Steve Slesinski, director of product planning for the commercial-vehicle market at Dana Holding Corp. directs the development and implementation of global axle product line strategies while supervising product management to meet current and future market needs. He has served in various engineering, program management, planning, and strategy positions for over three decades. His experience includes the development of axles, brakes, driveshafts, transmissions, tire management systems, and trailer air suspensions.
Q: From what truck OEMs are saying, the next round of GHG/MPG standards will require even more innovation on the part of component suppliers. Which components will likely make the greatest contribution to further improve fuel efficiency and what engineering advances will come into play?
A: We typically start by looking at places where we can help reduce energy losses, and the engine is responsible for approximately 60 percent of those losses on today’s trucks. We expect that increasing engine efficiency will continue to be the area where truck manufacturers and suppliers will focus most of their efforts. Modifications in the operation and performance of the engine affect every other component all the way through the drivetrain.
This is why we continue to work closely with engine and transmission manufacturers to engineer durable, reliable driveline components that integrate effectively with the rest of the system to properly enable engine downspeeding. Aerodynamics can contribute nearly a quarter of energy losses for trucks traveling at highway cruise speeds. Gap, underbody and tail devices for reducing drag are relatively inexpensive and can deliver immediate benefits.
While the drivetrain typically accounts for less than 6 percent of energy losses, we are continuously developing ways to improve overall mechanical efficiency. This includes further optimizing the gear design, reducing internal friction, and engineering the carrier housing to distribute lower volumes of lubricant while doing so more effectively— all while maintaining reliability and reducing maintenance costs.
Q: What’s the status of the Spicer AdvanTEK Dual Range Disconnect “concept” for tandem axles on linehaulers that was presented at MATS in 2015? Is there any plan yet to bring that into production?
A: We are currently in vehicle trials as we continue to tune and develop the Spicer AdvanTEK Dual Range Disconnect tandem axle. We’re working side-by-side with certain truck manufacturers to integrate this axle with a number of advanced engine and transmission combinations to achieve optimal performance and efficiency results. It’s important to note that our patented dual-range disconnect technology allows OEMs to further reduce engine rpms at highway cruise speed far below what is available today.
While traditional engines cruised at 1350 rpm and today’s downsped engines reduced those cruise speeds to as low as 1125 rpm, the next step down will be in the 1080 rpm cruise range, with our dual-range disconnect tandem axle enabling engine speeds as low as 900 rpm at highway cruise. These development efforts are in response to our fleet customers and Phase 2 greenhouse gas emissions standards and fuel efficiency standards, which will require higher truck efficiencies in the 2021 and 2024 model years.
As truck manufacturers pursue more aggressive engine downspeeding efforts to meet these new standards, the Spicer AdvanTEK Dual Range Disconnect tandem axle is planned to be ready well in advance of these new trucks rolling out in 2020.
Q: Downspeeding is recognized as a fuel-saver, but as I understand it, it’s not an approach that can be taken willy-nilly lest drivetrain failures result from increased torque. How do you explain what downspeeding is all about?
A: Engine downspeeding is not a reduction in the size of the engine; instead, it’s a reduction in the rpm of the engine, especially at highway cruising speeds typically between 55 and 70 miles per hour. Downspeeding allows the engine to cruise in its sweet spot for optimal fuel conservation, reducing friction, increasing fuel efficiency, and reducing carbon dioxide emissions.
Where most truck engines previously ran at around 1350 rpm at highway cruising speed to provide the power needed at the wheel end, engine downspeeding allows the truck to operate consistently in a more efficient range, generally between say 1100 to 1200 rpm, while maintaining the same power at the wheel end.
An engine running at lower rpms requires faster axle ratios to maintain the same vehicle speed and performance in all driving conditions, and this generates significantly higher torque stresses in the drivetrain. These higher torques place added stress on the axle, driveshaft, and inter-axle shaft, requiring more robust gearing, bearings, and U-joints to maintain expected performance and life of the system.
A powertrain that takes advantage of the efficiency gains from engine downspeeding requires all elements– engine, transmission, axle, and driveshaft– to work in concert to deliver the power needed to get the job done with the maximum efficiency and reliability.
In summary, engine downspeeding reduces the rpm of the engine at highway cruise speeds, requiring lower numeric axle ratios and decreasing the speed of the driveshaft. Since there is now less gear reduction in the drive axle, the amount of torque in the driveline must increase to enable the vehicle to maintain the desired power at the wheel-end.
