Delphi has a new gasoline engine that beats most hybrids
Imagine combining the best attributes of gasoline and diesel engines into one system and reaping fuel economy numbers that rival today's gasoline-electric hybrids like the Toyota Prius. Engineers have been dreaming this dream for years, but have been stymied by the problems such engines have to overcome.
Delphi, a major parts supplier to manufactures, thinks it's figured it out. Using a single-cylinder test engine, the company put the technology to the test under a variety of conditions and found it performed better than expected. They're now building a multi-cylinder version that will be very much like the production-level engine in a car would be and will test that to be sure the idea scales up.
The engine is a combination of diesel and gasoline engine combustion technologies, combining the best of both to achieve fuel economies that are estimated to beat today's midsized sedan's averages by more than 50%, according to the company.
The gains come mainly from the higher energy efficiency of a diesel engine, which is 40-45% efficient in energy extraction and use while a gasoline engine is usually less than 30% efficient. Diesel engines, however, require a lot of after-treatment to meet emissions requirements while gasoline engines do not.
The idea, which engineers have tried to accomplish for years, is to burn gasoline in the same was you do diesel, gaining the efficiency of diesel use without requiring the after-treatment to clean it up. The problem has been controlling knock and noise in such engines, since igniting gasoline with pressure rather than spark (like diesel) is often met with burns that go too fast, especially under shifting loads such as idling, accelerating and cruising.
Delphi's solution is to time three bursts of gasoline into the chamber, which avoids a too-rapid burn while burning the fuel faster and more thoroughly than happens in conventional gasoline engines, in turn getting more from the fuel. The tech uses off-the-shelf items currently available on the market, making adoption potentially faster should the engine prove itself in trials.
Delphi calls this gasoline-direct-injection compression ignition. It includes other strategies like re-directing exhaust flow into the chamber to help warm it up in between firing to bring the engine to operating temperature faster when starting cold. Advanced air intake control also helps optimize the fuel:air mixture in the chamber during combustion, optimizing burn rates.