This post is one in a series featuring the complete slate of advanced energy technologies outlined in the report This Is Advanced Energy.
As the dominant technology for passenger vehicles for over 100 years, gasoline-powered internal combustion engine (ICE) vehicles continue to improve their fuel efficiency and performance in dramatic ways. In addition to general improvements to reduce vehicle weight and improve drivetrain efficiency, several engine innovations are at various stages of development and commercial deployment. Three of these innovations are covered here: low-temperature combustion (LTC), lean burn gasoline combustion, and direct fuel injection.
LTC is a staged, ameless, lower-temperature combustion process that works by compressing a diluted fuel-air mixture until it auto-ignites. The mixture uses less fuel than normal because it is diluted with intake air or recycled exhaust gases. In addition, the lower temperature and staged combustion results in less wasted heat. Lean-burn gasoline combustion — in which fuel is burned with excess air — uses a similar diluted fuel mixture along with direct fuel injection, spraying fuel into the engine instead of through an intake port. Direct fuel injection reduces fuel use and improves efficiency and power.
There are currently no light-duty LTC engines on the market, but Nissan and Toyota have both developed heavy-duty diesel-fueled LTC engines. Lean-burn gasoline engines have also been slow to market, partly because lean-burn technology is not compatible with current catalytic converters, which require a near one-to-one air-fuel ratio. In 2006, Mercedes-Benz and BMW both introduced lean burn engines in Europe that achieved fuel economy improvements of up to 20%. Direct fuel injection is already common with diesel engines and is becoming more popular with gasoline engines.
Advanced gasoline ICE vehicles are considerably more efficient than conventional vehicles and have been shown to improve fuel economy by up to 75%. Direct fuel injection alone can improve fuel economy by up to 20% and in combination with lean burn technology can improve fuel economy by up to 35%. Advanced gasoline ICE vehicles provide one more option for consumers looking for higher fuel economy. Because they represent incremental improvements to a well-developed vehicle platform, they are a seamless and cost-effective option to increase energy security and save consumers money. Moreover, innovations made here can eventually find their way into other vehicles platforms, such as hybrid vehicles, resulting in even greater fuel economy overall.
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