How Navistar’s SuperTruck Exceeded Goals
Photos: Jim Park
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Photos: Jim Park
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The unveiling of Navistar’s SuperTruck in late September completes the first round of the Department of Energy’s fuel efficiency improvement demonstration project. Like the three others before it, Navistar’s truck, dubbed CatalIST, exceeded the DOE’s goals and provides possibilities for actual operations. CatalIST achieved a freight efficiency improvement of 104% compared to the baseline vehicle (a 2009 ProStar-powered rig). Its engine achieved brake thermal efficiency of 50.5%, and 13 mpg in real-world over-the-road and urban duty-cycle test runs.
Aerodynamics played a huge role, while advanced technology such as kinetic energy recovery, off-engine accessory drives, variable-speed compressors, and lightweighting shared the rest of the glory. Navistar also brought some clever solutions to traditional problems that seem unique among the four SuperTruck projects.
“We engineered the aerodynamic design back to front,” says Dean Oppermann, chief engineer for advanced vehicles and the SuperTruck group at Navistar. “We are pretty well tapped today on what we can do with the tractor alone until we clean up the trailer. Once we did the trailer, speaking in relative numbers, a 2-3% improvement on the tractor became an 8-10% improvement because of the overall reduction in drag on the rear of the trailer.”
Engineers got closer to the highly desirable teardrop shape by lowering the ride height of the the trailer suspension and the Hendrickson air-over-spring steer axle suspension, giving the vehicle an airfoil-like top profile.
“At speeds above 50 mph, we drop the front and rear suspension by 1.5 to 2 inches,” says Oppermann. “The boat tail at the rear helps to reduce the low pressure area at the base of the trailer, too. That relatively small shape change is very good for air flow.”
The trailer features nose treatment and Wabash’s Ventix Drag Reduction system, essentially vented side skirts. There is also a fairing in front of …Read the rest of this story
