Standard	Date published	?Status
ARP890A	1998-08-01	Revised
ARP890	1966-01-01	Issued