For years, spark plugs have been used to ignite the compressed fuel-air mix inside the cylinders of a gasoline engine to produce power.
Now a new prototype engine is promising a future in which a gasoline engine behaves like a diesel engine, self-igniting the fuel as it is injected into the cylinder instead of using a sparking plug.
Called Gasoline Direct-injection Compression Ignition (GDCI), the process results in engines that are low in particulate emissions and high in efficiency.
Similar to the way in which diesel engines work, GDCI engines compress air within the cylinder before injecting partially-premixed fuel into the cylinder.
As the air compresses, it heats up. This heat is then enough to ignite the gasoline as it is injected into the cylinder without the need for a spark plug, producing an explosion which then provides the engine with its power stroke.
The result is an engine that benefits from Diesel-like gas mileage, while retaining low NOx and particulate emissions.
It's worth noting at this point that the concept differs slightly from Homogeneous Charge Compression Ignition (HCCI), in which air is mixed with fuel before compression occurs. In an HCCI engine, compression of the fuel/air mixture results in self-ignition, rather than introducing fuel to the hot, compressed air at Top Dead Center.
Back in 2010, Delphi Corp., along with research partners Hyundai America Technical Center, Wisconsin Energy Research Consultants, and academics from the University of Wisconsin-Madison, were awarded a $7.48 million grant by the U.S. Department of Energy to study and build a working GDCI engine.
Now, two years later, the team has presented its initial findings to the SAE 2012 High Efficiency IC Engines Symposium and the SAE 2012 World Congress in Detroit this week.
Using a single-cylinder research engine fitted with four valves with double-overhead camshafts and central injection, the research team admits that the technology is some way from being used in a production vehicle.
However, with computer models of a 1.8-liter GDCI engine promising a fuel economy 60 percent better in city driving than current 1.8-liter spark-ignition engines, the technology could offer automakers yet another way to meet tough Corporate Average Fuel Economy targets for 2020 and beyond.