On Sun, 21 Mar 2021 18:40:29 -0400, Dave Smith wrote:

Maybe he was speaking about 'engineering'. My hazy memory says that a
normally aspirated 4-stroke has a theoretical maximum efficiency around
25% at standard temp & pressure. (0 C & 1 atm).

However, supercharged 2-stroke diesel train locomotive engines are in
service which achieve around 67% with a 'boost' of 20 or so.

Engineer - trains, get it?

Seriously, what I do not understand is why they don't use mechanical
oxygen concentrators to bring it up a few notches. If you get rid of the
80% inert nitrogen and pipe a turbocharger into the supercharger, just
imagine what could happen.

Yeah, I know. Hot metal and pure oxygen is a recipe for disaster. We just
need to figure out how to make ceramic pistons, etc.