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The use of DPFs will add cost and possibly expand the engine footprint. "We do not see DPFs being utilized on Tier III engines," says Laudick. "However, looking forward to Interim Tier IV, DPFs will most likely be utilized to meet off-highway emission regulations."

"For Tier IV, we will need aftertreatment devices; there is no question about that," Sauerteig agrees. Engine size will likely affect which device is used. "There are many different types of devices, from the very passive catalytic converter to a very sophisticated SCR system. The SCR will use urea injection into the exhaust system. From what we see today, there is going to be a need for SCR on the bigger engines." But he is quick to add that this can change as new technology emerges.

Performance gains?
Engines designed to meet current Tier III emissions regulations are more efficient than the previous generation.

"Certainly, there is a performance improvement by the introduction of electronic controls on the engines," says Sauerteig. "As we go down the road to Tier IV, with all of the aftertreatment devices, it is very difficult to predict whether there is going to be a performance gain. There may be some areas where you see a gain. It is going to be a higher cost for the owner for sure."

Laudick asserts, "We are confident that we will be able to offer performance gains with off-highway emissions technology going forward. However, these gains will be accompanied, in many cases, by higher cost to the OEM and end user for engines and any associated aftertreatment technologies required to meet future emissions regulations. In addition, the cost of engine and vehicle maintenance for the different levels of technology will undoubtedly increase, as well."