Competition for Bombardier's better idea will likely come from Honda and TCM who, with little fanfare and no advance warning, planted a new prototype 225-hp, four-cylinder FADEC-controlled engine in a corner of the Continental booth. Unlike the Bombardier designs, this engine is a horizontally-opposed design but also water-cooled. Departing from the Japanese preference for overhead-cam designs, the Honda/TCM engine has pushrods with four valves per cylinder. More in keeping with traditional aircraft engines, its displacement is 370 cubic inches. How are they getting 225 hp out of that? With a 9.5-to-1 compression ratio and a modified version of the Aerosance FADEC that uses automotive-style sequential fuel injection. Honda's Haruo Nakayama, the project's chief engineer, told us the engine can easily be scaled up to six cylinders and/or turbocharged for more output. Thanks to the FADEC, it will burn mogas or avgas. Nakayama told us the engine is designed with durability in mind, especially for the crankshaft and bearing train In the four-cylinder variant, it has five main bearings with one rod per journal. As with other Continental designs, the cam is positioned below the crankshaft.
According to Nakayama, the engine has been running in the test cell since February of 2002 and has flown a handful of hours in TCM's test-bed Cessna 337. Fuel specifics are in the .37 range, which translates to about 10.5 GPH at 75-percent power. It weighs only 200 pounds, which makes it both lighter and smaller than the Bombardier offerings and smaller than, say, a Lycoming IO-360 of similar horsepower. TCM offered no details on either cost or a certification schedule.