Clean Automotive Technology
EPA's engine research focuses on developing engines that are clean, efficient, cost-effective, and likely to produce real-world benefits.
Clean Diesel Combustion technology is one example of these innovative engine concepts. EPA's testing suggests the potential for a diesel engine design that uses innovative air, fuel, and combustion management, as well as conventional particulate matter aftertreatment, to achieve lower NOx levels without the need for NOx aftertreatment. EPA is developing this technology along with other diesel emissions control approaches (e.g., NOx adsorbers, urea selective catalytic reduction (SCR), etc.). Clean Diesel Combustion technology shows the potential to meet future diesel emissions standards without NOx aftertreatment.
Gasoline HCCI, or Homogenous Charge Compression Ignition, engine technology is currently being evaluated by the EPA as a cost-effective method to achieve diesel-like efficiency with gasoline emission levels. HCCI combustion is similar to diesel combustion in that it requires no spark plug. Sophisticated sensors create the perfect mixture of gasoline and air which is ignited by compression. HCCI has been shown to reduce greenhouse gas emissions, NOx and particulate matter with minimal aftertreatment, thus significantly reducing costs. EPA is demonstrating its gasoline HCCI engine technology in a shuttle bus equipped with series hydraulic hybrid technology.
How a Four-Stroke Gasoline HCCI Engine Works
The intake valve opens drawing a premixed homogenous air and gasoline mixture, or charge, into the cylinder chamber.
The piston compresses the homogeneous charge as it rises.
The compressesd homogenous charge ignites and drives the piston down.
When the piston rises again the exhaust valve opens allowing the exhaust to escape.
EPA is also evaluating the effectiveness of advanced alcohol engine technology, which has been optimized to burn alcohol fuels with diesel-like efficiency. Advanced alcohol engines can use either ethanol (E85) or methanol (M85) fuels. Alcohol engines emit significantly fewer greenhouse gases than conventional engines. Alcohol-based fuels can also help reduce our dependence on fossil fuels. EPA is demonstrating its advanced alcohol engine technology in an urban delivery vehicle equipped with series hydraulic hybrid technology.
EPA has partnered with several automotive and engine manufacturers to evaluate the production feasibility of these engine technologies. Using clean combustion engine technology in conjunction with series hydraulic hybrid drivetrains will improve vehicle fuel economy more than using either technology alone.
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Technical Papers and Presentations:
- Fact sheet: Clean Diesel Combustion: Clean, Efficient, and Cost Effective Technology (PDF) (2 pp, 382K, EPA420-F-04-023, March 2004, reviewed April 2012)
- Presentation and speaker's notes: A Path to More Sustainable Transportation (PDF) (13 pp, 368K)(presented August 29, 2004 at the 10th Annual Diesel Engine Emissions Reduction Conference (DEER) in Coronado, CA. Reviewed April 2012). This presentation includes an update on an EPA diesel combustion technology that meets the 2007 heavy duty standards with engine-out NOx emissions of less than 0.2 gm/BHP/hr without the need for any NOx aftertreatment.
- Presentation on SAE Paper 2004-01-0933: An HCCI Engine Power Plant for a Hybrid Vehicle (PDF) (24 pp, 727K) (delivered March 10, 2004, at the SAE World Congress in Detroit, Michigan, reviewed April 2012). This presentation describes work conducted at the National Vehicle and Fuel Emissions Laboratory to explore the potential use of a homogenous charge compression ignition (HCCI) as a power plant for a hybrid vehicle.