THE first of the detonation surveys referred to is an extension of the survey of current methods of measuring the anti-detonation qualities of motor fuels; the second is a survey of the relative detonation characteristics of available motor fuels as determined by the routine method of fuel testing now employed at the Bureau of Standards.
The survey of methods presented includes a reference to the apparatus and methods described in the 1927 report, and the information regarding laboratories Nos. 1, 2, 6, 8 and 10 is not repeated; but since the other five laboratories, Nos. 3, 4, 5, 7 and 9, use modified apparatus or methods, the paper presents information regarding them as well as similar data for other laboratories.
Comparative data on the apparatus and methods described in the paper are presented in a tabulation which includes 20 laboratories. Of these laboratories, at least half rely on the listening method. Most of those who use the bouncing-pin method probably will agree that the novice finds the bouncing-pin indicator as temperamental as the ear is indefinite, according to the author. Nearly all the engines used are water-cooled, but at least one laboratory reports that more satisfactory results are obtained with air-cooled engines. Only six L-head engines are included in the group, yet three of these are used at laboratories where the compression pressure rather than the compression ratio is varied to obtain audible detonation. The English laboratories supply heat at a constant rate to the air entering the carbureter, while more than half of the remaining laboratories maintain the carbureter air at some definite temperature above room temperature.
The survey of fuels presented by the author includes a brief description of the method of test and comparative results on (a) 15 samples of gasoline typical of current refinery production, and (b) 6 composite samples representing the average non-premium gasoline available to motorists in different sections of the Country. The data are presented in tabular form and commented upon by the author.
In the Appendix, distillation data and knock ratings for 20 branded British motor fuels are summarized. Knock ratings on 20 branded American gasolines purchased from filling stations in the St. Louis district are also given. These gasolines were rated at the laboratory of the Roxana Petroleum Corporation, where a Ricardo E-35 engine is used for routine fuel testing.