Hiya,
Another much more efficient IC engine (~
39.5%):
This engine design replaces the crankshaft with two counter-rotating cams that have three lobes each -- mainly what this gets you is mechanical torque applied to the output shat at 20 degrees past TDC, which is far earlier than the 60 degrees past TDC that is typical for a conventional IC engine.
These are well into the testing phase, and look to be quite viable.