When famed researcher-and inventor of the electric starter motor-Charles Kettering discovered that no compound worked as we’ll as tetraethyl lead to kick up the octane of gasoline, he couldnt have guessed that nearly 100 years later, science would still be looking for something almost as good. That the search hasnt born fruit is one reason-although not the only one-that we still fly behind magnetos, not the electronic ignitions that have been commonplace in cars for three decades. Its not for lack of trying. Teledyne Continental has had a certified

FADEC for piston engines for some eight years, homebuilders fly with various iterations of electronic ignitions and General Aviation Modifications intriguing PRISM system thus far exists only as a test article. And the tests confirm that these ignition systems can prevent detonation in high power engines burning lower octane unleaded aviation fuels. So whats the problem?

Dwindling Supply

Curiously, the aviation industry is at a similar crossroads as Kettering was in 1919 when General Motors set him off in search of an octane booster. As is the GA industry now, GM was worried that gasoline supplies would soon run out and the industry needed a way to both improve poor quality petroleum-based fuels and to use ethyl alcohol as a primary fuel. Alcohol has poor anti-knock qualities and of thousands of compounds tested to improve alcohols anti-knock qualities, nothing came close to tetraethyl lead. By the early 1920s, it was the standard for octane boosting.

But the Clean Air Act of 1970 forced automakers to rely on catalytic converters to meet emission standards and because lead fouled the converters, it was phased out of motor fuels. Except for airplanes, which at the far end of the performance/horsepower spectrum, still rely on Ketterings TEL for detonation margin. Nearly 90 years of advances in chemistry and physics havent changed that.

“As far as additives go, what youve got is what youve got,” says Earl Lawrence, who follows fuel issues for the Experimental Aircraft Association. On a trial basis in the U.S., the industry has produced unleaded aviation fuels in the 95- to 96-octane range and these are economic to blend and distribute. Thats good enough for low-horsepower, lower compression engines but higher power engines still need 100 octane, or near it. Lawrence told us exotic additives have been tried in the struggle for 100-octane numbers but, just as Kettering discovered, these compounds arent economically practical. Complicating the issue is the headlong rush to add ethanol to motor gas, which many pilots burn in airplanes approved for it. Ethanol damages rubber and fuel components in some aircraft.

Retard the Spark

With the thrust for additives somewhat stagnant, the industry has sought a