I’ve not heard that before… I thought the ~120F ROP point is where you get the best alignment between the cylinder pressure profile and the crankshaft angle, consistent with a lower CHT which enables the extra heat to be dissipated into the air, oil and exhaust.
There are lots of variables and I think there are multiple ways of looking at the same thing. Ignition timing introduces a new variable in relation to cylinder pressure profile, and the traditional measure of combustion chamber effectiveness is the amount of ignition advance required for peak power at full throttle, given a certain mixture. That aside, the basic definition of fuel efficiency and power means that what you’re trying to do for most efficiency is burn all the fuel, and what you’re you’re trying to do for peak power is burn all the air. That’s what varying the mixture from lean to rich achieves.
That aside, I have two nice planes and eight beautiful motorcycles and enjoy them all the same way. They are a fun and relatively inconsequential way to spend some of my take home pay. I don’t get more fun by getting into an anal retentive technology driven spin about them. They are just toys, and what I do to afford them all is keep them simple and work on them largely myself, under supervision of non-professional A&P friends who are mostly focused on making money elsewhere. Fuel consumption to within 10% doesn’t matter a bit – sometimes one of them will sit for a year while I play with the others. To each his own.
Thank god for the anal retentiveness that gave us the wheel and fire….
Shorrick you are 100% right about the engines of course but where are the alternatives?
There is one good thing about our 1950s aero-engines: it takes a lot to stop them in flight. That’s mainly a function of their primitiveness and complete lack of precision manufacturing. Like the 1966 USSR engine 
Talking about USSR: I am always fascinated by the escalators of the St Petersburg metro. They are very long as the metro is deep down (swamp lands). Those escalators are like 60 years old and they are made out of wood. Still going strong at the expense of having massive repair crews and clearances to big that a child can fall through the gaps. Like our Lycontosaurus
Yes, just as its a good idea to understand the difference between clearances and tolerances, its also a good idea to understand the difference between being effective and being precise. Obviously, Germanic manufacturers have always tried to achieve the former through the latter – with mixed success.
I think electronic ignition, with a timing advance a function of the rpm, would be nice, would not require any gas sensors, and would allow 91UL in perhaps all Lyco/Conti engines, but nobody would get more MPG in cruise…
Assuming a non-turbo engine, they might get better MPG in cruise if they go high enough that ignition can advance with reduced full throttle manifold pressure.
Some would react to that by saying its shocking that anybody would make a non-turbo engine 
A non-turbo aero-engine really does not make any sense at all. The fact that they exist is another lowlight of the state of aviation.
How about turbocharged human lungs, do they make sense? Should cabin pressurization be mandatory? The end game for wanting more and more, and being intolerant of the buyers economic considerations, is getting less and less people flying – which is of course the European way in aviation and always has been.
You might derive happiness and satisfaction from the fact that 1950s technology is still state of the art, I’m definitely not. Even in cars which never leave the ground and where weight is not nearly as important as with airplanes, non-turbo engines are being replaced by turbocharged engines.
I very much like cars from 1950s, working on them, driving them. However, I wouldn’t want them to my main ride. In aviation, I’m forced to which stinks.
One reason why turbos have not taken over the market is that they bring a whole load of trouble, on these engines which run at high power settings for a long time.
I could buy a TB21 but choose not to. Not one has yet made TBO, to my knowledge. I have been criticised for saying this by some TB21 owners but they have not found a single TIO-540 which made TBO, either.
The exhaust systems don’t last long either. I have just read an account from one owner saying basically that you are continually spending $1000s getting the exhaust repaired. Welding, welding and more welding, as he put it.
Non-turbo aircraft, with decent size engines, deliver a good combination of performance and altitude capability. My TB20 does about 140kt TAS at 11.5 GPH at low level, 140kt TAS at ~ 9GPH at FL160, and will climb to FL200 eventually (ISA). That’s pretty good…
Troubles with turbos is not an argument against turbos but merely shows the poor state of technology. The 1930s turbo and super charged Jumos made TBO, although that was not a particularly high number back then. The SR22T is supposed to be rather reliable. The TR182 also generally makes its TBO.
When I read that Mercedes invested €1 billion in the facelift of the E-class and another billion in a slightly improved generation of gasoline engines, it’s clear why aviation isn’t getting anywhere.
