Take Kenworth’s new 52-inch mid-roof sleeper configuration for what it calls its “flagship” highway tractor, the T680.
Kevin Baney, Kenworth’s chief engineer, said that greater fuel efficiency for operators in regional haul applications is the main thrust of this mid-roof package.
“The 52-inch sleeper delivers a big package in a small footprint; it’s a very efficient design,” he explained. “The smaller package yields excellent weight savings of up to 700 pounds versus the T680’s 76-inch sleeper configuration.”
[Baney elaborates further on some of the T680’s mid-roof sleeper configuration’s benefits in the video below.]
“Many regional haul applications don’t utilize full-height trailers,” Baney added. “Operators who run tank, flatbed, heavy haul, lowboy and container trailers typically have lower trailer heights or lower payload heights than traditional 53-foot dry van trailers. The mid-roof sleeper is a more application-specific design and can be more efficient because it pushes less air.”
He also noted that the 52-inch sleeper is available with an aerodynamic roof fairing to improve fuel economy for customers who operate van body trailers or without a roof fairing for flatbed or tanker operators.”
Preston Feight, Kenworth’s assistant GM for sales and marketing, noted that the new 2013 version of the 12.9 liter Paccar MX-13 engine offered for the T680 (as well as for other truck models the OEM builds) also underwent a design improvement to help boost fuel efficiency – notably by shaving some 100 lbs. out of it.
“The immediate impact is an improvement in fuel economy of up to 3.5% with the 2013 MX-13,” he said. “That’s a significant gain for customers which may amount to about a $2,500 annual fuel savings for the typical long-haul truck averaging 120,000 miles per year.”
[While fuel efficiency isn’t typically a watchword in the vocational market, Kenworth’s new T880 – designed for the dump, mixer, refuse, and heavy haul segments – offers some interesting new features as you can see in the video below.]
Yet to show truckers how to truly maximize the fuel efficiency of their big rigs, Kenworth put together a special T680 model dubbed the “Advantage truck,” which integrates aerodynamics, powertrain and electronic efficiencies into a complete and cohesive tractor-trailer package.
“To gain the optimum in vehicle fuel economy, the trucking industry must view aerodynamics, powertrains, drivers and trailers in concert. They all must be integrated to maximize vehicle fuel efficiency,” Baney explained,. “That’s the premise behind developing the Kenworth T680 Advantage; showing the trucking industry what’s possible when you integrate the total vehicle.”
The T680 Advantage is equipped with the new 2013 model 12.9-liter PACCAR MX-13 engine, which as Feight mentioned earlier boasts a base fuel efficiency improvement of 3.5% over the previous iteration thanks being 100 lbs. lighter, along with a new common-rail fuel-injection system to optimize combustion, new engine software algorithms, and lighter motor oil viscosity requirements.
The MX-13 engine is then paired with an Eaton UltraShift PLUS automated manual transmission to optimize shift patterns for fuel economy. “This way it mirrors the abilities of great drivers shifting with a manual transmission,” said Baney. “Studies have shown that drivers may influence upwards of 30% of fuel economy numbers, so reducing the driver variable can significantly improve a fleet’s fuel mileage.”
The T680 Advantage also controls fuel usage with an electronic speed limiter and engine idle shutdown software. “As a rule of thumb, there’s an estimated 0.1 mpg gain for every mph reduced when the truck is running at freeway speeds. If drivers lower their top speed and keep it around 62 or below, they’ll definitely see fuel savings,” noted Baney.
“Our speed limiter helps put more money in the company’s pocket and can benefit drivers on incentive programs,” he explained. “The same goes for idling. Most engines burn up to an estimated 1 gallon per hour while idling. By using our engine idle shutdown timer, fuel-wasting idling is nearly eliminated.”
Baney said the idle shutdown goes hand-in-hand with the battery-powered idle management system on the truck. “It’s a new, factory-installed battery-based APU [auxiliary power unit] system for air conditioning that is tied directly into the T680’s ducting system,” he pointed out. “A fuel-fired heater provides full engine-off heating capability. Both are seamlessly integrated into the T680 to provide excellent, engine-off, heating and cooling.”
Another “given” that will improve fuel economy is utilizing cruise control. “Studies bear this out,” said Baney. “But, in the real world, there is traffic and the need to engage and disengage the cruise with changing road conditions. It can be a distraction for the driver to re-set the cruise, so in many cases, they don’t and fuel economy suffers.”
Thus Kenworth equipped the T680 Advantage with a Bendix Wingman Advanced System with adaptive cruise, we have radar sensors integrated with the engine and braking system to help maintain a safe distance from traffic while maintaining control of the vehicle’s throttle input. The truck also includes the Bendix SmarTire Tire Pressure Monitoring system, so tire pressure is kept at the proper pressure thus reducing rolling resistance for maximum fuel economy.
Finally, there’s the trailer. “Through countless hours of computational fluid dynamics testing we can work with our customers to help them in spec’ing proper trailer aerodynamics that complement the aerodynamics of the T680 – all the way down to the details such as trailer height, tandem location and even trailer rake,” said Baney.
Thus the Utility dry van trailer attached to our T680 Advantage comes equipped with a trailer nose fairing, side skirts, and a trailer tail. “Combined, they can provide a significant fuel economy improvement, which will vary depending on use, road conditions and other factors,” he noted.
A Laydon nose fairing also fills the gap between the tractor and front of the dry van to shield the trailer from the negative impacts of a crosswind. Its open design does not interfere with trailer connections.
“On its own, the fairing can improve fuel economy up to an estimated 3%,” said Baney. ”Completing the package is the ATDynamics TrailerTail, which has been tested to provide more than a 6% improvement in fuel economy when driven at typical freeway speeds.”
Yet Baney told me the key to making all of this work is for the OEM to really dive more deeply into a fleet’s spec’ing process, tapping both computer and real world sources of data to design a powertrain, tractor, and trailer as a single unit configured to maximize fuel savings for specific applications.
“We’re finding fleets are more willing to do this with us,” Baney told me. “That’s because fuel economy is just that much more critical now.”
