Transonic

The principles of the gasoline engine have chugged along for a century now without much change. The last big evolutions were variable valve timing and the switch to fuel injection from carburetors. Now a flurry of innovations to boost fuel efficiency is in the pipeline. One of them comes from a startup, Transonic Combustion, which claims its technology delivers fuel into the cylinder in a supercritical state--essentially, a fourth state of matter (after solid, liquid, and gas) in which the liquid is heating above its boiling point at very high pressure. When gasoline is injected into the...