The only thing more eye-popping than the aesthetics of Navistar’s CatalIST Super Truck project is its $7 million price tag – more than the GDP of some small island nations.
For comparison, $7 million would buy you three Ferrari LaFerrari FXX K sports cars, but the 1,035-hp supercar isn’t emissions-compliant, an area where International’s $40 million joint project with the U.S. Department of Energy shines.
DOE’s goal for its Super Truck program was to boost freight efficiency by 50 percent, a target CatalIST obliterated with a 104 percent improvement. Against a model-year 2009 baseline truck, CatalIST achieved fuel efficiency of 13 mpg and demonstrated 50.3 percent brake thermal efficiency (BTE) and a path toward 55 percent BTE.
“Freight efficiency is literally how much freight X miles per gallon at 65,000 pounds GVW,” says Dean Oppermann, Navistar’s chief engineer of advanced vehicle technologies – a man whom if CatalIST had a birth certificate would be listed as its father.
The first challenge designers had to overcome was to reduce the weight of the base vehicle to make it more efficient. Oppermann and his team shaved 2,000 pounds off the trailer, but added 1,500 pounds back through aerodynamic devices such as slotted skirts, a boat tail, gap treatment and 48-volt solar panels.
Aluminum landing gear and lightweight axles helped shave weight, as did the use of thinner DuraPlate walls on the Wabash trailer. Then there was the issue of the trailer floor.
“The decision was basically between wood and aluminum,” Oppermann says. “Wood is actually lighter, but we chose aluminum because wood is only lighter than aluminum on day one. On day two, it is no longer lighter than aluminum because it absorbs so much moisture from the outside, and you can’t control that.”
With a net loss of 500 pounds on the trailer, designers turned their scales on the tractor, where they managed to pull out 2,300 pounds.
The skirts and hood are carbon-fiber, and the wedge-shape cab is a carbon-fiber skin over the steel structure of an LT tractor. The windows and windshield are polycarbonate, which is lighter and stronger than glass.
Super-single tires and aluminum tanks round out the most of the 2,800 pounds Oppermann and his team were able to delete from CatalIST, an overall weight reduction that resulted in an 8 percent improvement in freight efficiency.
With 42 percent of the freight efficiency goal left to obtain, Oppermann and team set their sights on moving the air around the truck.
“One of the biggest uses of the energy that is coming out of the engine is to overcome drag of the vehicle,” he says, noting the CatalIST Super Truck was designed from the back forward. “The history of blunt body aerodynamics has demonstrated that at a point, the trailing edge starts to govern the aerodynamic drag more than the leading edge. Until you clean up the back, you can’t really unleash the opportunity of the front.”
In designing the trailer’s features, Oppermann maintained the common box shape to minimize the impact to potential shippers and carriers, but he added a boat tail that extends well below the underride guard and acts as an extension of the skirts at the rear of the truck.
A full-width reinforced carbon-fiber bogie treatment acts like a boat’s hull under the trailer, separating the airflow coming into the trailer axles.
CatalIST’s segmented Wabash trailer skirts flare inward as they reach the end of the trailer. Lower aerodynamics coming from the slotted skirt, Oppermann says, are offset by the fact they are lighter and come with other more practical advantages.
“If you had a full-piece skirt, it takes about four people to put it on,” he says. “A skirt like this, you can do with two people. These are collapsible. You can design a full-size skirt to be collapsible. However, if you hit something in the front and it collapses – because this skirt has such a long berth – you’re just going to end up deforming the skirt. By having smaller segments of skirts, they can collapse together, so it’s more robust. And if you damage it, you don’t have to replace the entire skirt.”
At full height, the skirts ride well above curb level. They’re not designed obnoxiously low to squeeze a fractional drop out of aerodynamic resistance; they’re one of CatalIST’s more practical everyday features. Aerodynamic improvements reduced the trailer’s drag coefficient by more than 30 percent.
The gap between the truck and trailer has been closed with passive gap treatment with a ball-and-socket design that features full articulation with a narrow gap.
While every Class 8 OEM produced a Super Truck under the DOE program, CatalIST is the only one that completely shed its mirrors – a move that slashed aerodynamic drag and wind noise. Mirrors were replaced with exterior cameras and interior pillar-mounted monitors.
“What also happens when you have something out there, you get turbulence over a mirror, and that turbulence is noise, that noise gets propagated into the vehicle, and you hear it as a background noise,” Oppermann says. “When you remove that mirror, there is no noise.”
Driving a truck with no mirrors takes some adjustment. Oppermann says most of the drivers who have tested the truck say it takes them about 20 miles to fully adapt to using the monitors. I didn’t clock it, but I got the hang of it in under 20 miles, and after a few minutes, I liked it.
The wraparound windshield design provides excellent and clear visibility over traffic from the driver’s seat, and the truck’s polycarbonate windshield also allowed designers to be more aggressive with its design to keep airflow attached to the truck longer as it comes over the A-pillar.
During my drive around the Chicagoland area, it started to rain. After the droplets hit the windshield, they barely moved. The ones that did move were forced to the left or right by the air crossing the windshield rather than straight up over the cab as you would expect.
A side effect of keeping the air attached to the truck around the A-pillar is additional noise reduction.
With the truck at speed on the Illinois freeway, I rolled down the window, and there’s no noticeable change in tone. I didn’t have to raise my voice to account for wind noise, because there was none. The only audible change came when a vehicle passed me; I could hear their road noise, but not mine.
Reduced wind noise aside, not having a bulky stalk-mount on the side of the door vastly improves visibility.
