Why Are New Wheel Loaders Seeing More Fuel Efficiency-Part 1
Date:Jul 06, 2017
For most machines, Tier 4 Final fuel efficiency gains are around 5 percent. Yet fuel efficiency for wheel loaders is up 20 percent and more. How is that possible?
There’s not some magical technology applied to wheel loaders that’s yet to be rolled out to other machines. In fact, every technological advance on wheel loaders can be found on other machines.
What made wheel loaders especially suitable for huge gains in fuel efficiency was their use patterns. “Wheel loaders use their wheels as much as their hydraulics,” says Stefan Salomonsson, product manager, wheel loaders, Volvo Construction Equipment. “This makes their use patterns unique. Other machines don’t have as much opportunity for improvement in fuel usage.”
Mike Stark of Doosan emphasizes that the enabling technologies are the same on wheel loaders as on other machines: programmable engine control units (ECUs), transmission and hydraulic system design improvements and the use of a single overarching electronic “hub” to oversee operations (Doosan calls theirs a “Vehicle Control Unit,” or VCU). “Wheel loaders were especially ripe for improvement because of they have lots of travel, lots of charging the pile and lots of lift, travel and dump. Most other equipment is biased toward a single operation.”
Among the many technologies used in wheel loaders and other equipment, two stand out.
Any new wheel loader can be used to illustrate the role of modern hydraulics; we’ll use Komatsu’s WA270-7. Its hydrostatic transmission has a single pump driving two motors that transfer power to the wheels via a mechanical system. Traction control is part of the system. On the WA270-7, the traction control includes a setting giving the machine’s computer full control of traction to optimize performance and maximize fuel efficiency.
The hydraulic system on the WA270-7 uses a variable displacement piston pump. A variable displacement pump alters flow internally; flow doesn’t rely on engine speed. The engine can run slower, enhancing fuel efficiency with no loss of hydraulic performance. The pump on the WA270-7 has a closed-center, load-sensing design to enable quick and continuous response of the hydraulic system to changes in load.
Hydraulics also control the variable geometry turbocharger (VGT) and the variable speed, auto-reversing cooling fan.
Controller area network bus (CAN bus) systems have been around for a while, but the number of electronic systems has grown past what a CAN bus can handle well. Beyond engine, transmission, and hydraulics, today’s wheel loaders also have multiple user-selectable performance settings, telematics to gather and relay information in real time, and multiple sensors to monitor such things as wheel slip. Higher-level electronics are required to manage all these features.
Liebherr’s answer is Master 4. With 64-bit architecture and large memory, Master 4 has the speed and capacity required to manage a wheel loader’s full complement of electronics, including the CAN bus and the Liebherr Power Efficiency system that optimizes the performance of the drive train. “The Master 4 is the main computer system responsible for integrating all machine components in a single system,” says Ana Cabiedes-Uranga, marketing and communications manager.
Kawasaki’s IntelliTech system manages several subsystems. IntelliDig balances rimpull and hydraulic digging force. SimulLoad coordinates lift and tilt while digging. QuickCycle speeds V-loading cycles. IntelliTech also improves transmission performance. Shift points can be altered to match working conditions. A downshift switch enables faster downshifts while a shift hold button maintains the present gear. AutoMode offers automatic operation in gears 1 through 5 or 2 through 5 as well as a manual mode. Declutching is seamless on level or sloping ground.
Impact on O&O costs
Changes in wheel loader design and operation will have an effect on owning and operating costs. How much? “The impact on a customer’s O&O cost will vary depending on whether the customer is upgrading from older equipment (Tier 3 or before) or newer equipment (Tier 4 Interim),” says Lucas Sardenberg, wheel loader marketing consultant for Caterpillar. “If you look back to Tier 3 units and before, emissions compliance came at the cost of fuel efficiency. A customer upgrading from a Tier 3 machine to a Tier 4 Final will see up to 25 percent better fuel efficiency, partially offset by additional cost for DPF servicing and DEF consumption. A customer migrating from a Tier 4 Interim model to Tier 4 Final will see better fuel efficiency that in most cases more than offsets the additional price for DEF. A good tip for all customers is to make extensive use of telematics to track costs.”
Some changes to O&O costs are subtle. “For example,” says Cabiedes-Uranga, “there is almost no brake wear due to the self-braking action of the hydrostatic drive. At the same time, there is also 20 percent less tire wear since the continuous traction control of the drive line minimizes wheel spin.”
John Chesterman, product marketing manager for production-class wheel loaders with John Deere, says auto-idle shutdown will also affect costs. “Customers need to understand that hourly fuel consumption goes up because if the loader is running, it’s working. But overall consumption goes down because you’ve eliminated fuel wasted during unnecessary idling.”
Residual value is also affected. “A big part of the residual value equation is the ability to export machines,” says Salomonsson. “This continues to have high variability due to the availability of ultra low sulfur diesel fuel in other countries.” Some equipment can be “de-tiered” and made to run on non-ULSD fuel. Some countries are moving to ULSD. Some machines are simply incompatible with a large part of the export market. These factors greatly influence the resale value of equipment.
Stark says Tier 3 machines got a bump in residual value because “some customers don’t want to mess with DEF or were put off by the higher initial cost of Tier 4 models.” He says given the many advantages of Tier 4 equipment, including fuel efficiency, those machines should hold their value well.