Detailing Kenworth’s Sleek SuperTruck 2

August 1, 2024

Ryan Gehm

The Kenworth booth at the 2024 Advanced Clean Transportation (ACT) Expo in Las Vegas garnered much interest thanks to the reveal of its futuristic-looking SuperTruck 2. Developed over a six-year period as part of the DOE’s SuperTruck program, the demonstrator vehicle improved freight efficiency by up to 136% compared to the 2009 T660 model. The team improved fuel efficiency up to 12.8 mpg and reduced the combination weight by about 7,100 lb (3,220 kg) — 4,150 lb (1,880 kg) from the tractor and 2,950 lb (1,340 kg) from the trailer. The design led to a 48% reduction in drag compared to Kenworth’s baseline vehicle.

A Paccar MX-11 diesel engine, rated at 455 hp (339 kW), is paired with a Paccar TX-12 automated transmission and a 48-volt electric generator, creating a mild hybrid system to operate accessories and provide engine-off “hoteling.” The 48V generator also powers the exhaust heater in an in-house-developed close coupled aftertreatment system that demonstrated CARB 2027 ultra-low NOx compliancy. SAE Media interviewed Joe Adams, Kenworth’s chief engineer, at ACT Expo to discuss the SuperTruck 2 in more detail and to preview the upcoming SuperTruck 3.

Can you break down the weight savings?

Chassis, front end and cab were the three areas that we got the most weight out. A fully composite cab, so we’re not using a metal structure there. That’s a significant part of the weight reduction. And then redesigning that front end, we were able to take hundreds of pounds out of the design by narrowing the overall axle so that we get enough wheel cut [with the enclosed front tires]. We spent a lot of time with that. The way that we’ve designed our actual frame structure also is a little bit unique with the geometry that we have [reverse splayed frame rails], and that was a big part of the lightweighting. This new, creative front end [allows] the engine to sit lower and behind the front axle, and that also gives us a center drive position.

But obviously there were other areas. The 10 new concept tires we used weighed 355 pounds less than ‘like’ tires currently on the market, and those tires also had an extremely low rolling resistance – measuring 4.2 on the CRR 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-gallon fuel tank to go the same distance as before.

On the trailer, it really comes down to two main areas. The side panels are all designed specifically in a lightweight composite, and secondly, the kingpin area, which generally has a large amount of mass there. We were able to redesign that with lightweighting [in mind]. That’s sizeable — the whole combination tractor-trailer is about 26,100 pounds, which is impressive.

Are there any technologies developed for this truck that are in production now or will be soon?

There are two key things. One is the digital vision mirror system. We put that into production last year. The idea of that really started out of the research here. It’s not legal in the U.S. to take the mirrors off the truck; the OEM can’t sell it to you [that way]. There is a provision after I sell it to you that you then can take the mirrors off as an operator with an exemption. In Europe you can, so we introduced it there with our partners; DAF has the same system in Europe without mirrors. Having no mirrors is probably about a 4% aero improvement.

The second thing, it’s not in production today, but I can easily see the 48-volt system that we have here being a big part of the strategy needed for CARB and for 2027 EPA [NOx emissions] standards in order to preheat the aftertreatment so that it stays compliant either to 50-milligram or 35-milligram solutions, depending on the year. It used to be that we had some minor periods that we could exceed those limits in a transient situation. The regulations no longer allow those transient periods like at startup when you have the cold aftertreatment. So now we have to put a massive amount of energy into the aftertreatment at start so that we can stay compliant. So, the 48-volt power generation system as well as distribution on the vehicle is something that we will see in future products.

What role will diesel electric hybrid powertrains play in the future?

The EPA just came out with their Phase 3 greenhouse gas standards, which talk about a pretty sizable reduction that we have to introduce into the equation in 2027, 2028, 2029. As we look toward that, hybrid powertrains I think will be another option because there’s a fairly sizable savings in the fuel you’re burning by pulling the parasitic loads off.

We’re looking at heavy hybrid applications as well — something that you can drive 75 miles [with] zero emissions. Some regions in the world, that makes a lot of sense. For example, cities like Paris have said by 2035, zero emissions. So you can drive diesel on the road, then click a switch and run zero emissions in the city, drop your load, come back out of the city, then run diesel to get to the next city. If we see that kind of duty cycle needed [in the U.S.], the heavy hybrid is more suited for that.

Kenworth is doing the SuperTruck 3. Where does that stand now?

We just started last year. So it’ll be another four-and-a-half to five-year program. SuperTruck 3 is more focused on freight efficiency with battery-electric trucks. One of the things we’re doing is we’re bringing in actual freight operators into the equation. We’ve got one partner that we’re working with, and we’re going to let them run some [production] battery-electric trucks and give that as our baseline today. And then we’re going to apply technology on top of that over the next few years to drive up the freight efficiency. It’s going to be a fun project.

So not a lot of carryover from this SuperTruck 2 project?

The plan we’re on right now is to start with the baselining and really try to keep it more powertrain-focused. The reason why is we think that there’s more to be gained by looking at battery chemistry, charging cycle, discharging cycle, lots of other kind of calibrations in the powertrain. We think that that’s really the gold mine for driving up the freight efficiency with zero emissions – more so than saying, ‘Hey, I’m going to go reshape the cab’ or do something like that. So, our current plan is focusing on that powertrain side. We’ll have some information on that coming out probably in the fourth quarter.

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