As Fuel Economy Standards Change, Fleet Owners and Truck OEMs Require New Approaches
While increasingly stringent fuel economy standards are always a focus for the light-vehicle segment, they are top of mind for the U.S. trucking industry as well. Last month, U.S. President Barack Obama called on the U.S. Environmental Protection Agency (EPA) and the Department of Transportation (DOT) to create and issue new fuel economy and greenhouse gas standards for medium-duty and heavy-duty vehicles by March 2016.
In a statement issued by the White House, President Obama said that while heavy-duty trucks only account for four percent of the vehicles on U.S. highways, they are responsible for about 25 percent of on-road fuel consumption. The president’s push for the second phase of regulations affecting commercial vehicles is designed to reduce the nation’s dependency on foreign oil while decreasing greenhouse gases. According to the U.S. Energy Information Administration (EIA), diesel fuel costs have been steadily rising for the past decade (Figure 1), while the American Transportation Research Institute (ATRI) reported that diesel fuel costs reached $0.641 per mile in 2012 and now account for more than driver wages and benefits (Figure 2).
With increasing diesel fuel costs and tighter fuel economy regulations to come, fleet owners attending the Technology & Maintenance Council’s Annual Meeting and the Mid-America Trucking Show this month are talking to original-equipment manufacturers (OEMs) about optimized systems technologies and innovative component designs that meet the new standards while keeping their costs in check. Advanced material developments, system structure technologies, innovative component design, and validation engineering are key to reaching emissions standards and fuel economy goals.
Lightweighting and Fuel-Efficient Technologies
The use of advanced materials in component development to reduce weight is one way OEMs have increased fuel economy. Steel was an industry staple for nearly 100 years. Today, automakers have invested in lightweight materials, including aluminum, carbon fiber, and structural composites to replace steel and increase fuel economy without sacrificing safety, durability, and styling cues.
Engine downspeeding is another approach OEMs are taking to increase fuel efficiency for commercial vehicles. The challenge is directing the amplified torque, at lower driveshaft speed, through the internal drivetrain components so that they can perform under the extra stress for their expected lifetime and beyond. Drivetrain manufacturers are coming up with re-engineered axle and driveshaft solutions that support increased torque while shaving pounds in the process. For example, Dana’s new Spicer® AdvanTEK® 40 tandem axle can enable an engine at highway cruising speed to run up to 200 rpm lower than existing powertrain systems while still reducing weight and increasing axle efficiency. Developed with faster axle ratios, the AdvanTEK 40 can handle higher input torques, lowering engine rpm at cruising speed while increasing axle efficiency by up to 1.2 percent for specific on-highway duty cycles.
According to a study by the North American Council for Freight Efficiency (NACFE), fleet owners can also reduce weight by adopting a 6x2 configuration, which features one drive axle and one non-drive axle on the truck’s tandem. While the 6x2 setup is still considered non-traditional in the U.S. market, fleets utilizing this configuration report a reduction in fuel consumption. The 6x2 configuration employs one larger drive axle resulting in reduced overall axle friction and churning loss, and it is significantly lighter than the traditional 6x4 system. On the other hand, 6x2 systems are not ideal for all applications, as overall vehicle tractive performance is reduced and resale values are diminished. To offset these shortcomings, 6x2 systems, such as the Spicer® EconoTrek™ tandem axle, typically feature automatic weight-transferring functions and wheel-differential locks to partially address low-speed traction concerns.
When every pound counts, system configurations designed with fewer components can reduce extra weight. For example, Dana utilized an innovative magnetic-pulse welding process in developing the Spicer® Diamond Series™ driveshaft, which eliminates the center bearing, U-joint, midship shaft, yoke, nut, and washer parts for reduced complexity. By combining a long and strong single-piece, large-diameter aluminum tube with steel end fittings, this driveshaft weighs 40 percent less than traditional two-piece, all-steel driveshafts; reduces noise, vibration, and harshness; and maintains the durability of an all-steel system.
As diesel fuel prices continue to rise and emissions regulations become more demanding, the U.S. trucking industry will assuredly have to make continued adjustments. Fleet owners and OEMs will make progress by taking advantage of the many approaches available to meet the new standards.
- How has lightweighting affected your fleet business?
- What are some unique ways you’ve reduced component weight for your fleet?
- Would you consider a 6x2 configuration for your fleet? Why or why not?
Director of Product Planning
Dana Commercial Vehicle Driveline Technologies