Fuel efficiency is increasingly becoming a significant driver in truck OEMs’ vehicle development plans, and that certainly was the case when Western Star set out to develop the all-new 5700XE revealed late last year. As evidence, the truck's nomenclature is a nod to the aerodynamic design and advanced technologies that enable fuel savings.

“XE—which stands for extreme efficiency—summarizes exactly what this new truck is all about,” said Michael Jackson, General Manager, Western Star. The truck blends “Western Star ruggedness together with aerodynamic innovations, and the most fuel-efficient powertrain available.”

The Class 8 on-highway truck is suitable for owner-operators and small to medium fleets in truckload/LTL, bulk, refrigerated, long-haul, and manufacturing applications. The 5700XE features a 126-in BBC (bumper to back of cab) with a set-back axle, and is available in a range of sleeper configurations.

“The 5700XE builds on proven aerodynamic technologies from parent company Daimler Trucks North America [DTNA] and adds edgy styling to set it apart from other trucks,” said Ann Demitruk, Director of Marketing for Western Star.

New features include an aerodynamic hood, roof, chassis, and cab fairings that reduce drag and increase efficiency. A new sweptback four-piece bumper includes an under-bumper valance, and even the new halogen headlights are optimized for aero performance.

Engineers specifically developed a visor to work with the slope in the hood’s rear air ramp to direct airflow over the cab. Roof and cab fairings sweep back for a tighter trailer gap and help direct airflow over and around the trailer.

Optional chassis side fairings reduce drag by up to 6%, the company claims, while providing easy access to batteries and the DEF (diesel exhaust fluid) tank.

A Western Star Twin Force dual air intake, which feeds a large centrally mounted air filter, also helps to improve efficiency.

Integrated powertrain package

The 5700XE can be outfitted with the Detroit Diesel DD15, which features the proprietary asymmetric turbocharger and next-generation ACRS (Amplified Common Rail Fuel System). Other engine options include the 600-hp (448-kW) DD16 or the DD13 engine for regional and “weight-conscious” customers.

The truck comes standard with the Detroit DT12 fully automated manual transmission (AMT), which can be mated to any of the Detroit engines offered. Computer-controlled shift and clutch actuators automatically select the most suitable shift pattern and clutch engagement for fuel economy and driving conditions.

The 12-speed AMT is available in direct or over-drive top gear configurations. Other features include a Creep Mode, which simulates a torque converter to improve low speed maneuverability; Skip Shift, which automatically skips gears to achieve cruising speed sooner; and eCoast, which enables vehicles to coast when the requested speed can be achieved or maintained with the engine operating at idle speeds.

“The DT12 has been available for less than two years, and we’ve had an extremely positive reaction from customers,” said Brad Williamson, Manager, Engine and Component Marketing for Daimler Trucks North America.

Western Star is offering the new integrated Detroit Powertrain engineered for “ultimate” efficiency. “Fleets can now choose a complete Detroit Powertrain for ease of service and optimized performance and efficiency,” said Demitruk.

The integrated powertrain package includes downsped DD15 engine rated at 400 hp (298 kW) and 1750 lb·ft (2370 N·m), DT12 transmission with Intelligent Powertrain Management (IPM), and Detroit axles with specific configurations and gearing.

Detroit Diesel announced in December that the IPM system will be standard on all DT12 AMTs paired with any heavy-duty Detroit engine, beginning in March 2015. IPM integrates pre-loaded terrain maps and GPS into engine and transmission functions to evaluate the road profile up to 3 mi (4.8 km) in advance and determine the most fuel-efficient vehicle operation (including vehicle speed, transmission gear, and engine rpm).

The company explains that because IPM uses the momentum of the truck to most efficiently move down the road, a route with varied topography (but no extreme change in elevations) provides the optimal opportunity for improved fuel economy. IPM is automatically “on” once the driver engages cruise control.

IPM also integrates with the Detroit Assurance suite of safety systems, which includes active brake assist and adaptive cruise control. The company notes that although Assurance operates in tandem with IPM, safety functions always take priority over fuel economy.

“Intelligent Powertrain Management technology employs many of the same behaviors that an experienced driver uses behind the wheel, but in many situations take actions that even the most experienced driver would be unable to employ such as engaging eCoast before cresting a hill,” said Williamson. “Ultimately, actions like this will help all drivers achieve greater efficiency with less fatigue.”

The 5700XE also comes standard with the proprietary Detroit Virtual Technician remote diagnostic service, which is part of the Detroit Connect suite of integrated telematics solutions. Detroit Connect includes Visibility fleet software and the forthcoming On-Board Tablet, as options for the 5700XE.

“Our DTNA internal testing indicates that the 5700XE is competitive with the fuel-efficiency results of the leading truck model on the market,” said Demitruk.

Safety and productivity

Inside the 5700XE’s galvannealed steel cab is a fully adjustable steering column and a steering wheel with integrated controls for the stereo, cruise control, as well as a Bluetooth connection for mobile phones. A new turn signal stalk includes integrated wiper and high beam controls, and a new transmission control stalk on the right side of the column allows fingertip control of the engine brake and DT12 transmission.

Meritor WABCO is a major supplier of active safety features for the 5700XE, including the OnGuard ACC. Its OnLane lane-departure warning system gives audible, directional warning signals to let the driver know if the truck’s course needs to be corrected.

The radar-based OnGuard collision mitigation system provides visual and audible driver alerts through an in-cab dash display when the vehicle’s following distance could result in a rear-end collision. If the driver doesn’t take action, OnGuard’s active braking automatically de-throttles the engine and activates the service brakes.

ABS brakes with electronic stability and roll stability control help to stabilize the truck, reducing the likelihood of rollovers, skidding, and spinouts.

The 5700XE is hand-built at the DTNA Cleveland, NC, Truck Manufacturing Plant. Full production began in 2015.