Here is the new thread I promised,

What about a different non-metallic substance for making piston rings?
Any other ideas about reducing friction or increasing efficiency in an engine?

 

Teflon coated piston walls I believe have been done (Honda maybe???) to reduce friction.
Using High strength aluminium alloys instead of steel for rotating parts would reduce rotating weight.
New bearing designs. The hydramatic bearings used currently are fantastic for holding huge loads while taking up little space, but they aren't the most efficient.

 

Sorry I can't elaborate in detail on these items but I have heard of a few things.

Replace bushings and traditional style engine bearings with roller bearings.

Full roller valvetrain.

Eliminate valvetrain all together by using electric solenoid operated valves.

Hollow cams and cranks.

Hypereutectic pistons and coated piston skirts

Variable valvetrain timing.

"looser" machining tolerances.