It is a dynamic environment for anyone involved in the manufacture or use of diesel-powered equipment. The Environmental Protection Agency (EPA) has been tightening the noose around diesel emissions, with an emphasis on NOx and particulate (PM) matter reduction.
The regulations are phased in over time on a Tier system based upon engine horsepower ranges. (See Table 1 for Final Tier IV implementation.) "Generally speaking, the higher the horsepower, the more stringent the emissions regulations and the more technology needed," says Doug Laudick, manager of product planning, John Deere Power Systems.
In the past, the implementation of each tougher set of standards has resulted in more efficient engines. "Power and productivity generally improved from Tier II to Tier III," says John Bartz, wheel loader and articulated hauler product portfolio planning, Volvo Construction Equipment.
Laudick agrees, noting, "When John Deere transitioned from Tier II to Tier III, most engines realized significant performance gains."
The final verdict on whether Tier IV will continue this trend has not yet been determined. One factor that could influence performance is the mandated move to ultra-low-sulfur diesel (ULSD) fuel, which typically has a lower British Thermal Unit (BTU) energy content.
"As we move to ULSD fuel, we will all see the resulting fuel consumption increase," says Bartz. "Volvo is working with the available engine technologies to reduce this impact and improve overall efficiency. Along with engine technology, various machine systems are also being looked at to improve efficiency."
Cummins has already announced the technology it's going to use to meet Interim Tier IV regulations and has been testing these products, according to Jennifer Rumsey, technical project leader, Cummins Inc. "The 174- to 751-hp product range will maintain or increase power outputs compared to Tier III," she states. "Fuel efficiency will improve by up to 5%, depending upon rating and duty cycle."
Similarly, John Deere expects to offset any performance penalties for the ULSD. "While the performance of our Interim Tier IV engines has not been finalized, we anticipate performance and fuel economy will be similar to Tier III while meeting the more stringent Interim Tier IV emissions regulations," says Kevin Resch, manager of product planning for Tier IV.
Influence of on-road technology
The current generation of on-road diesel trucks provides a pretty good glimpse of what you can expect to see in terms of technology to meet non-road Tier IV regulations.
"The same technologies used for on-highway engines will continue to trickle down into non-road products," says Resch. "However, one of the biggest challenges is the rate at which these technologies - originally developed for on-highway use - must be adapted for non-road use.
"The time between adoption of a new technology for on-highway engines and its use in off-highway applications has continued to decrease," he continues. "Off-highway equipment often works in harsher, more varied environments. Additional development time is required to make on-highway technologies suitable for off-highway applications. Ensuring the robustness of these technologies for off-highway use will continue to be a challenge through Final Tier IV."
Rumsey agrees the solutions must be customized to meet the unique needs of the off-road environment. The Cummins particulate filter serves as an example. "We considered the high shock loads, angularity and space restrictions in the off-highway environment," she asserts.
Moving to Tier IV
The step from Tier III to Interim Tier IV will require new technology in the form of aftertreatment devices - catalyzed diesel particulate filters (DPF) that will replace conventional mufflers. Some companies will continue to build on Tier III solutions, while others are coming up with unique solutions to address Tier IV.
"Volvo, in large, utilized EGR to address the Tier III challenge," says Bartz. "There are a number of technologies being considered for Tier IV, one of those being aftertreatment.