Internal combustion engines have the potential to become substantially more efficient, with laboratory tests indicating that new technologies could increase passenger vehicle fuel economy by more than 50%. FCA and its partners recently took major steps toward fulfilling this potential through a project supported by EERE’s Vehicle Technologies Office. This team improved the fuel economy of a vehicle similar to Chrysler’s Town and Country minivan by more than 25%, while also meeting the Environmental Protection Agency’s most stringent emissions standards.
FCA, Argonne National Laboratory, Bosch, Delphi, and Ohio State University designed, built, and tested a dual-fuel advanced combustion 2.4-liter engine with a number of extremely efficient features.
The engine in the vehicle has a high compression ratio (the ratio of the largest capacity of the combustion chamber to its smallest capacity), which enables it to derive more energy from a specific amount of fuel in comparison to conventional engines. In addition to allowing the engine to turn more fuel into mechanical work, a high compression ratio also results in lower exhaust gas temperatures with less wasted heat.
The engine’s gasoline direct injection system provides it with precise control over when and where it injects fuel into the cylinders of the combustion chamber. This increased control results in better efficiency, lower emissions, and more power. With gasoline direct injection, the engine can adjust the fuel-air ratio depending on the needs of the vehicle, such as at cruising speeds or going up steep hills. Unlike most gasoline direct injection vehicles that have a less efficient “full power mode,” this vehicle only used more efficient stoichiometric fueling, when the engine injects an even mixture of fuel and air during the piston’s intake stroke.
The vehicle also uses two-stage turbochargers, which allow the engine to access extra power without needing to increase its size. Turbochargers push more air and fuel into the combustion chamber than it would have otherwise, increasing the efficiency of the combustion process. This vehicle actually has two turbochargers – one for low-speed boost and one for high speed – allowing for even more control over the power at any one time.
To reduce emissions, cooled exhaust gas recirculation technology in this vehicle moves cooled exhaust gas back into the engine cylinders, lowering the combustion temperature and decreasing pollutants produced by the engine.
In addition to these technologies, the vehicle also uses alternative fuels. To improve the timing of the combustion engine and reduce knock (explosive, uncontrolled combustion), it uses E85 fuel (up to 85% ethanol) when the vehicle is at higher loads, such as acceleration.
The vehicle also had some features that complement the engine’s technology to increase efficiency. An electrical mode management strategy enables the car to maintain the same state of battery charge as a conventional vehicle with less fuel. An innovative system to manage heat cooled the engine more efficiently than conventional ones, increasing fuel economy by about 1%.
With gasoline, the vehicle reached 38.5% peak brake thermal efficiency (a measurement of how well an engine converts energy from fuel into mechanical energy). The vehicle did even better when using gasoline and E85 together, reaching 41% peak brake thermal efficiency. In comparison, conventional combustion engines usually only reach 25% to 30% peak brake thermal efficiency.
The Vehicle Technologies Office (VTO) develops and deploys efficient and environmentally friendly highway transportation technologies that will enable America to use less petroleum. These technologies will provide Americans with greater freedom of mobility and energy security, while lowering costs and reducing impacts on the environment.
The Office of Energy Efficiency and Renewable Energy (EERE) success stories highlight the positive impact of its work with businesses, industry partners, universities, research labs, and other entities.