How Tier 4 Final Technology Reduces the Complexity of Meeting Engine Emissions Regulations

Ask any rental professional what keeps them up at night and one of the most common responses is the headache of dealing with Tier 4 emissions regulations. Whether it's the increased cost of the equipment, the maintenance requirements or the potential resale challenges, opinions on this subject are invariably strong. And like all major transitions, adjusting to changing engine technology takes time. 

Tier 4 Final solves most of these problems, with selective catalytic reduction (SCR) being a key enabler. Since PM and NOx inversely impact each other, Tier 4 Interim fought a battle because anything done to improve one created more of the other. SCR solves that problem but adds complexity and cost, so manufacturers held off on its use until Tier 4 Final so as to avoid increasing the cost of engines too dramatically at one time. Today, enhanced NOx reduction through SCR allows for optimized fuel combustion in-cylinder which reduces particulate matter (PM) and can eliminate the need for a DPF. Kevan Browne, Cummins: The transition from Tier 4 Interim to Final has required no significant change to Cummins engines, other than enhancements to the fuel injection and the combustion formula. With the Tier 4 Final regulations focused on reducing only NOx, this was achieved with the incorporation of selective catalytic reduction (SCR) into the exhaust aftertreatment system for engines rated above 74 hp (55 kW).

U.S. EPA Tier 4 Final and EU Stage IV low-emissions regulations for the 75 – 173 hp node took effect on Jan. 1 of this year, requiring new standards for nitrogen oxide (NOx). While a considerable challenge for engine manufacturers, the implementation of Tier 4 Final requirements actually alleviates several of the frustrations associated with Tier 4 Interim technology, such as the need for active regeneration and the issue of plugged diesel particulate filters (DPF).

To find out how the latest engine technology can simplify things for your business, we talked to several leading engine manufacturers. Following is an excerpt from that discussion:

Rental: How has Tier 4 Final technology changed from Tier 4 Interim?

Steve Corley, chief sales officer for Deutz Corporation: In a short period of a few years, engine manufactures were able to understand the challenges faced by operators and develop more robust engines and after-treatment systems by taking the guess work away from the operator so they could focus on their job. The use of advanced engine controls and effective use of sensors has essentially reduced engine emissions to near zero levels on all four constituents (NOx, HC, CO and PM). On engines rated above 75 HP, Tier 4 Final requires us to reduce NOx by 90 percent compared to Tier 4 interim and this has been achieved with the addition of selective catalytic reduction (SCR) systems. The system requires a catalyst and the use of diesel exhaust fluid (DEF). A DEF tank also needs to be fitted in the machine that will require fill ups at appropriate intervals. The machine control panel will have to include additional lamps that indicate when DEF needs to be added. DEF is used on all modern on-highway trucks and is proven technology. One benefit at Tier 4 Final is that our 4-8L engines will now adopt a passive DPF system, meaning it will continuously regenerate and not store PM that needs to be burnt through a regeneration cycle.  

Cummins' approach to installation transition was making our Tier 4 Interim solution "machine adaptive" to meet Tier 4 Final, so that OEMs could more easily make that later change. We designed our Tier 4 Interim aftertreatment as a modular system, able to later incorporate SCR for Tier 4 Final. For our mid-range engines, space was made available by replacing the diesel particulate filter with a smaller, simpler diesel oxidation catalyst (DOC) system.

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