ALTHOUGH the C.F.R. Engine-Test Method of knock evaluation, now designated as the Research Method, is accurate and reproducible to a remarkable degree, investigation developed that it was not adequately simulating service conditions as judged by the most critical technician or the less critical lay user.
To bring the laboratory method in line with road evaluation of a fuel, a definite technique of road test was evolved that, while not to be considered in commercially determining octane numbers, was regarded by the Committee as sufficiently accurate and reproducible to serve as the first step in the development of a satisfactory laboratory method.
With a satisfactory road-test method available, the next step was to test a representative group of fuels and then develop a laboratory method which closely approximates the road results. The method finally adopted-a logical outgrowth of the original procedure, evolved by modifications consistent with the development as originally contemplated-meets this requirement with an extremely close approximation of the road observations.