Hyundai and Delphi are building a Gasoline Direct-Injection Compression Ignition. This is basically a gas engine that needs no spark plugs.
The pistons of this engine have "soup bowls" cast into their crowns. The injectors can squirt fuel directly into the center of each bowl. The 14.8:1 compression ratio is a key enabler to the GDCI engine's operation.
Fuel efficiency rivals that of a diesel according to Hyundai's GDCI expert. That is due to lean fuel-air mixtures, minimal heat lost through the cylinder walls, no throttling, and the large expansion ratio. Apparently the engine adds up to 10-15% efficiency without switching to a troublesome fuel.
Experimental Hyundai gas engine runs sans spark plugs
Engineers have been studying this alternative for more than a decade. GM and Honda both demonstrated cars powered by homogeneous-charge compression-ignition engines running on gasoline. More recently, Hyundai and Delphi advanced the cause by switching to stratified charge (a rich mixture in part of the cylinder) in a 180-hp 1.8-liter four-cylinder using auto ignition from idle to a 4500-rpm redline. When the study moves out of the lab into two test cars later this year, it should be clear whether the combination of diesel efficiency and gasoline conven*i*ence is within reach.

The pistons of this engine have "soup bowls" cast into their crowns. The injectors can squirt fuel directly into the center of each bowl. The 14.8:1 compression ratio is a key enabler to the GDCI engine's operation.
Fuel efficiency rivals that of a diesel according to Hyundai's GDCI expert. That is due to lean fuel-air mixtures, minimal heat lost through the cylinder walls, no throttling, and the large expansion ratio. Apparently the engine adds up to 10-15% efficiency without switching to a troublesome fuel.
Experimental Hyundai gas engine runs sans spark plugs