Readily available technology can cut the fuel consumption of passenger cars as much as 50 percent without impacting performance or comfort but would add as much as $9,000 to the price of new vehicles.
Such are the trade-offs in our quest to boost efficiency while maintaining our love affair with the automobile, and they are spelled out in a report by the National Academy of Sciences. The academy asked 12 engineers, scientists and industry insiders to examine commercially available technology and its impact on fuel consumption.
"Reducing the amount of fuel we use is an important goal for the nation and for the individual consumer," said Trevor O. Jones, chairman of the committee that wrote the report. "These technologies, whether adopted individually or in combination, offer the potential to meet that objective. Consumers will need to consider the trade-offs between higher vehicle prices and saving fuel and money at the gas pump."
The study is significant because federal fuel economy rules require new cars and trucks to achieve a fleetwide average of 34.1 mpg within six years. Federal regulators are currently working on even tighter rules that would take effect between 2017 and 2025.
There is nothing revolutionary about any of the technology the panel examined, and all of it -- gasoline engines with improvements like direct injection, so-called "clean diesel" engines and gas-electric drivetrains -- are being adopted by automakers to varying degrees. Ford, for example, has tweaked the 305-horsepower V-6 engine in the 2011 Mustang to return 31 mpg on the highway. Diesels, long popular in Europe, are making inroads in North America. And hybrids like the Toyota Prius and Honda Insight, are increasingly common, even if they remain a small fraction of vehicles sold each year.
But the report, "Assessment of Technologies for Improving Light Duty Vehicle Fuel Economy," provides a glimpse at just what those technologies add to the bottom line.
The committee responsible for the study estimated the fuel savings and added costs of boosting the efficiency of a conventional gasoline engine compared to using a diesel engine or a hybrid drivetrain. As you might expect, the cheapest improvements came by making conventional engines more efficient.
One of the cheapest things automakers can do is adopt cylinder deactivation. The technology allows six- or eight-cylinder engines to run on fewer cylinders when full power is not required. That can cut fuel use 10 percent while adding just $350 to $500 to the price of the car. Direct injection, cold-air induction, variable valve timing and other tricks can cut fuel consumption by 29 percent but add $2,200 to the cost of a vehicle.
Such technologies will only become more prevalent because internal combustion gasoline engines will remain the dominant drivetrain for 10 to 15 years or more, the report states. Despite the availability of diesels and hybrids, such vehicles accounted for about 5 percent of all vehicles sold in the United States in 2008, according to J.D. Power and Associates.
Speaking of diesels, the study says swapping a gasoline engine for a diesel would yield a 37 percent reduction in fuel use. So-called "advanced" compression-ignition diesels coming to market in the next five years will cut consumption another 7 to 13 percent. Such engines will, however, boost the sticker price by $4,600 for passenger cars and $5,900 for larger vehicles, the study states.
Hybrids have the biggest impact on fuel consumption -- and price. But the impact depends upon the application. A full hybrid vehicle, which uses electricity exclusively when traveling at low speeds and electricity to assist in acceleration -- offers the greatest gains. Such drivetrains can cut fuel consumption by up to 50 percent, but will add $9,000 to the price of the car, the study states. The Prius is an example of a full hybrid.
Mild hybrids, which use smaller electric motors and batteries and rely more heavily upon internal combustion, can use 43 percent less fuel while adding $6,000 to the cost of a vehicle, the study finds. The Honda Civic Hybrid is an example of a mild hybrid.
Regardless of the level of hybridization, the biggest gains come in vehicles specifically designed to maximize aerodynamic efficiency and minimize rolling resistance while using the smallest possible gasoline engine, the study states.
Automakers need not pack their vehicles with advanced technology to see improvements. Six-speed manual gearboxes (or seven- and even eight-speed automatics) can boost efficiency, as can cutting the weight of vehicles. Even simpler tricks like using low rolling resistance tires and making aerodynamic improvements can yield gains.
The Environmental Protection Agency is examining all the components in a typical automobile, what they cost to make and what it could cost to increase fuel economy. The results should provide a better idea of the impact increased efficiency will have on the price of new vehicles.
The panel was not asked to consider how long it would take to recoup in fuel savings the cost of the technology; that task will be left to regulators as they contemplate tougher fuel economy and emissions standards. Those regulators, the panel notes, should revise fuel economy testing procedures to reflect real-world driving practices and conditions instead of the ideal laboratory settings currently used.
Read the National Academy of Sciences report online here.
Photo: Esthr / Flickr
See Also:
- EPA, DOT Finalize Fuel Economy Rules To Save Oil, Cut Emissions, Create Jobs
- Mustang Makes 'Big Statement' With Power and MPG
- Study: 1 in 4 Consumers Considering a Plug-In Car
- Enviros, Automakers Praise New Fuel Economy Rule
- How Detroit Will Reach 35 mpg
- We Can Double Automotive Fuel Efficiency (Relatively) Easily
