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The future is clear

The diesel engine industry is now in the midst of a three-tiered timeline to meet EPA's guidelines for on-road and off-road emissions standards. The progression began in 1996, targeting nitric oxide (NOx), carbon monoxide (CO), and soot particulate (Pm) components of diesel exhaust. In brief, the EPA wants a nearly 90% reduction of these pollutants by 2007.

To date, the diesel engine industry is largely on schedule for reducing pollution, though there have been some bumps along the way. In 1998, the EPA accused several diesel truck engine manufacturers of violating air-quality standards. At issue was a slick gadget called an auxiliary emissions control device, which changed how engines ran during an emissions test but didn't reduce emissions when the engines were actually operating under load or at highway speed. Caterpillar, Cummins, Detroit Diesel, Mack Truck, Navistar International and Volvo Truck corporations agreed to pay record fines, but denied any wrongdoing.

When it was over, fines and redesign expenses cost the diesel engine industry nearly $1 billion, the largest penalty ever paid for violating an environmental law. And it wasn't really over; in addition to the fines, the EPA cracked down with more stringent rules, accelerating the timeline for reduced emissions on all diesel engines.

The cost to farmers

Because any increase in equipment cost is ultimately passed on to the buyer, several farmer groups claimed EPA had unfairly forced farmers to bear the brunt of clean air standards. According to EPA, diesel emissions produce 28% of the nitric oxide and 2% of the particulate matter polluting the air. EPA's figures also indicate that off-road diesel equipment accounts for more than twice the pollution of on-road diesel sources.

In 1998, EPA wrote additional rules aimed at reducing off-road NOx emissions by about a million tons per year, the equivalent of taking 35 million passenger cars off the road. According to EPA, the cost of meeting the emissions standards should add another 1% to the purchase price of new non-road diesel equipment. However, some industry insiders estimate the figure might be closer to 3 to 5% per tractor.

Just what do you get in your diesel tractor for that extra money? We asked four very different tractor companies how they're meeting the challenge of appeasing the EPA while keeping costs down, power up and air clean.

John Deere's high-tech approach

Deere's new diesel engines achieve lower emissions levels through the use of advanced electronics that precisely control engine power and torque. But that's not all. Other changes include air-to-air cooling, new pistons, electronic unit injectors (EUIs), turbochargers and high-pressure fuel systems.

According to Rick Bishop, John Deere Power Systems manager of environmental compliance, new electronics wouldn't necessarily be required for Deere engines to meet Tier 2 emissions standards. But the company's new electronic control unit (ECU) makes it possible to both reduce emissions and improve performance by providing a precise amount of fuel and correct engine timing. The ECU reduces engine smoke emissions throughout the entire speed and power range. It features self-diagnostic capabilities that can keep a record of engine performance.

Increased use of air-to-air cooling, also known as intercooler technology, makes the new Deere engines run cooler and more efficiently with fewer emissions. The intercooler also increases low-speed torque and engine durability.

Deere uses a variety of fuel delivery systems for its various-sized engines. An electronically controlled version of the standard rotary fuel pump will be an upgrade for 4.5- to 6.8-l engines. The big 12.5-l engines will keep the same electronically controlled unit injector system, which uses the ECU to activate a solenoid and control engine fuel delivery and timing.

The mid-range 8.1-l engines will use something totally different — the high-pressure common rail. Becoming increasingly popular in the diesel engines of European luxury cars, the common rail enables fuel to be injected in the engine's combustion chamber at very high pressure, so fuel and air mix more thoroughly for a cleaner burn. The common rail is essentially a pressurized reservoir next to the cylinder heads. Unlike earlier fuel delivery systems, in which the injection pressure varies with speed, the common rail enables the engine to operate at peak efficiency at any engine speed. Each line receives constant pressurized fuel that's available when the EUI opens.

Bishop says Deere's three-pronged approach of electronic control, intercooling and high-pressure fuel systems will enable Deere engines to meet all EPA Tier 2 requirements. “As for Tier 3,” Bishop says, “EPA is still deciding on the exact requirements for 2006. An add-on exhaust gas recirculator will likely be the primary additional technology needed to meet Tier 3.”

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The world's largest manufacturer of diesel engines for trucks will eventually integrate its pollution control technology into its agricultural diesel engines, too. For the long term, Caterpillar hopes to avoid the quick fix of add-on pollution control devices. According to Caterpillar spokesman Carl Volz, the result will be engines that are cleaner, more efficient and less bulky.

“Any time you have to add on devices, the engine takes up more space and fuel economy suffers,” Volz says. “An exhaust gas recirculation device uses up engine power to push the exhaust gas through additional channels. That's why Caterpillar has chosen to take a total systems approach instead, building a more efficient and cleaner engine from the ground up. Not only does this produce fewer emissions, it results in improved, rather than reduced, fuel economy.”

