FUJI IN THE AIR

Model Airplane News, Jun 2005 by Hahn, Greg

ABOUT A YEAR AGO, DON ANDERSON, PRESIDENT OF GREAT PUNES, showed me the Fuji 4-stroke gas engine. He explained that the engine had to be mounted upright because there was oil in its crankcase.

As a factory demo pilot, all I could think about was which airplane this engine would fit to make the best impression. With the way the engine sounded and its low-end torque, I thought it would be awesome inside a big, WW I fighter. It has been quite a while since something new in the RC world got me this excited! The Balsa USA V4-scale Fokker D.VII has an 88-inch span, and the Fuji 34cc engine fits perfectly; it's nicely concealed beneath the dummy engine I built for the D.VII. The engine sounds exactly as it should for a WW I biplane, and it swings huge props!

This unique engine needs to be handled similarly to a full-size aircraft engine. There are three main differences between it and all others, and they're all positive: low heat, perfect sound and high torque. It does need to warm up a bit before flight to get the oil temperature up. A cold engine won't transition well, so you can't just start up and go fly. The warm-up period gives you time to check the controls and settle your mind before you taxi to the end of the runway. Also, with internal oil to help dissipate heat, the engine runs very cool compared with any other engine you've ever run. The low operating temperature allows the engine's inherent torque to be put to good use. Using a very large prop usually means that sooner or later, the engine will overheat, lose power and then quit. Unlike 2-stroke engines, the Fuji 4-stroke produces good power between 2,500 and 4,000rpm-perfect for swinging propellers up to two sizes larger than what would be used for the displacement. For example, a 34cc 2-stroke would comfortably swing an 18x10 prop, whereas a Fuji 4-stroke of the same displacement easily turns a 22x10 and still maintains a good operating temperature. The larger, slower-turning prop also cuts down on noise, so you can hear the sweet "putter-putter" of the engine.

This engine sounds so true to scale that it's difficult to believe. It's a combination of the internal valve train and the low rpm required to fly. Two-stroke gas engines never sound "right" because their rpm are too high. Full-scale aircraft engines rarely turn more than 3,000rpm at takeoff, and they cruise at 2,000 to 2,400rpm; our "normal" model engines cruise at around 7,000 to 9,000rpm.

It has been fun working with the new Fuji engines. Fuji is working on a modified version that will run inverted, and I'm eager to see what else Fuji will come up with for the model gas-engine market. -Greg Hahn