Dave,

There is something that I cannot explain. The practical limit for glow engines is probably around 2 cu.in. Over that displacement the glow engines are not reliable. In contrast, when gasoline engines are over ~85 cc they start to shine vs. glow engine. I have been flying a DA - 100 in the last 3-4 years. This engine has more than 500 flights and still running great. There is something in the combustion process when glow engines are too big (or carburetion) that I cannot explain. That is probably why the glow engines over 2 cu.in. are not popular (besides the cost of fuel). Probably someone expert in combustion could explain.

Regards,

Vicente "Vince" Bortone