Q: In February, at TMC, Dana said it now offers axle ratios compatible with all seven configurations of the Cummins/Eaton SmartAdvantage powertrain. How do axle ratios contribute to powertrain efficiency and performance— and with the degree of powertrain integration now being seen, is it the OEM or the fleet that now specs the axle ratios?
A: By collaborating with Cummins and Eaton, we can develop rear axle ratios to keep engines running in their sweet spot for fuel efficiency for the majority of the intended vehicle duty-cycle.
Lower numeric axle ratios allow engines to run at lower rpms at highway cruise speed, while higher axle numeric ratios improve vehicle performance, enhancing maneuverability while reducing the likelihood of high torque spikes and overall lower driveline torque at cruise speed.
There are tradeoffs in performance and fuel efficiency depending on the axle ratio a fleet selects. When choosing an axle ratio to improve startability, gradeability, and low-speed maneuverability, you sacrifice fuel efficiency at highway cruise speeds. By the same token, if an axle ratio is selected to optimize fuel efficiency, then relative performance can be negatively impacted.
Many OEMs specify engine-transmission combinations that provide fleets some flexibility in the selection of an axle ratio, and Dana offers the most axle ratio options between 2.26:1 and 2.79:1 for fleets looking to take advantage of engine downspeeding. By doing so, we can fine-tune the rest of the system with the right axle ratio, enabling fleets to find the optimal balance of fuel efficiency and performance for the unique operating conditions they face.
Q: A fuel-saving concept that anyone can easily grasp is “lightweighting.” What is Dana doing to reduce the weight of the components it provides to OEMs without sacrificing durability and performance over the life of the vehicle?
A: Our Spicer AdvanTEK 40 tandem axle is an excellent example of how we are reducing component weight while improving performance. While designed for the faster ratios and higher torque loads associated with engine downspeeding, this axle also weighs up to 37 pounds less that the standard 40k tandem axle.
At TMC, we announced a next-generation driveshaft for engine downspeeding that is 30 pounds lighter than existing products and is tailored to address the specific torque-management strategies of individual commercial-vehicle manufacturers.
Meanwhile, our innovative and robust Spicer E-Series steer axle, which features a unique, one-piece integrated arm knuckle and a new, lighter weight forged steel I-beam, was just launched into OEM production. This axle reduces total weight by up to 69 pounds vs. competitive axles without sacrificing performance.
Dana is looking to help fleets and OEMs reduce weight across all of the vehicle markets we serve, and we are in a unique position to use the knowledge we gain in one market and apply it to others. In some cases, we can offer lightweighting by integrating components, optimizing shapes to reduce mass, and reducing the amount of lubricant needed in our systems. In other cases, we offer benefits that allow for the elimination or the reduction in size of components elsewhere in the vehicle.
Q: No fleet wants to spend more than it has to on fuel, and the GHG/MPG rules are also compelling suppliers to push the fuel-efficiency envelope. And fleets want the lowest maintenance costs possible. And then there's the driver shortage— fleets want to spec trucks that will attract and keep drivers. Is there a balancing act that component suppliers have to be adept at to deliver on all these needs?
A: Fuel efficiency, driver performance, and durability are very much interconnected, and we are actively finding ways to strike the right balance. By developing technologies that help make trucks as efficient as possible, we keep fleets running while making it easier for drivers to meet their fuel economy goals. However, fuel efficiency is not an engineering exercise, as fleets and drivers only get paid when payloads reach their destinations. Reliability and durability are primary considerations to properly enable greater fuel economy.
Further contributing to fleet reliability and durability is our Spicer Optimized Tire Pressure Management System. Currently in fleet trials, this technology will automatically maintain proper tire pressure to further maximize fuel economy, reduce tire wear, improve vehicle uptime, and reduce the demands on the driver to check and adjust tire pressure.
Bringing systems to the market that help fleets and drivers meet productivity expectations are paramount to our industry.
Q: Before we leave off, I want to ask what first drew you to your career path— engineering, marketing, or just getting to be around trucks?
A: I grew up in the Detroit area, right in the heart of the automotive capital of the world. My grandfather, father, aunts, uncles, and cousins all worked in the automotive industry, and from an early age I knew the transportation industry was my career path destiny.
I find it extremely interesting and rewarding to be in the commercial truck business. It’s a close-knit family of good, hardworking, and creative people who join together and implement reliable new technologies that help improve productivity for fleets and OEMs, enabling more than 800,000 truckers to keep the economy moving for all us.