I'm not familiar with diesel engines but it's struck me as odd that giving their characteristics of quiet operation, large/ slower turning props, they are a natural for turn-around type aircraft.

Granted, the topic isn't strictly a classic pattern thing....but there must be a reason for why, over the years, tuned pipes and higher rev'n engines ...even a few gasoline engines....continue to get the nod.

Several years ago Cliff Atkins and Charlie Campbell experimented with a diesel in a pattern plane and had some success. Charlie told me that they worked as advertised, but were really a nasty mess.

Just last week Dave Platt was telling me about another negative of diesels that was forcing him to change an engine in one plane to glow. Apparently diesels are very sensitive to their running temperature in a way that has a nasty interaction with the throttle. The compression and mixture are set at full throttle with the engine warmed up. Throttling back causes the cylinder temperature to drop. Then when you throttle back up you don't get the top end power back, or I suppose it may even die.

Sorry all this info is second-hand.

------------------


I doubt that the engine dies on throttle-up, unless the final tune at working temperature is very lean. Which is possible, but I doubt it. We're just talking here.

I love model Diesel engines, but they just don't have the consistency of a made for glow, glow engine. Perhaps that is the problem. Perhaps an engine that is meant to be a Diesel from the beginning with fine throttling incorporated would do the job. But then you are still going to be stuck with that stinky, yucky Diesel exhaust problem.

The best thing that a Diesel conversion head can do is that it will let you swing a larger variety of propellers than a stock glow engine. Why? Because of the variable compression ratio's ability to alter the timing and to prevent the engine from running with the ignition timing too far advanced for the load being placed upon it. However, glow engines can be designed to accept larger prop loads, i.e., the OS .61RF engines of long ago, and they do a superior job than a converted glow to Diesel engine.