Farm Progress

Next-Generation Engines

Diesel engine manufacturers continue to make refinements to their products to meet the EPA's ongoing emission requirements.The latest of these is Tier 4, which calls for a 90% reduction in the levels of harmful gases, like oxides of nitrogen and particulate matter, set in Tier 3.Deadlines to meet Tier 4 requirements vary by horsepower class. Non-road diesel engines rated 174 hp and higher, a size typical on Midwest farms, face an interim deadline of 2011 and a final deadline of 2014. 

Jodie Wehrspann

February 1, 2009

9 Min Read

Last March John Deere's non-road diesel engine group announced the technology it will use to reach the near-zero emission levels set by the EPA. Diesel engines have gone through a few tiers, and the last level, Tier 4, is the toughest yet. It calls for a 90% reduction in the levels of harmful gases, like oxides of nitrogen and particulate matter, set in Tier 3.

Deadlines to meet Tier 4 requirements vary by horsepower class. Non-road diesel engines rated 174 hp and higher, a size typical on Midwest farms, face an interim deadline of 2011 and a final deadline of 2014. (See “Reinventing the Engine,” August 2008.)

Deere has shared little about its engine plans since the March announcement. But in a recent exclusive interview with Farm Industry News, Steve Meinzen, Deere's manager of integration of Tier 4, talked in detail about the characteristics of the company's Tier 4 diesel engine and how the engines will change tractors and combines.

Combustion basics

To fully understand the challenge that engine makers, like Deere, face, it helps to review the basics of combustion. When air is compressed, it heats up. Internal combustion engines like diesels compress air until it is hot enough to ignite with fuel. When fuel burns or “combusts,” it creates energy. In farm vehicles like tractors and combines, the energy is used to power the wheels and pull implements like planters, balers and tillage tools.

The most efficient combustion is when all fuel is burned. However, complete combustion is rare because engine conditions must be perfect. Changing speeds and field conditions make it difficult for air and fuel to mix at the right ratio, and the result is unburned fuel. Fuel left unburned turns into lung-clogging soot, called particulate matter (PM), and noxious oxides of nitrogen (NOx).

Thermal vs. chemical

There are basically two ways to eliminate the by-products of unburned fuel, Meinzen says. “If unburned fuel makes its way through the engine in the form of black smoke or particulates, the best way to get rid of it is to, one, trap it on a filter, and two, thermally get rid of it by increasing the exhaust temperature to 300 to 1,000°F and burn it off,” he explains.

Deere will use a diesel oxidation catalyst (DOC)/diesel particulate filter (DPF) to trap unburned particles and incinerate them before they exit the exhaust. This ceramic unit is coated with special metals that catalyze harmful by-products and turn them into clean exhaust emissions, namely nitrogen, carbon dioxide and water.

Meinzen says the DOC/DPF unit is similar to catalytic converters used in cars since the 1970s. “When you first start your car, especially if it's cold, the engine isn't hot enough to achieve complete combustion, so not all the fuel gets burned,” he explains. “Once the car warms up, the unburned fuel trapped in the catalytic converter is heated with the hotter engine exhaust temperature and cleans up the exhaust gases.”

In addition to the DOC/DPF unit, designed to get particulates, Deere will use an Exhaust Gas Recirculation (EGR) system to get the NOx. Recirculation systems cool the exhaust air and recirculate it to prevent their formation. NOx forms when engine temperatures are too hot. Deere already uses EGR technology in its Tier 3 engines. But to meet the stricter limits set for Tier 4, it will use a higher percentage of cooled exhaust gas.

While EGR and DOC/DPF use thermal means to reduce emissions, Meinzen says the same changes can be made chemically through a process called Selective Catalytic Reduction, or SCR. With this process, air is cleaned by introducing an additive like urea to scrub the exhaust air clean after combustion. Deere considers SCR a Final Tier 4 solution, not an Interim Tier 4 (IT4) solution. EGR is a proven technology for heavy-duty off-road applications for IT4 and avoids the cost of another fluid, urea, which would require regular refills and a dosing system and freezes at temperatures below 15°F.

SCR takes care of the NOx by introducing urea, or NH3, at the very end of the exhaust stream. When NH3 is combined with nitrate oxide (NO2), the chemicals break down into harmless nitrogen, carbon dioxide and water. “So it gets back to high school chemistry class that most of us tried to avoid,” Meinzen says. “Simple chemical reactions.”

John Deere says it chose the EGR and DOC/DPF technology path to meet IT4 standards because it is proven, simpler, and less costly to operate than the alternate NOx reduction technology of SCR. However, short of a technological breakthrough, Deere, along with others in the industry, say farm vehicle makers will have to use both solutions to meet the emission reduction levels called for in Tier 4 Final.