Going without mirrors isn’t the only distinct feature outfitted on the Lisle, Ill.-based truck maker’s Super Truck design. An air-over-leaf suspension drops the front of the truck and rear of the trailer for an airfoil shape across the top of the combination when it hits 50 mph.
“On the expressway, you’re not expecting to see curbs or bumps,” Oppermann says, “so having it as low as possible is a good thing. On the expressway, when it’s most important, you have basically a leaf-spring feel – a little bit firmer – that our customers like.”
When the truck drops to 35 mph, the bags reinflate.
“We want that ride height to come up, because you’re going to hit curbs or potholes, and what happens is now you get a little softer feel,” Oppermann says, “which is exactly what you want, because when you hit curbs, you don’t want it to be jarring your vehicle. It’s a little bit the best of both worlds.”
The happens with no input from the driver, and you can’t necessarily feel it while it’s happening. But you notice it when it’s complete, as the driver’s seat feels ever so slightly tilted forward.
If driving a real-world Transformer down the Interstate wasn’t cutting-edge enough, the leaf spring that supports the air suspension is a production-viable composite similar to what you’d see on a Corvette.
The use of a 6X2 axle was low-hanging fruit in terms of boosting fuel efficiency, and Oppermann and his team addressed traction concerns with load biasing.
At lower speeds, the load is biased on the drive axle by taking the air out of the tag suspension. The opposite happens on the expressway; at 50 mph, when ride height changes, the weight is biased to the tag axle to take advantage of its lower rolling resistance.
All of this happens without the driver knowing, or feeling, that it’s taking place until you slide your fuel card into the pump after clocking just more than 13 mpgs.
CatalIST’s engine is a base A26 engine with upgrades to help achieve a 50 percent BTE, including a variable speed water pump, friction coatings, higher peak cylinder pressures and higher-flow cylinder heads. The engine is attached to a 10-speed direct-drive automated manual transmission.
A 1:91 rear axle ratio – the tallest rear axle ratio ever used in this type of application – keeps cruising rpms low, saving more fuel.
“What that means is this vehicle basically cruises at 65 mph at around 1,000 rpm,” Oppermann says.
The package of weight-savings and improved aerodynamics gives the truck an effortless and slippery feel on the road. The lack of wind resistance is obvious and that translates into a clear reduced need for power to move freight that is noticeable by simply peeking at the tachometer.
Advanced electrical system
CatalIST features 3 voltage buses. A 12-volt bus powers headlights and legacy components such as interior lights and the instrument panel.
A 24-volt supercapacitor supports the truck’s stop-start function. I’ve driven passenger cars with stop-start before, but this was a unique experience in a large truck. It’s an eerie feeling to be sitting at a stoplight and feel your truck shut off. But a simple goose of the accelerator fired the truck back up, and we were on our way.
The third bus is a 48-volt kinetic energy recovery system. A 15kW motor generator mounted to the engine captures energy when the service brakes or engine brake is applied, while a pneumatic kinetic energy recovery system tops off the air tanks.
“We do that to try and minimize the amount of time that the air compressor is on when the engine is being fueled,” Oppermann says.
Gone is a more typical mechanical HVAC compressor mounted to the engine and a no-idle sleeper unit. Equipped with the 48-volt system and with electric energy at its disposal, the entire HVAC system was converted to fully-electric.
“That’s important because when the engine shuts off, it won’t affect the interior of the vehicle,” Oppermann says. “It also makes use of the free electrical energy that we have.”
The truck prominently features a predictive cruise control that combines normal cruise control function and GPS. Navistar’s predictive cruise control technology was one of the technical innovations the company achieved through the program. Predictive cruise control looks ahead of the vehicle and recognizes the terrain and continuously calculates the most efficient speed and gear for optimal fuel economy in real time. Unlike conventional predictive cruise technology, the company’s predictive cruise control uses preinstalled GPS maps and the latest commercial route data to make adjustments to cruising speed without the need to pre-drive the route.
“Because we have GPS and maps on the vehicle, we know what the topography is of the road ahead,” Oppermann says, adding that the system is capable of making calculations up to 3 kilometers ahead of the truck in order to optimize speeds.
“This vehicle will actually fluctuate [speeds] because it’s picking what’s the most optimum speed to optimize the efficiency of the engine as a function of whatever the terrain is,” Oppermann says.
The predictive cruise concept encompasses much more than just the speed of the truck. It also sets the water pump speed, which helps keep the engine fan off.
“If we know that a hill is coming in the future, we can support that by preconditioning the engine,” Oppermann says. “We can speed up the water pump and bring that temperature down, knowing that it’s going to rise as we approach that hill, and minimize the amount on fan on-time.”
While a radiator fan may sound like an insignificant feature beyond keeping fluids at a cool operating temperature, that’s hardly the case.
CatalIST will cruise at 65 mph using only 80 hp. If you turn on a fan for a 13-liter engine, you can consume an extra 50 to 70 hp depending on engine speed. With cruise set at 60 mph, my speeds fluctuated as much as 8 mph – down to 52 mph – as the truck optimized shifting and acceleration, but unless we were grinding out a long or steep grade, the 60,000-plus-pound truck never used more than 100 hp on any instance during the entire drive. Often, the truck slipped itself out of gear and coasted for extended stretches of highway. The only fuel being used was the minimum amount to keep the engine running.
“You’d basically be doubling the amount of horsepower you need [to run the fan], so you want to minimize that activity,” Oppermann says, noting in fuel economy runs held in near-100-degree weather, the fan never came on.
The likelihood we ever see a production-model CatalIST is something south of zero percent, but production-viable components will be brought to market from the rolling proving ground.