[Diesel_Dave]

90% mechanical & 44% brake thermal efficiency are already within the range of modern diesels (at least at peak efficiency operating points). Interesting concept non the less. The potential mechanical efficiency advantage I see would be lower side forces on the piston.

I think the motion of the piston is still the basic slider-crank motion, so as far as the in-cylinder combustion, I think everything should be identical. Therefore closed cycle efficiency (and I assume pumping efficiency) should be the same as a conventional engine. So, the only advantage this engine would have efficiency-wise would be the mechanical efficiency. Even if the friction goes to zero, you're not going to get a 30% brake thermal efficiency advantage.

Interesting, but I guess I don't see a 30% efficiency improvement. The long-term durability of that "wristpin" joint concerns me too.