Good, bad, ugly

So what do all these engine changes mean for tractor buyers? Meinzen gives the play-by-play on what the IT4 upgrade will mean:

Same look

Visually, you won't notice much. Deere's IT4 engines will result in few changes from a tractor design standpoint. “Probably the most noticeable change will be the muffler,” Meinzen says. The DOC/DPF device used to incinerate particulates will actually replace the muffler but will be three times the size. Meinzen says you probably won't notice it on combines because of its positioning. But on tractors it will be obvious.

A second turbocharger will be added to larger engines to help maintain efficiency when duty cycles vary. “We are looking for a very efficient burn process,” Meinzen says. “Not all engines but some of them will receive dual turbos to handle varying loads from zero up through full.”

Engines also will be equipped with a crankcase ventilation system to manage crankcase emissions. IT4 regulations state that crankcase emissions must be managed via a crankcase filter or counted in the total engine emissions.

Price challenges

Meinzen says the biggest challenge will be to deal with the increased cost to implement this new technology. He says the after-treatment components will add to the price of tractors. “The EPA's estimate has been 2 to 3% of the vehicle cost,” he says. “We believe that is too low and are working hard to keep costs down while meeting the new emissions regulations.”

The price increase is expected across the board because all manufacturers will have to buy the same after-treatment components, which are expensive. “Precious metals are just one example,” Meinzen says. “Palladium and platinum essentially come from only two places in the world: South Africa and Russia. Even though these metals are applied in just a very thin wash coat over the after-treatment parts, they are a still a major cost driver that all of us will have to use in the cleanup.”

As part of the cleanup, the EPA is requiring that sulfur in diesel fuel be reduced to 15 parts per million. (Sulfur corrodes the metals used in the after-treatment devices.) Meinzen says that in turn will drive up fuel prices but will result in a cleaner-burning fuel. “It's just like with cars,” he says. Just as lead had to be removed from gasoline, sulfur has to be removed from diesel fuel to prevent the corrosion of the emission control devices.


“You are not going be able to do the things you normally do if you are a tinkerer,” Meinzen says. Farmers will still be able to change oil and air filters, but will not be able to replace components such as fuel injectors and nozzles.

As a result, dealers will have to do most of the maintenance on IT4 tractors. “Disconnecting things will create fault codes just like it does on a car and may even disable the vehicle,” Meinzen says. “So unless you're trained, you won't be able to fix the problem.”

Longer maintenance intervals

Because the engines are cleaner, less maintenance will be required and the intervals between maintenance will be longer than in the past. For example, oil change intervals will almost double (300 to 500 hrs.) because the engines run cleaner. “Farmers will be able to go two seasons before needing to change oil,” Meinzen says. “This is a fundamental shift because the engine and oils will be much cleaner and the combustion process much better.” This also will mean there will be less used oil to dispose of.

Better performance

What's more, the engines themselves will be more durable than current engines. And the engines will be very efficient due to a controlled-combustion process.

Just as fuel efficient

Deere maintains that its IT4 engines will be every bit as fuel efficient as its Tier 3 tractors, which hold the record for being the most fuel-efficient tractors, according to tests at the Nebraska Tractor Test Lab (see “The most fuel-efficient tractors,” November 2008).

Meinzen says fuel efficiency also depends on how customers operate the vehicle (see “Three ways to save fuel,” page 50).

The bottom line

In the end, the switch to more efficient Tier 4 engines will result in a situation similar to the one in which the EPA mandated catalytic converters on cars, according to Meinzen.

“IT4 is one of those things mandated on manufacturers, just like the catalytic converter,” he says. “When we bought cars with converters on them, there was a price increase that came along with it. Fuel efficiency has actually gotten a little better since then. And we do less maintenance on our own vehicles. Now we don't even change spark plugs for 100,000 miles. So this is similar to what is going to happen with tractors.”

Yes, buyers will pay more for the engines. But the trade-off is cleaner air, just like it was with the catalytic converter. “People didn't quit buying cars just because they had a clean air device on them,” Meinzen says.

Deere will make sure its customers see the value of these new engines. Starting this spring, the company plans to offer training meetings for dealers. One topic covered, for example, will be how to optimize fuel efficiency using new technology like assisted steering and remote vehicle management systems. Another topic will be how to match the vehicle to the task.

Deere ultimately wants its customers to realize more savings than the cost of the EPA-mandated emission controls. It will do this by helping customers become more proficient tractor operators and by applying new technology.

“Our goal is to make sure that enough value is there so that at the end of the day, the customer will say, ‘Oh by the way, it is IT4 compliant,’” Meinzen says.

For more information about the engine rules, regulations, and technical terms, contact your local John Deere dealer.

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