Cleaner Cars A to Z


September 2006
Read this issue of Greentips online


The United States is the world’s largest consumer of oil, with two-thirds of that oil going to fuel the transportation sector. As a result, cars and trucks are a major contributor to air pollution and health problems in this country, and are responsible for more than 20 percent of U.S. global warming pollution.
The recent oil pipeline shutdown in Alaska and the high cost of gasoline underscore the importance of reducing our nation’s oil dependence. Technologies are evolving that help do this by improving fuel economy and enabling alternative fuel use, but it can be hard to decipher the “alphabet soup” of high-tech terminology. Below is a summary of some of the terms you should know:

Vehicle Types

  • HEVs (hybrid electric vehicles): Hybrids combine an internal combustion engine with a battery and electric motor, offering the extended range and rapid refueling of a conventional vehicle but with the potential for much higher fuel economy. However, not all hybrids are created equal; some use the technology to increase acceleration rather than boost gas mileage. The UCS Hybrid Center website (see the related links) provides information about and comparisons of current hybrid models.
  • FFVs (flex-fuel vehicles): FFVs have a single fuel tank, fuel system, and engine, but are designed to run on any blend of gasoline and ethanol, up to 85 percent ethanol (a mixture known as E85 that can modestly reduce a vehicle’s global warming emissions such as carbon dioxide). Unfortunately, E85 fueling stations are not available in all states; check the Department of Energy’s Alternative Fuel Station Locator for a list of stations nearest you.
  • NGVs (natural gas vehicles): Honda is currently the only automaker offering passenger cars that run on compressed natural gas (CNG). CNG emits less air pollution and carbon dioxide than gasoline, but as with E85, CNG fueling stations are not widespread.

Technologies

  • VVT (variable valve timing) or VVLT (variable valve lift and timing) adjusts the operation of an engine’s valves depending on engine speed and power demand. By providing a better fuel/air mix and improved combustion, these technologies boost fuel efficiency.
  • AFM (Active Fuel Management), MDS (Multiple Displacement System), and VCM (Variable Cylinder Management) are brand names used by General Motors, DaimlerChrysler, and Honda, respectively, to describe their cylinder deactivation systems, which shut down half of an engine’s cylinders when the extra power is not needed. This is particularly useful for vehicles with six- and eight-cylinder engines.
  • CVT (continuously variable transmission) is an automatic transmission with an essentially infinite number of speeds, which enables the engine to operate near its optimal speed under all conditions.

Related Links

FuelEconomy.gov

Union of Concerned Scientists—Hybrid Center

U.S. Environmental Protection Agency—Green Vehicle Guide

U.S. Department of Energy—Alternative Fuel Station Locator

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