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Vehicle Energy Management, Lightweight Materials Key to Increasing Fuel Economy

Toyota is looking at a number of available technologies, including, downsized powertrains, reduced rolling resistance, regenerative braking and weight reduction.

Special Coverage

SAE World Congress

DETROIT – Increasing powertrain efficiency, alone, will not be enough to meet the 35-mpg (6.7-L/100 km) U.S. fuel-economy standard set for 2020.

In order to meet the stringent federal regulations, auto makers and suppliers will need to focus on better management of energy use, a panel of experts says at the SAE World Congress here.

Of the total energy produced by a vehicle, only 22% actually is used, with the remainder diminished through chemical and thermal powertrain losses.

That energy could be saved through a variety of technologies available today, including electric-power steering, weight reduction and electric-motor management, says Paul Mascarenas, Ford Motor Co.’s vice president-product development-The Americas.

“Vehicle-control strategies have tremendous potential,” he says.

Jeff Makarewicz, vice president of the Materials Engineering Div.-Toyota Technical Center, says while the auto maker expects to meet fuel-economy standards ahead of schedule, he agrees it will take more than increasing powertrain efficiency to achieve the lofty goal.

“There are enabling technologies for more fuel-efficient vehicles,” he says. “And we realize we can’t take one approach to the solution.” Toyota is looking at a number of available technologies, including, downsized powertrains, reduced rolling resistance, regenerative braking and weight reduction.

“A 10% weight reduction results in a 6%-8% fuel-economy improvement,” Makarewicz says, noting the average vehicle weight has increased 882 lbs. (400 kg) over the last 20 years due to the addition of safety devices, more features and increased vehicle size.

One logical step to weight reduction is trimming the amount of steel, which accounts for 74% of an average vehicle’s mass. Toyota has been using more high-strength steel in its products, as well as magnesium and aluminum, although the latter two materials pose cost and forming issues.

“We believe more technical development is required (to reduce mass),” says Makarewicz, adding Toyota is exploring ways to use more titanium and composites in its vehicles.

Walter Grote, senior vice president-automotive systems integration at Robert Bosch GmbH, says advanced energy-management systems could go a long way in capturing previously lost energy and utilizing it in a productive way.

For example, such systems could monitor the high-energy loss from power steering and 10% depletion from engine idling. “A vehicle energy manager could manage supply and demand, and excess energy could be stored and used later,” he says.

While there are a number of solutions available, panel members agree taking weight out of a vehicle is the simplest and most cost-effective means to improving fuel economy.

Randall Scheps, marketing director-ground transportation for Alcoa Inc., a leading aluminum producer, says although aluminum costs more than steel, the price gap is narrowing, making the lightweight metal a more attractive option to decrease mass and reduce tailpipe emissions, and it’s fully recyclable.

Scheps says every pound of aluminum replacing steel results in a 22.9-lb. (10.4-kg) reduction in carbon-dioxide emissions over the life of a vehicle and improves fuel economy 6%-7%. Plus, the metal is highly complementary to advanced drivetrains.

He cites a recent survey, in which material and body engineers said 25% of future fuel-economy improvements would come from weight savings, while powertrain engineers pushed the figure to 50%.

Aluminum is making headway as a primary material for a number of automotive components, including hoods, control arms, bumpers and bodies-in-white, Scheps says. “It’s just the beginning.”

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