If you don't want the other bits of your windmill to be affected by the wind, then just put airfrictionmult = 0 on everything except the windmill blades
"Spawn engines can't be stable if so light and powerful" You could create an engine with low weight and high power, and with the correct tuning it can be perfectly stable
Are you going to go with a collide engine like the one in the thread you posted? I want to use a spawn. trust me, I tried a collide one. 570 kg and 2.6 hp
I had some fun with this with the soundmod, but the sound files aren't included in uploading (and hardly anyone uses it either ) so I never bothered to upload it...
Linkage, I think I've seen that engine before. This one?
This concept is very rarely used in ic engines. It was more commonly used in steam engines to re-expand steam above liquification pressure which would then increase efficiency if we dig into Carnot's law