Off-road diesel engines have made significant strides since the Environmental Protection Agency first adopted Tier 1 emission standards in 1994. Tier 4 standards have been phased in since 2008, with the strictest Tier 4 Final requirements to reduce nitrogen oxides and particulate matter incorporated last year and this year.

However, Tier 4 Final standards are outcome-based, not prescriptive — each manufacturer is permitted to achieve outcomes using its own solutions and technology. On hand to discuss their approaches are: Joe Mastanduno, account manager, Rental Marketing, with John Deere’s Construction and Forestry Division, and Brad Stemper, solutions marketing manager with Case Construction Equipment.

MSW: What differences will operators see in off-road vehicle engines in Tier 4 Final?

Stemper: Selective catalytic reduction (SCR) has allowed manufacturers of excavators and other machines to meet the NOx standards of Tier 4 Final most efficiently. Our excavator solution involves a more efficient SCR system in combination with a diesel oxygen catalyst that uses a chemical process to break down particulates into less harmful components, reducing overall emissions by up to 95 percent. We didn’t want to stack up technologies that could use more fuel, affect peak horsepower or force us to redesign the machine envelope for technologies that would adversely affect our purchase prices, particularly on small- to medium-sized equipment.

Mastanduno: Our approach at John Deere has been to build on proven technologies, including cooled exhaust gas recirculation (EGR), exhaust filters, and variable-geometry turbochargers. We refer to this as the building block approach. Particulate matter levels established in our Interim Tier 4 designs will be maintained while NOx will be further reduced by about 80 percent. This NOx reduction will drive the need for a new technology called SCR to be added to engines above 75 hp. This technology will require an additional fluid called diesel exhaust fluid (DEF), therefore a tank, lines, pump and nozzle are all new components associated with Tier 4 Final. Due to the continued usage of cooled EGR, the DEF consumption will be quite low which allows for smaller DEF tanks and lower DEF costs.

MSW: How do these changes benefit users?

Stemper: Users don’t care about how Tier 4 Final is being resolved. They want a machine that runs the same, offers the same or better efficiency, costs less, and earns them more money. We used the emission mandate as an opportunity to improve our machines. For example, we looked at ways to integrate hydraulics and electronics to create a variety of work selection modes and make the machines more efficiently leverage movement and stored power.

Mastanduno: Aside from the obvious benefit of lower engine emissions, John Deere has worked to provide additional benefits as well. A great example of this is in the telematics, which create the ability to monitor engine performance remotely, diagnose any problems and report them to the owner. We can also update diagnostic software remotely and seamlessly using our exclusive communications tool, JDLink.

MSW: Have Tier 4 Final engines sacrificed any power?

Stemper: Power hasn’t been sacrificed between Tier 4 Interim and Tier 4 Final because power range is still a deciding factor in purchase. On earlier versions, we reaped the efficiencies of going electronic, using high-pressure common rail fuel delivery and increasing performance with reduced engine size, so we haven’t sacrificed horsepower with Tier 4 Final.

Mastanduno: People aren’t willing to sacrifice power or torque. Through all of the changes, the power and performance of our engines have remained the same with no degradation in reliability, responsiveness or ease of operation.

MSW: Are there any increased requirements for maintenance?

Stemper: The SCR system found in our new excavator line requires the use of DEF. However, as a whole the equipment is migrating to a longer life cycle, longer time between oil changes, and longer service intervals. There’s no diesel particulate filter that needs to be changed, and no related regeneration.

Mastanduno: The exhaust filter is integrated into the engine design, which continuously regenerates and cleans it during normal engine operation without operator involvement. The initial EPA requirement was that diesel particulate filters needed to last 3,000 hours before ash removal. We’re now up to 10,000 to 15,000 hours, which is often the life cycle of construction equipment before people retire or sell their machines. Operators will now have to change a small DEF filter along with routine maintenance.

MSW: Have users become more savvy about maintaining supplies of DEF?

Stemper: The industry has adapted to that, primarily because the trucking industry drove demand before off-road requirements were phased in. Customers in remote locations are now seeing fuel delivery trucks carrying DEF. As Tier 4 Final becomes applicable to vehicles with lower horsepower, we’re now seeing a brand-new customer base being exposed to the need for DEF for the first time — owners of skid-steers and backhoes, and small landscape companies, for example.

Mastanduno: Fueling companies have adapted well to the market needs and they’re routinely supplying DEF along with diesel fuel. DEF can be purchased in numerous ways ranging from simple 2-gallon jugs to bulk delivery.

MSW: Any new engine monitors or alarms?

Stemper: One change is that some systems no longer require operator intervention. For example, the SCR technology doesn’t require the operator to regenerate the system. In short, there are fewer bells and indicators in our Tier 4 Final.

Mastanduno: We’ve added sensors and monitors to the equipment, but we didn’t want to add flashing lights just because something is happening. Do you need to see a light flashing when a filter is going through a self-cleaning cycle? Manufacturers struggle with the right level of information to provide the operator, and we will only flash a light when it’s something that requires action from the operator.

MSW: Does Tier 4 Final offer retrofit possibilities?

Stemper: Today’s engines are very complex, from electronic engine management, to exacting exhaust pressures entering the catalytic chamber and leaving it. To retrofit, you not only have to add equipment, but understand how it works with every other part of the engine, and then go through the process of finding a way to monitor it. I would say it is difficult and becomes cost-prohibitive to the owner.

Mastanduno: Retrofitting will continue to be an option for those who own older machines and have a need to bring the emissions up to a higher standard than what they were originally designed to meet. This need is often tied to certain contracts or local air-quality requirements. At this time the retrofits John Deere offers will improve both PM and NOx emissions but generally are not capable of achieving Tier 4 standards.

MSW: The EPA is always looking to the future. What could Tier 5 look like?

Stemper: Europe is currently looking at implementing standards for CO2 exhaust emissions. We’re hearing rumblings in the industry that this might be introduced in North America, but nothing has been formally decided yet.

Mastanduno: If it does happen, we might see attention paid to smaller particulates or fuel consumption controls. However, for off-road vehicles, setting a standard for fuel consumption could be very difficult. How do you measure the fuel efficiency of a skid-steer against the efficiency of a motor grader?