Kenworth showcased its SuperTruck 2 demonstrator tractor and trailer at the ACT Expo in Las Vegas. The project was the result of a joint investment by corporate parent PACCAR and the U.S. DOE (Department of Energy). Contributing to the Kenworth effort were AVL (engine development), Eaton (powertrain development), the National Renewable Energy Laboratory, and The Ohio State University.

The demonstrator was developed over six years as part of the DOE SuperTruck program challenging truck makers to improve freight efficiency using a diesel engine as the main power source. However, Kenworth was planning for the future, the overall layout designed to be powertrain-agnostic and supporting zero- and near-zero emissions solutions. The truck can efficiently package fuel cells, hydrogen and natural gas tanks, and batteries without changing the basic cab.

“The goal was a 100% freight efficiency improvement over our 2009 Kenworth T660, which at the time was arguably the most fuel-efficient truck in the industry,” said Jim Walenczak, General Manager of Kenworth and PACCAR Vice President. “We surpassed the performance of that model to improve efficiency by up to 136%. This was realized through a combination of improving fuel efficiency up to 12.8 mpg while reducing our combination weight by more than 7000 lb.”

The result was the ability to haul more payload with an ultra-fuel-efficient tractor-trailer combination.

“SuperTruck 2 provided us with the opportunity to investigate new technologies at an early stage. We learned what worked and what didn’t,” added Walenczak. “As a result, we are able to commercialize new technologies much quicker than we would have otherwise.”

 

Bullet-train-like design

The unique look of the truck catches most of the attention. The team started with an ideal aerodynamic shape to begin the design process of the SuperTruck 2.

“At the start of the project, we asked ourselves, ‘What does the next generation vehicle for long haul transportation look like?’” said Joe Adams, Kenworth’s Chief Engineer. “What we produced pushes the limits in reducing aerodynamic drag while it also incorporates a new powertrain. But, with everything Kenworth, we wanted the SuperTruck 2 to embody ‘The Driver’s Truck.’ The result was a systematic approach to developing a futuristic looking, yet relevant vehicle with technologies that have the potential to be refined and commercialized.”

Key features of the design are a center-driver cab, a new sleeper compartment, and a trailer combination to resemble a bullet train.

“We wanted to push this beyond just a demonstrator truck,” said Jonathan Duncan, Kenworth’s Design Director and ArtCenter College of Design alum. “We wanted to show something dynamic and what the future of Kenworth might look like. Our headlamps take up the entire front fender of the truck. It’s striking; you can’t miss it as it’s going down the road.”

The aerodynamic design was partly enabled by the powertrain’s location between the frame rails, which allowed the key engine element to be lowered and placed behind the front axle. A “reverse-splayed” chassis allowed the engineering team to narrow the front of the truck and fully enclose the wheels under bodywork. The hood and chassis fairings are mounted directly to the cab, moving as one unit.

A variable-ride-height suspension system was developed to optimize aerodynamics when running on smooth interstates and it can be raised over rough roads for better clearance.

Combined, the aerodynamics measures resulted in a 48% reduction in drag as compared to Kenworth’s baseline vehicle.

 

Mild hybridization and lightweighting

Kenworth’s truck uses a PACCAR MX-11 engine rated at 440 hp (328 kW) mated to a PACCAR TX-12 automated transmission.

The truck features a 48-V electric generator for “mild” hybridization leveraging lithium-ion batteries recharged through regenerative braking. This allowed for the conversion to electrical operation for fans, steering, and coolant/HVAC pumps. The engine fan alone can draw up to 80 hp. The hybrid system provides an overnight engine-off “hoteling” solution. In addition, the 48-V generator powers the exhaust heater in the close-coupled aftertreatment system that demonstrates CARB 2027 ultra-low NOx compliance.

The SuperTruck 2 team managed a parallel project for energy efficiency testing by combining a PACCAR MX-11-based engine, the mild-hybrid 48-V auxiliaries, and energy waste recovery to bench test a program record 55.7% engine efficiency.

“We did this while keeping in mind the technologies we developed needed to be commercially viable,” said Maarten Meijer, PACCAR’s Senior Engineering Manager for Advanced Technology. “Today’s modern diesel engine demonstrates around 47% efficiency. Reaching 55.7% was a major step forward and could only be done by applying new technologies that had not been explored until today.

To put that efficiency number into perspective, if the engine were to go into production, it would lead to a 10% fuel efficiency improvement, he added.

Enabling more payload for the tractor-trailer combination was a critical element for the engineering team. The combination came in at 26,100 lb (11,840 kg), 7100 lb (3220 kg) less than a typical configuration, with the savings split 4100 lb (1860 kg) on the tractor and 3000 lb (1360 kg) on the trailer.

“These savings would give a fleet the option of running lighter with the same amount of goods they’d normally put in a trailer, or they could add 7100 more lb of payload,” said Adams. “There were a lot of things that contributed to weight savings.”

The 10 new concept tires used weigh 355 lb (161 kg) less than similar tires currently on the market, and they also have an extremely low rolling resistance—measuring 4.2 on the CRR (rolling resistance coefficient) scale versus 5.0 for typical high-efficiency tires.

“We also found that less fuel was required with the more fuel-efficient powertrain; this allowed us to put on a smaller 80-gal fuel tank to go the same distance as before,” added Adams. “So, here again, we’re saving weight. It all builds upon itself.”

 

Center-driver cab

Entering the cab is through a large driver-side door accessible by an extendable bottom step. Once behind the wheel, drivers have a panoramic view and user interface featuring a 15-in digital display with a configurable gauge layout, advanced driver notifications, and user-friendly menu navigation.

“We made the windshield very parabolic in plan view and smooth to the flow,” said Duncan. “We also went one step further and eliminated physical mirrors altogether, minimizing drag. The integrated digital mirror system enables enhanced rearview monitoring, with trailer tracking capability and night vision enhancements—a technology currently available in Kenworth T680 models.”

For off hours, Kenworth designed a unique sleeper berth.

“One of the features we’re trialing is a bed that folds down over the sofa,” said Duncan. “This provides a separate sleeping and sitting area. We also came up with a neat concept: having a tabletop that rotates down when you’re sitting on the sofa. You can actually eat or work then move the table to a different location without moving anything off the tabletop.”

 

Production ideas

While Kenworth’s SuperTruck 2 gives a potential glimpse of the future, its developers were looking at new ideas for production consideration.

“Working in the trucking industry is very exciting,” said Adams. “There are major challenges ahead as we continue to advance vehicle performance, all while keeping in mind the goal to be a carbon-neutral society by 2050. This will require tremendous technology changes in the trucking industry and partnering with the DOE on the SuperTruck 2 program was a tremendous opportunity to consider what will be possible as we look toward the future.”

The “world-class” research and development facilities and staff at the PACCAR Technical Center in Mount Vernon, WA, were key to the success of the SuperTruck 2 program.

“PACCAR’s continued commitment to technical excellence, quality, and innovation are evident in the investments made in powertrain development and validation facilities at the Technical Center,” said Phil Stephenson, General Manager of the PACCAR Technical Center. “Capabilities including a high-speed test track, climatic chassis dynamometer wind tunnel, engine test labs, and advanced simulation tools were key to developing and validating the advanced technologies delivered in SuperTruck 2.”

While the demonstrator uses a diesel engine as its main power source, Kenworth is showing a variety of powertrain options at the ACT Expo. The company’s lineup includes its lineup of zero-emissions solutions including the T680 hydrogen fuel-cell electric vehicle, T680E and K270E battery electric vehicles, and offered ride-and-drive opportunities for customers of the T680 FCEV and X15N natural-gas powered T680.