AND,

The little droplets of oil, swarf (?? cool), and un-combusted (but soon to be combusted?) fuel are all competing for space in the total volume of the intake charge. Their presence in the charge volume does nothing more than reduce the amount of air (read OXYGEN!) entering the engine.

As our glow engines are already tuned rich-of-peak (modeler's lingo for rich-of-stoichemetric.), the presence of the effluent from the crankcase does nothing but drive the mixture further from stoichemetric. Does this enhance power output??? I sure don't know.

Plus, as EC points out, one must consider pumping losses.

Never had a YS engine, but do they not use some system(driven by crankcase pressure?) to pressurize the entire, including air (read OXYGEN), intake charge entering the engine. In that case, as is demonstrated by the power output of those engines, the loss of combustion efficiency and pumping losses are more than compensated for by the increased mass of fuel burned on each power-stroke.

If, indeed, the entire intake system of the YS is pressurized, then they are a horse-of-a-bit-different-color than is a Saito running at atmospheric pressure. hs's 1.25 runs at atmospheric pressure?

Things do get a little crazy around the solstice, don't they?