ORIGINAL: downunder
In this case you're completely wrong Dar. For assumptions sake, let's say the Enya can run for 10 minutes at full throttle on 150cc (about 5 ounces) of fuel at 10,000rpm. In that time the engine has turned 100,000 times or 50,000 power strokes. This means that each power stroke needs 0.003cc of fuel (which contains about 0.0006cc of oil).
The Enya in question is 8.7cc so it'll have a combustion chamber volume of approximately 1cc to give a C/R of 9.7:1. Now let's run that engine terribly rich by doubling the amount of fuel that goes in per power stroke to 0.006cc of fuel and let's assume that none of that fuel vapourises into a compressible gas. The combustion chamber volume shrinks to 0.994cc and the compression rises to 9.75:1, hardly enough for detonation even if it could ignite.
In the real world the fuel component vapourises and gets compressed so it's only the miniscule volume of oil remaining that can add anything to the compression.
Brian,
Please read about the exact situation I was talking about in [link=http://www.rcuniverse.com/forum/m_3504643/tm.htm]this thread[/link].
It does not talk about a steady state, very rich running situation, as does what you wrote above.
...And I fully agree that detonation cannot happen in this situation which you described.
That thread talks about a
specific situation, which occurs in certain larger glow engines, running at a
very rich, low RPM setting, during which a lot of excess fuel, in liquid state, has accumulated in the crankcase.
And attempting to increase RPM, by opening the throttle, causes all this fuel to be 'rushed' into the cylinder, within a few revolutions.
It does not do this only in theory, but in actual practice.
You are welcome to comment in that thread too, but with all the props thrown in this situation, you cannot say this cannot happen, as it actually does.