Overdrive Magazine | Trucking Business News & Owner Operator Info
Issue link: http://read.dmtmag.com/i/856429
August 2017 | Overdrive | 57 noise because there was none. Another distinct feature: An air-over-leaf suspension drops the front of the truck and rear of the trailer for an airfoil shape – picture the cross-section of an airplane wing – across the top of the combination when it hits 50 mph. "On the expressway, you're not expecting to see curbs or bumps, so having it as low as possible is a good thing," Oppermann says. "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, which is exactly what you want," he says. "It's a little bit the best of both worlds." You can't necessarily feel this while it's happening. But you notice it when it's com- plete, as the driver's seat feels ever so slightly tilted forward. Using a 6x2 axle was low-hanging fruit in terms of boosting fuel efficiency, 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. The oppo- site happens at 50 mph, when ride height changes. The weight is biased to the tag axle to take advantage of its lower rolling resistance. CatalIST's engine is a base International A26 with upgrades to help achieve a high rate of converting the fuel's heat to mechanical ener- gy, 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 transmis- sion. 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 weight savings and improved aerodynamics give the truck an effortless and slippery feel on the road. The lack of wind resistance translates into a reduced need for power that's noticeable by simply peeking at the tachom- eter. 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, even though it revives immediately when you tap the accelerator. CatalIST also has a 48-volt kinetic energy recovery sys- tem. A 15kW motor generator 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 compres- sor and a no-idle sleeper unit. Equipped with the 48-volt system and with electric ener- gy at its disposal, the entire HVAC system was convert- ed to fully-electric. "That's important because when the engine shuts off, it won't affect the interior," Oppermann says. Predictive cruise CatalIST employs an advanced predictive cruise control that analyzes the upcoming terrain and con- tinuously calculates the most efficient speed and gear for optimal fuel economy. While such systems have been in use for years, this one prepares the engine for the imminent changes. "If we know that a hill is coming, we can support that by preconditioning the engine," Oppermann says. "We can speed up the water pump and bring that tempera- ture 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 oper- ating temperature, 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 dou- bling the amount of horse- power you need [to run the fan], so you want to minimize that activity," Oppermann says. In CatalIST's fuel econ- omy runs held in near-100- degree weather, the fan never came on. The likelihood of see- ing a production-model CatalIST is something south of zero percent, but there are many poten- tial gains to be made by bringing to market pro- duction-viable components from this rolling proving ground. While every Class 8 truck maker pro- duced 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 trail- er, helped reduce drag by more than 30 percent.