Don't Fear Tier 4

Engine technology is getting more complex and costly in the drive to meet stringent emissions requirements; but overall performance gains can still tip the scales in favor of that new equipment purchase. Besides, this technology may actually be required on some jobsites.

Do you plan on bidding work in urban areas? “Contractors who operate in non-attainment areas, which include most major metropolitan regions, may need to utilize equipment powered by an Interim Tier 4 engine,” says Doug Laudick, product planning manager, John Deere Power Systems. “The impact on contractors in non-attainment areas is significant and requires that the engines in their equipment be upgraded to comply with local regulations.”

The primary ways to achieve compliance include retrofitting an existing engine with an aftertreatment device; repowering an older piece of equipment with a newer engine; purchasing new equipment; or renting an emissions-compliant machine.

“Although purchasing new equipment with the latest certified engine usually carries the highest immediate capital expenditure, this option ensures that the equipment is compliant with the latest emissions standards, and is sometimes the best long-term financial decision for the equipment owner,” Laudick asserts.

Building off existing technology

Much of the concern surrounding Tier 4 centers on the unknown. Building off existing technologies minimizes the potential risk posed by a “clean sheet” design.

The use of proven technologies should bode well for performance. For instance, John Deere’s Interim Tier 4 engines continue to use many of the same technologies as its Tier 3 models.

“Our Interim Tier 4 technologies have enabled the PowerTech PSX 6.8L and PSX 9.0L engine models to achieve increased power density over their Tier 3 predecessors,” says Laudick. “Such improvement may allow some applications to transition to an engine platform with a smaller displacement — a change that would reduce purchase price, while delivering similar or greater performance, improved fuel economy and a smaller package size.”

Many gains can be attributed to advanced electronic controls needed to control emissions. “John Deere’s engine control unit (ECU) enables its Interim Tier 4 engines to have full-authority electronic controls, while providing twice the RAM, double the processing speed and four times the program memory of the previous Tier 3 version,” says Laudick. “This allows John Deere’s electronically controlled Interim Tier 4 engines to have a more integrated emissions solution.”

With advanced electronics come other potential benefits. “A beneficial new feature available with electronically controlled John Deere Interim Tier 4 engines is a factory-integrated variable-speed fan drive,” Laudick notes. “The variable-speed fan is controlled by the ECU, enabling it to adjust to engine speed, load and ambient conditions and operate at the slowest speed required to provide proper cooling. Variable-speed fan technology enables equipment to meet new not-to-exceed (NTE) emissions regulations associated with Interim Tier 4, while improving fuel economy and performance.”

Many companies in the on-highway market — which must meet emissions levels equivalent to Final Tier 4 — have moved to selective catalytic reduction (SCR) technology in addition to exhaust gas recirculation (EGR) and diesel particulate filters (DPFs). However, the majority of off-highway OEMs continue to rely on EGR technology with DPFs for Interim Tier 4. SCR requires the addition of a diesel exhaust fluid (DEF) tank. The DEF is injected into the exhaust stream and reacts to the catalyst.

John Deere is among the companies that continue with an EGR-based solution for Interim Tier 4. “The single-fluid approach of our cooled EGR technology means owners and operators won’t have to incur the cost of diesel fuel plus the additional cost for a second fluid (DEF) required by SCR systems,” says Laudick. “While SCR is an effective technology for reducing NOx, it also requires that the vehicle or machine be fitted with a separate DEF tank, a sophisticated DEF injection system and a tamper-proof diagnostic system.”