The standards are administered in DOT by the National Highway Traffic Safety Administration (NHTSA) on the basis of U.S. Department of Transportation (DOT) to set appropriate standards for light trucks. The act established the Corporate Average Fuel Economy (CAFE) program, which required automobile manufacturers to increase the average fuel economy of passenger cars sold in the United States in 1990 to a standard of 27.5 miles per gallon (mpg) and allowed the U.S. In the wake of the 1973 oil crisis, the issue of energy security arose, and Congress passed the Energy Policy and Conservation Act of 1975 as a means of reducing the country’s dependence on imported oil. However, by the late 1950s, fuel economy had become important, leading to the first large wave of foreign imports. Engines became more powerful, and vehicles became heavier, bigger, and faster. And indeed, in the 1920s through the 1950s peak efficiencies went from 10 percent to as much as 40 percent, with improvements in fuels, combustion system design, friction reduction, and more precise manufacturing processes. As early as 1918, General Motors Company automotive pioneer Charles Kettering was predicting the demise of the internal combustion engine within 5 years because of its wasteful use of fuel energy: “he good Lord has tolerated this foolishness of throwing away 90 percent of the energy in the fuel long enough” (Kettering, 1918).
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Also included is a brief discussion of customer expectations, since performance, utility, and comfort as well as fuel consumption are primary objectives in designing a vehicle.įuel efficiency is a historical goal of automotive engineering. Although modeling is discussed in detail in later chapters (Chapters 8 and 9), a simple model to describe tractive energy requirements and vehicle energy losses is given here as well to understand fuel consumption fundamentals. This fuel energy is used to overcome (1) rolling resistance primarily due to flexing of the tires, (2) aerodynamic drag as the vehicle motion is resisted by air, and (3) inertia and hill-climbing forces that resist vehicle acceleration, as well as engine and drive line losses. The amount of fuel consumed depends on the engine, the type of fuel used, and the efficiency with which the output of the engine is transmitted to the wheels. A brief overview is given here of spark-ignition (SI) and compression-ignition (CI) engines as well as hybrids that combine electric drive with an internal combustion engine these topics are discussed in detail in Chapters 4 through 6.
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The primary concern here is with power trains that convert hydrocarbon fuel into mechanical energy using an internal combustion engine and which propel a vehicle though a drive train that may be a combination of a mechanical transmission and electrical machines (hybrid propulsion). This chapter provides an overview of the various elements that determine fuel consumption in a light-duty vehicle (LDV).