An Approach To Obtaining Road Octane Ratings In A Single-Cylinder Engine 570019
An approach to obtaining laboratory single-cylinder engine fuel octane ratings that agree with car road octane ratings is described.
The technique is based on attaining, in the single-cylinder engine, a general duplication of the combustion environment which exists in the multicylinder automotive engine. Because it proved suited to this purpose, a special single-cylinder power section mounted on a CFR crankcase was used. The influence of speed on fuel borderline ratings was in substantial agreement with automotive engine results.
Results were obtained on a variety of commercial gasolines and special blends representing extreme variations in hydrocarbon composition. Comparative rating work covered a variety of 1947–1952 and 1955 cars; automotive engine compression ratios ranged from 6.5 to 9.0, and ratios of 10, 11, and 12 were obtained with special engines, heads, and pistons. For fuels of 68 to 105 octane number, single-cylinder engine ratings agreed with car ratings with a maximum spread of three Octane units. In contrast to this, the ASTM Research and Motor ratings deviated by as much as 10 octane units.