Navistar announced that its SuperTruck II evaluation truck obtained 16 mpg during recent evaluation test runs, thanks to hybridization, aerodynamics, and other technologies.

Overall, the OEM said, SuperTruck II registered a 170% improvement in freight efficiency, among other advancements, over the 2009 baseline vehicle. It also achieved 55% engine brake thermal efficiency.

The International SuperTruck II project is a partnership between the truck maker and the U.S. Department of Energy. The ongoing SuperTruck vehicle evaluations are a joint project between several commercial vehicle manufacturers and DOE. The goal is to explore emerging technologies that can be used on future Class 8 trucks to reduce greenhouse gas emissions while increasing both fuel economy and freight efficiency. In SuperTruck 1, Navistar's SuperTruck beat DOE efficiency goals and attained 13 mpg.

The Interational SuperTruck II uses electric motors in conjunction with a conventional truck powertrain to provide additional torque when needed to reduce the amount of fuel the engine burns.

In addition to hybridization, the International SuperTruck II concept truck also proved innovative technical approaches to weight reduction, including rolling resistance technologies, aerodynamic improvements, and powertrain technologies, the OEM said.

Hybridization Path Toward Full Truck Electrification

“With co-funding by the DOE, Navistar engineers experimented with prospective technologies not currently available in the Class 8 truck market to accelerate the impact of sustainable mobility," said Russ Zukouski, chief engineer, global innovation, and principle investigator for International's Supertruck programs.

"The team concentrated its design on high-voltage electrification, utilizing hybrid technology on a path toward full electrification that has the potential to be commercialized in fully electric vehicles and improve customers' total cost of ownership and business operations."

According to the announcement, "Navistar is the only OEM to build a trailer to provide the most accurate testing results possible," said Dean Oppermann, chief engineer, advanced truck. "It includes a 100% composite box designed for minimum aerodynamic drag with light weight, integrated cross members, controlled underbody flow with composite aero treatments, next-generation solar panels with connectivity options, and ride height control."

'Full-System Approach'

International SuperTruck II was built as a hybrid vehicle featuring an internal combustion engine with high-voltage accessories and technologies, developed in partnership with Bosch.

Engine improvements were made in key areas including combustion, friction, gas exchange, and airflow through the engine.

A redesigned cylinder head with dual overhead cam engine and enhanced fuel system resulted in a 2% fuel economy improvement when compared to International SuperTruck I.

Aftertreatment system improvements included diesel exhausted fluid dosing, improved mixing and lower restrictions, new selective catalytic reduction (SCR) formulations for high-NOx reduction, and reduced cold-start activation time.

"A full system approach was required to achieve 55.2% brake thermal efficiency," said Jim Cigler, chief engineer, advanced engine. "Opportunities were identified by internal engineering teams along with research partner Argonne National Laboratory through detailed analysis and simulation.

"System suppliers such as Bosch, Jacobs Vehicle Systems, and Applied Nano Systems (ANS) brought new approaches to key systems that enabled laboratory success and yielded real-world fuel economy improvements. Navistar was able to identify new ways to push our engines to the next level of efficiency."

International SuperTruck II highlighted connectivity with next-generation predictive cruise control, as well as leveraging technologies and information within the larger Traton Group to explore vehicle-to-everything technologies to enhance safety and vehicle efficiencies, according to the OEM.

"Our goal is to continue to advance internal combustion engine technology as efficiently and sustainably as possible until there is parity with zero-emissions vehicles," said Opperman. "Development of both technologies concurrently ensures a smooth transition of technology to best serve customer needs. We are focused on the entire product ecosystem — product development itself, as well as infrastructure charging, service and support of vehicle operation, end of life for batteries."

Navistar's SuperTruck II project vehicle shares many of the same techologies and systems that Freightliner announced on its own SuperTruck II collaboration with DOE earlier this year.