Fleet Management News & Business Info | Commercial Carrier Journal
Issue link: http://read.uberflip.com/i/858523
commercial carrier journal | august 2017 29 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 soer feel, which is exactly what you want, because when you hit curbs, you don't want it to be jarring your vehicle," Oppermann says. "It's a little bit the best of both worlds." at 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. Using a 6x2 axle was low-hanging fruit in terms of boosting fuel efficien- cy, and Oppermann's 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. e 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 feeling that it's taking place. CatalIST's engine is a base Internation- al A26 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 ba- sically cruises at 65 mph at around 1,000 rpm," Oppermann says. e package of weight savings and improved aerodynamics gives the truck an effortless and slippery feel on the road. e lack of wind resistance translates into a reduced need for power that's noticeable by simply peeking at the tachometer. Advanced electrical system A 24-volt supercapacitor supports the truck's stop-start function. I've driven cars with this feature, but it's an eerie feeling to sit at a stoplight and feel your heavy-duty truck shut off. CatalIST also has 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. CatalIST has achieved fuel efficiency of 13 mpg. Gone is a more typical mechanical HVAC compressor mounted to the en- gine 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. "at's important because when the engine shuts off, it won't affect the interior of the vehicle," Oppermann says. Predictive cruise CatalIST employs an advanced predictive cruise control that analyzes the upcoming terrain and continuously calculates the most efficient speed and gear for optimal fuel economy. "If we know that a hill is coming in the future, we can support that by precon- ditioning 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 efficiency feature beyond keeping fluids at a cool operating tem- perature, that's hardly the case. CatalIST will cruise at 65 mph using only 80 hp. Yet turning on a fan for a 13-liter engine can consume an extra 50 to 70 hp, depending on engine speed. "You'd basically be doubling the amount of horsepower you need [to run the fan], so you want to minimize that activity," Oppermann says. In CatalIST's fuel economy runs held in near-100-de- gree weather, the fan never came on. e likelihood of seeing a produc- tion-model CatalIST is something south of zero percent, but there are many potential gains to be made by bringing to market production-viable components from this rolling proving ground. While every Class 8 OEM produced a Super Truck under the DOE program, CatalIST is the only one that completely shed its mirrors, relying instead on cameras. Segmented Wabash skirts, which flare inward as they reach the end of the trailer, helped reduce drag by more than 30 percent.