Oggers, oggers, oggers...
You can rely on the first pages a quick google search brings you as much as you like, I'll rely on physics, thermodynamics and conservation of energy.
The problem is you just keep arguing about inefficiencies caused by operating the engine outside its most efficient range and somehow try to relate this to the thermodynamic efficiency of the cycle. In the same way that small throttle settings relate to inefficient operation, so does your high rpm "not much time for combustion, inefficient valve/igntion timing, or poor mixing/incomplete combustion" arguments.
They are consequences of the way the engine is operated, not the thermodynamic efficiencies of the cycle. To make it absolutely clear and to prevent you muddying the relationship between thermodynamics/compression ratio and operating an engine inefficiently, let's consider a very low RPM, full throttle engine.
Don't worry. there's so much wrong that I'm still considering where to begin!
This ACTUALLY means you just don't know. This is now the third time you've denied answering this. Instead, each time you seem to cherry pick my posts and then wander off talking about consequences of how the engine is operated. Don't worry, physicists have been trying to find away around the conservation of energy for hundreds of years - they too have been unable to.
Here it is, AGAIN.
It's about the total fluid heat change from start to finish (once the fluid is returned to atmospheric pressure). It is lower in a high compression engine.
I'm STILL listening.
Also why is it that both the piston engine and the turbine engine can have their efficiencies increased by increasing the pressure ratio (compression ratio for piston)? Is there some sort of simple thermodynamic explanation for this?
It's because the fluid absorbs less heat
Anyway, back to Google for you