Road Tests Prove Fuel Economy Projections

Jan. 1, 2002
They may look like regular tractors, but they aren't delivering freight; they're road-testing design and fuel economy enhancements. It's all part of Kenworth's

They may look like regular tractors, but they aren't delivering freight; they're road-testing design and fuel economy enhancements. It's all part of Kenworth's research and development program, says Jim Bechtold, KW chief engineer.

“We don't work in a vacuum,” he says. “Our design and testing goes beyond computers and wind tunnels. We take what the engineers create and test it on the road to verify projections.”

Kenworth runs several test routes, ranging from 150 to 500 miles. Each route has unique elements. One simulates longhaul highway applications, while another has a 4,300-foot altitude change for mountain conditions.

Real World Tests

In 2001, Kenworth conducted roundtrip fuel-economy runs from its lab in Renton, Washington, to The Dalles, Oregon, a small town in the Columbia River Gorge about 100 miles upstream from Portland.

“We typically ran two identical trucks — with the exception of the engine — to The Dalles and back,” says Moses Luyombya, Kenworth's fuel economy project engineer. “It's a good test route because we encounter a lot of extreme weather, especially traveling into the wind up the Columbia River Gorge to The Dalles.”

Many of these test involved T2000s with different engines. All had a gross weight of approximately 74,000 pounds and a gap of 42 inches between the tractor and trailer. Combined runs totaled more than 6,000 miles.

To make each test as accurate as possible, drivers and trailers were switched halfway through the trip. “This eliminates any variables in driver performance,” Luyombya says. “When the day is done, we measure fuel. Differences in fuel mileage between the two vehicles should show a direct correlation from the test component on aerodynamics.”

Consistent Fuel Supply

These runs and those at the Paccar Technical Center measure fuel consumption in a manner consistent with standards established by the Society of Automotive Engineers. Kenworth even uses its own fueling trailer at the lab to help ensure consistent fuel for the test. The trailer carries six, 500-gallon fuel tanks. This allows Kenworth to run up to five trucks — each with its own designated tank — on long-distance fuel economy tests.

“We documented up to 7.69 miles per gallon during testing of the T2000,” says Luyombya. “All the results came in over 7 mpg with the lowest at 7.24. Overall, T2000s averaged 7.43 miles per gallon during these 500-mile roundtrips to The Dalles.”

While highway fuel economy tests are intended to validate computer simulations and wind tunnel findings, Kenworth also tests new aerodynamic devices and vehicle configurations. “The way a tractor interacts with a trailer has a big impact on fuel savings,” says Luyombya. “We've refined roof cap heights and shapes — and recently explored new devices to reduce the air flow drag behind the trailer.”

Precise Proving Ground Tests

Kenworth also is involved in testing conducted at the Paccar Technical Center in Mount Vernon, Washington, which has a 1.6-mile oval high-speed track. “For every test series, we run three tests using precise SAE Type 2 and 3 methods,” says Bechtold. “Closed circuit track tests cover at least 150 miles.”

For accurate and consistent results, tests involve a modified tractor-trailer and a control combination. Fuel economy is compared for three separate runs. Numbers must be consistent for the test to be verified.

“We find that there's very little variation between our runs. That's a credit to our drivers and to how carefully we monitor weather conditions,” says Bechtold. “Over three separate runs, our trucks are usually within 0.5% miles per gallon of each other, which is far better than the 2% that is allowed by SAE.” Last summer, fuel-economy test runs at the Technical Center also used T2000s operating with different engines. They all had a gross weight of 74,000 pounds and a gap of 43 inches between the tractor and trailer. Combined runs covered over 2,000 miles.

Results Above 7.18 MPG

“We documented up to 7.68 miles per gallon for T2000s during the tests on the Tech Center track,” Bechtold says. “All results came in over 7 mpg with the lowest at 7.18. Overall, the average was 7.42 miles per gallon.”

“The advantage of closed circuit track testing is that it's so accurate we can detect small differences in fuel economy that can't be documented on road tests,” Bechtold says.

To help improve fuel efficiency, Kenworth recently launched a major fuel economy awareness program. The company also has produced a “White Paper on Fuel Economy,” which can be electronically downloaded at the “Dynamics of Fuel Efficiency” link at The white paper includes actual T2000 results from the Renton to The Dalles and PACCAR Technical Center test runs.

A free copy of the white paper may be requested at: Kenworth White Paper on Fuel Economy, c/o Brandhammer, 121 Lake Street South, Kirkland, WA 98033.

View more Refrigerated Transporter news relating to alternative fuels, idle reduction, fuel conservation, fuel economy and diesel fuel prices.

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