Common wisdom has it that little Cox engines need lots-o-nitro to run, because they're little.  Indeed, my Cox engines are failing to run right on low nitro fuel, although I haven't run out yet for some high nitro fuel to try them on.

Other, less common but still available wisdom has it that higher compression engines need less nitro, and lower compression engines need more.

So do Cox 049s need lots of nitro to run because they're little, or because they just don't have enough compression?

I just finished a head for a Cox 049, with (on purpose) _way_ too much compression.  With not one, but three head gaskets (all that I could round up, in fact) it ran out a tank of fuel quite happily, which the engine _doesn't_ want to do with its regular head.  http://www.metalworking.com/dropbox/cox_head-on_plane.jpg.

So -- forget common wisdom for the moment.  Has anyone in the group _actually run_ a Cox engine on low nitro fuel, successfully?  If so, what did you do to make it work?

   Mostly because they are little. There was a pretty good discussion on the topic in the 1/2A "Monoboom" article, but the surface to volume ratio makes smaller engines run cooler than ideal.

That's the explanation that I always hear, but it doesn't explain why I read about Europeans successfully using far less nitro in 1/2A engines, nor does it explain why using higher compression or fewer cooling fins wouldn't help immensely.

I couldn't find the article -- do you happen to have a link to it?

I'm trying to talk myself into making a diesel head for the thing, but that's like -- work.  Ick.

The TD has more compression, which may or may not make my point.

I was reviewing my "2-stroke model airplane engines" book last night, and right there in the section on overcooling he recommends more nitro, less cooling, or higher compression.  He was trying to make the point that you didn't have to shave the head, you could just add nitro -- I'm wondering about the opposite side of the coin, if I want an engine that'll run on the same thing my big planes do.