AIR - FUEL RATIO CONTROL A MINIMAL FIX FOR OCTANE RATINGS OVER 100

Fuels containing large amounts of aromatics can give fallacious Research (F-1) octane number ratings because their normal combustion rate in rich mixtures is so high that it affects the knockmeter like conventional “detonation.” This problem can be reduced if the rule is adopted never to rate fuels at mixture strengths richer than that at which the bracketing primary reference fuels give their maximum knock.

Since conventional automobiles seem to rate fuels at mixture strengths leaner than that at which primary reference fuels give their maximum knock, adoption of this rule would not exclude any effects of “road” interest.