Ground design

Navistar says the S13 Integrated will be its best and last internal combustion powertrain yet

It will be the last internal combustion engine that Navistar will design from the ground up. And, officials assured during a major reveal of the S13 integrated powertrain at Las Vegas Motor Speedway this week, it will also be its best.

Navistar on Tuesday unveiled the world’s first integrated powertrain designed with as part of new parent company Traton Group. Navistar President and CEO Mathias Carlbaum noted that it was the largest project undertaken by Navistar in more than 50 years, developed over five years in close partnership with Sweden’s Scania brand of Traton and optimized for use in North America.

Goran Nyberg, Navistar’s executive vice president – business operations, said the new powertrain, when combined with aerodynamic enhancements to the International LT, will provide a 15% improvement in fuel economy over to the LT and the first-generation A26 engine, which was launched just five years ago. .

(Photo: Navistar)

The powertrain also includes a new 14-speed T14 automated manual transmission and a redesigned two-stage, single-box exhaust aftertreatment system. They were developed using a modular design system perfected over the years by Scania.

It’s not electric, but Carlbaum said the new S13 Integrated marks a significant “step” in the truckmaker’s journey to zero emissions. By 2030 Navistar expects 50% of its new vehicle sales to be zero emissions, rising to 100% by 2040. That leaves many diesel-powered trucks to be built over the next 18 years.

“Here we are today, launching an internal combustion engine,” he said. “There is no conflict there. On the contrary, internal combustion engines will be needed for many years until the electric vehicle can be fully adopted and when we have a cross-country infrastructure. countries available.

Carlbaum said the fuel economy and aerodynamic improvements mark “the biggest step towards carbon-neutral transportation our company has ever made”, adding that “this powertrain is certainly the most efficient we have ever developed”.

Global cooperation

Volkswagen took an initial 17% stake in Navistar about six years ago before spinning off the truck business as Traton Group and buying the remaining 83%. But almost immediately after taking its initial stake, engineers from both companies worked side by side to develop the S13 Integrated engine. This involved adapting a modular design approach that would serve all global members of the Traton Group.

“Think of it like Lego,” Carlbaum explained of this modular design approach. “All interfaces are common. It allows more options with fewer parts. The S13 Integrated is the start of this community, this modular thinking that we will bring to Navistar in the years to come.

An example of how Navistar engineers have contributed to the design is the inclusion of front and rear PTO options, which is not common in Europe with its cabover trucks. “We will have front engine PTO availability when we have it in Professional models due to the importance of the North American market,” said David Hillman, integrated powertrain marketing manager.

International LT
International LT. (Photo: Navistar)

The S13 takes a new approach to emissions control. Although it still uses exhaust gas recirculation, a new clean combustion cycle has been designed to significantly reduce the levels of EGR required.

As a result, the S13 does not require an EGR cooler, which is a source of costly repairs (replacement costs are around US$4,000). The variable-geometry turbocharger (US$2,000 replacement cost) was also eliminated, replaced by a simpler fixed-geometry turbo. Active Diesel Particulate Filter (DPF) regenerations (and associated fuel metering) are no longer required and DPF service intervals have been extended. If the truck reaches 8.2 mpg, the cleaning interval will be stretched to 650,000 miles (over 1 million km) – or a full life cycle if a fleet replaces its trucks in five years or less.

Reduced EGR results in higher formation of NOx. This NOx is reduced by a new two-stage, one-box after-treatment device with diesel exhaust fluid metered into the back of the turbo, with the second dose occurring as the gas enters the after-treatment device himself.

“We don’t see a lot of soot in the aftertreatment device,” Hillman said of the new design.

The engine, thanks in large part to the removal of the EGR cooler, loses about 30-52 lbs compared to the current A26 with Eaton Endurant transmission and Cummins aftertreatment system.

Michael Grahe, executive vice president – operations, said the company’s approach to exhaust aftertreatment stems from the difficulties fleets have with the engines currently on the market.

“We had, with this powertrain, the advantage of coming in late,” he said in an interview with “All the others have already started their engines, so we were able to study what they did.”

North American engine manufacturers first used EGR to remove particulates, followed several years later by additional SCR to reduce NOx, in accordance with progressive regulatory requirements.

“So they developed a [EGR] engine and then put the SCR on it later,” Grahe explained. “We designed from the ground up knowing we were going to use SCR, so we could play around with the different levers you can pull, avoid the soot, avoid the EGR cooler and have that handled by the SCR system. This is the advantage of being late in this race.

Other notable changes in the S13 over the A26 are a higher compression ratio of 23:1, compared to the 20.5:1 compression ratio seen in the current engine. The high-pressure fuel pump operates at 28% reduced pressure thanks to the revised combustion strategy, so less energy is required by the fuel pump and can be redirected to the vehicle’s power supply. A cast aluminum cam cover and oil pan are standard to reduce corrosion.

A new transmission

T14 transmission
T14 gearbox (Photo: Navistar)

The new T14 automated manual transmission was also designed from scratch. It is an overdrive design that can run direct drive in 13e Gear, where it is most efficient and will operate most of the time when specified with the most efficient power ratings.

It offers an unlimited combined gross weight rating and includes planetary gears for a more compact design and faster reverse gears. The T14 also has shorter pitches than competing models, for faster acceleration.

An electronic clutch actuator also contributes to quick and smooth shifting. “It doesn’t consume air during high back-and-forth maneuvers,” Hillman said of one benefit.

Components are precision lubricated for reliability and protection against any moisture entering the system. A heat exchanger quickly warms the internal temperature in cold weather for smoother shifting on start-up and keeps transmission oil cooler in hot temperatures allowing unlimited GCVWRs.

A new LT International with S13 integrated powertrain was shown at Las Vegas Motor Speedway on August 16. (Photo: James Menzies)

LT updated

The S13 integrated powertrain will go first in the LT highway truck and the RH regional carrier. International medium-duty trucks will be powered by Cummins engines. The LT got a few aerodynamic upgrades to complement the fuel savings the powertrain itself offers.

The new aero package includes: DEF and fuel filler closures; ruffle closures and modified lower skirt; and a new roof extension. Updates improve airflow around and under the frame, and between the space between the tractor and trailer.

The front gets a new bumper and grille styling, and the sleeper cab now features a 9-inch mattress and a fold-down sleeper for more space and improved comfort. An electronic parking brake is now standard and will automatically engage if a driver forgets to set it.

Customers looking for a 15-liter option over the S13 Integrated with 12.7 liters of displacement will still be able to get it. But Grahe questions the need.

“Why do you need a 15 liter?” He asked. “Is it really something you need or is it because you are used to a 15 liter and emotionally attached. There is probably a residual value difference because the market is used to it. But the level of performance of a 13 liter is a clear advantage in terms of consumption and weight. We are already seeing many of the larger fleets in North America recognize this and move to 13 liters [powertrains].”

A European version of the S13 Integrated was launched in Scania trucks in Europe last year. Here in North America, it is expected to go into production next summer and is currently undergoing cold weather (-40F in Alaska), hot (+110F in Arizona) and high altitude (in Colorado) validation testing. By the time it goes into production next summer, it will have received more than 4 million miles of road tests and 300,000 hours of dyno validation, the company said.