[strat61caster]

Since this actually prompts discussion unlike the other post...

I believe when referring to an 'adiabatic' engine the idea is to allow the engine to run hot, as such less energy is allowed to be turned into waste heat and it creates better useful power. This is not a new concept, it's part of the reason Ferdinand Porsche designed the Beetle and his own sports cars to be rear engined, to reduce the cooling effects and squeeze more power (and thus more efficiency) out of his boxers. The limit to doing this is in the materials, obviously you can only get so hot until metal starts warping which was a problem with his VW's and 911's in the 60's since they were air cooled sitting in traffic on a hot summer day left several German cars stranded on the side of the road.

As for the power output per displacement, nothing tops BMW:
[ame="http://en.wikipedia.org/wiki/BMW_M12"]BMW M12 - Wikipedia, the free encyclopedia[/ame]

This is cool, but not extraordinary.

Edit: for those unwilling to skim the BMW article: 1.5L Turbo inline 4 with a peak output estimated at 1400 hp in 1986, lower output and better longevity with a reduction in boost.