Duddy, B., Lee, J., Walluk, M., and Hallbach, D., "Conversion of a Spark-Ignited Aircraft Engine to JP-8 Heavy Fuel for Use in Unmanned Aerial Vehicles," SAE Int. J. Engines 4(1):82-93, 2011, doi:10.4271/2011-01-0145.
In order to satisfy a single-fuel mandate, the U.S. Department of Defense has a need for engines in the 20 to 50 hp range to power midsized Unmanned Aerial Vehicles (UAVs) and the ability to operate on JP-8 also known as “heavy” fuel. It is possible to convert two-stroke aircraft engines designed to operate on a gasoline-oil mixture to run on JP-8/oil using the Sonex Combustion System (SCS) developed by Sonex Research, Inc. Conversion of the engine involves replacing the cylinder heads with new components designed to accept a steel combustion ring insert. Also required are glow-plugs to preheat the cylinder head prior to engine start. The converted engine produces the same power output as the stock engine operating on gasoline. Conversion of both a 20 hp and 40 hp engine was successfully achieved using the SCS.