Citing the need to protect proprietary technology, Volz wouldn't reveal any specific new technologies in the new engines. But he did say the new system, called Advanced Combustion Emissions Reduction Technology (ACERT), combines Caterpillar advances in fuel systems and engine combustion. That means electronics, cylinder size and shape, fuel injectors and the electronic control modules will all work in sync to burn more emissions at the point of combustion.

Volz says that, by 2003, ACERT will be in place for all new on-highway engines built by Cat. The same technology will be part of Challenger tractor engines and other off-road Cat engines by 2006. That schedule will meet and exceed EPA requirements for on- and off-road emissions.

Except for better fuel economy and reduced engine noise (up to 50%), Cat claims the transition to ACERT engines will be almost transparent to customers. And because component changes in the engines will be minimal, truck and farm tractor manufacturers will be able to install the engines just as easily as they could install the old ones.

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Kubota's tight tolerances

Known as the first company to pass California's strict laws for lawn and garden equipment engines, Kubota is putting its know-how to use in larger tractor engines as well. While some companies have turned to complex systems to reduce emissions, Kubota has attempted to stay with the simplest approach possible.

Cameron Larson, Kubota's senior engineer in charge of emissions standards, says that even he is amazed at how efficient and clean Kubota engines can run without resorting to a lot of add-on devices or electronics.

“We've really just optimized our conventional system by tightening our tolerances,” Larson says. “Our engine's three vortex combustion system [TVCS] obtains optimum air/fuel mixture by generating three intense airflow vortexes within a spherical combustion [swirl] chamber. This ensures that all the fuel gets burned as cleanly as possible.”

According to Larson, further optimizing the TVCS boils down to improving the swirling action so that the Kubota engine never has too much or too little fuel or air in the combustion chamber. “Practically speaking, we've minimized emissions by improving the air/fuel mixture and shortening the ignition delay,” Larson explains. “The new environmental ETVCS engine exceeds all existing standards in the U.S., Europe and California while maintaining top performance and fuel economy.”

Larson admits that Kubota's elegant, relatively gadget-free solution has a potential downside during EPA testing. “The EPA's audit test system randomly picks five engines from the factory and takes the statistical average of their emissions to determine compliance. If just one engine is off spec, we can't just tweak some electronics to fix it,” he says. Because one bad apple truly could ruin the whole barrel, Kubota has to get it right every time off the line, with a production process that's extremely consistent and set to tight tolerances. The upside is that, theoretically, there's much less chance for the Kubota buyer to end up with a lemon.

Valtra low-rev philosophy

In heavy trucks, manufacturers aim for economical fuel consumption by reducing maximum operating speed of the engine. Finland-based Valtra has made the same shift in farm tractors with its EcoPower line. A happy side effect: An engine that burns less fuel will usually produce fewer emissions.

Two years ago, Valtra introduced its low-rev concept in its 135-hp 8350. It has become Valtra's most popular 6-cyl. tractor. Model 6750, released this year, is a 105-hp, 4-cyl. EcoPower tractor. The Valtra idea is to shift down the operating speed range of the tractor by approximately 400 rpm, which reduces parasitic losses in the engine and in the transmission caused by speed. Correspondingly, the tractor transmission and PTO speeds have been adapted for a lower operating speed.

The low-speed engines are based on the already efficient Valtra Sisudiesel, also used in Massey Ferguson tractors. The nominal operating speed of the EcoPower 4-cyl. engine is only 1,800 rpm, about 25% slower than that of conventional engines. The rated power of 105 hp is reached at 1,500 to 1,800 rpm. Fuel consumption is approximately 10% lower than that of a traditionally tuned engine. This immediately cuts the exhaust gases by 10 to 15%. And with slower-moving pistons, less oil seeps around the rings during each hour of use.

“A good-sized bore and long stroke are the key factors that let these engines run at slower speeds,” says Valtra aftermarket specialist Stuart Maxwell. “In that regard, they're a lot like the old Minneapolis tractors of 35 to 40 years ago. What's different is that the Valtra engines are very precisely balanced and use modern supercharging and after-cooling technology too. We also redesigned the pumps to work at these lower speeds.”

The lower engine speed puts less wear on the engine and allows for longer, 500-hr. oil change intervals.

Reducing the operating speed also reduces engine noise, Maxwell says. “You'll be surprised at how low of an operating speed is needed for partial loads in various tasks normal for a tractor of this size,” he says. “It's a lot quieter in the cab, with less vibration, yet the torque is still there. In fact, I'd say you can get as much work out of our 135-hp engine as you could out of a 160-hp conventional engine.”

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From 1988 to 2007, NOx and particulate matter emissions from heavy-duty highway diesel engines will be reduced by 98%. Off-road emissions will follow a similar path.
— Diesel Technology Forum


Diesel powers:

66% of all farm equipment
89% of all agricultural trucks
100% of all railroad, barge and ocean grain transport

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