Just before a set of more stringent emissions standards for diesel truck engines took effect, a friend deliberately bought a shiny new truck with a dirty old-style engine—one of the last of its kind to roll off the assembly line.
If you’re considering such a perverse strategy to update or expand your fleet of backhoes, bulldozers, cranes, excavators, graders, and other construction equipment as effective dates for lower nonroad diesel vehicle emissions approach, think twice. Buying the best available technology may cost a little more, but not doing so has other adverse effects.
The process by which nonroad diesel engines will become progressively cleaner over the next decade is a classic example of “technology forcing.” Regulators have imposed a set of requirements for cutting emissions. Now engineers are figuring out how to meet the requirements. As they succeed, you’ll be both pushed and pulled to adopt the new technology.
The push comes from the EPA, which has set four “tiers” of emissions standards governing nonroad diesel engines. Each tier allows for a phase-in period of several years based on engine size (see tables in the sidebar).
Tier 1 standards, phased in from 1996 to 2000, set the first limits on emissions of carbon monoxide, non-methane hydrocarbons, oxides of nitrogen, and particulate matter.
For Tier 2’s more stringent standards, the phase-in period began in 2001 and will conclude in 2006.
For Tier 3, with standards still more stringent for engines from 37 kilowatts (50 horsepower) to 560 kilowatts (750 horsepower), the phase-in period will extend from 2006 to 2008.
Tier 4, with a phase-in period extending from 2008 to 2015, entails a 90% reduction in oxides of nitrogen and particulates from the Tier 3 level—a major challenge for engine manufacturers. Their research will yield solutions almost as diverse as those the automotive world experienced early in the 20th century, when diesel, electric, and steam propulsion systems vied for dominance with those powered by gasoline.
Because meeting the Tier 4 diesel-engine standards likely will require catalytic aftertreatment technologies that sulfur can contaminate, Tier 4 also mandates major reductions in the sulfur content of nonroad diesel fuels and lubricants beginning in 2007.
Marketplace Pull
While the EPA pushes you into compliance with these new standards, the marketplace will pull you in the same direction.
The EPA’s standards apply only to engines that are new as of the effective date for each tier and engine size, but on many jobs you may not be able to use older equipment.
Look for growing numbers of your clients to make compliance with current standards a condition of bid. Indeed, even your newest equipment that meets current EPA standards may not suffice if a client requires you to achieve a higher tier of reductions several years in advance of the EPA deadline.
Catalytic Exhaust Products Ltd. in Brampton, ON, Canada, makes a variety of emissions control devices for diesel engines. “Our customers have to look at the environmental requirements of the contracts they’re trying to win,” says John Stekar, the firm’s chief executive officer. “Some contracts specify emission limits. Some stipulate the use of control devices. Some stipulate the type of control equipment that can be used. Some specify the fuel and the control devices.”
New York City’s policy is a byproduct of the September 11, 2001, terrorist attacks on the World Trade Center. With so much construction equipment concentrated at Ground Zero, city officials and contractors collaborated to track and reduce emissions. Then the city applied the emissions reductions thus achieved to its ongoing public works program.
“If you wish to do a job for New York City, you have to retrofit your equipment to meet their lower emission regulations,” notes Cameron Larson, senior engineer for emissions standards at Kubota Engine America Corp. in Lincolnshire, IL. “They have their own purchasing authority and have the right to say, ‘We will only let people bid who meet these lower emission regulations. If you wish to bid on this job, you may need to bid higher if it costs you more to meet the regulations, but so will everybody else.’”
Replace or Rebuild?
“Equipment owners who wish to have emissions benefits should seriously consider scrapping or trading in their aging equipment,” advises John Madey, product manager at Iveco Motors North America in Carol Stream, IL. “New equipment will be more efficient and cost less to operate. This will force old equipment to work its way out of the marketplace via attrition and obsolescence.”
If you can’t afford to buy new equipment, several options exist to bring your old equipment into compliance. One is engine replacement. Some manufacturers offer new replacement engines, which are easy to install if the manufacturer followed the original engine’s mounting specifications. Otherwise, the new engine may not fit into the old one’s space without costly mounting modifications.
New replacement engines must meet the standards in force when they are built. “The rules are written to favor replacing an unregulated engine with the latest emissions-regulated engine,” Larson says. “That can be more economical than buying a new bulldozer, if the rest of it is still hanging in there.”
Other benefits of installing a new engine include noise reduction, more horsepower and torque, an improved fuel system, and “many durability enhancements,” says Bruce Farrar, manager of off-highway communications for Cummins Inc. in Columbus, IN.
Another alternative is a remanufactured engine, which the EPA says must be rebuilt “to its originally certified configuration for all the relevant tolerances, calibrations, and specifications that might affect emissions.”
In most instances, Farrar says, upgrading a prior-tier engine to the latest emissions standards is less cost-effective than installing a new engine. Moreover, even if a remanufactured engine meets EPA requirements for a previous tier of emissions control, it may not satisfy an individual client’s tougher bidding requirements without an additional aftertreatment system.
Aftertreatment Options
Choosing the right aftertreatment option for a diesel engine depends on the equipment you’re trying to retrofit, the emissions it produces, and your clients’ requirements. Possibilities include the following:
- A catalytic converter with a diesel oxidation catalyst (DOC). A ceramic or metal monolith coated with a precious metal, a DOC oxidizes pollutants to produce carbon dioxide and water. Stekar says a DOC can remove from the exhaust stream more than 90% of carbon monoxide, 70% to 85% of hydrocarbons, and 20% to 40% of particulate matter.
- A selective catalytic reduction (SCR) system. Designed to combat oxides of nitrogen, SCR adds aqueous urea to the exhaust stream, which then passes through a catalytic converter where the catalyst removes up to 90% of oxides of nitrogen from the exhaust.
- Diesel particulate filters (DPFs). Made of ceramic materials, silicon carbide, or high-temperature paper, DPFs have porous walls with holes measured in microns that trap particles larger than the holes. Some are strictly mechanical and must be replaced frequently. Others have catalysts that oxidize trapped particulates. The catalyst may be applied to the filter, or added to the fuel. “We’re also working on an electrically regenerated DPF that uses electrical energy to increase the heat, thereby burning the filter clean,” Stekar says. Mechanical DPFs remove only particulates; catalytic DPFs can remove from the exhaust stream 85% of particulate matter and over 90% of carbon monoxide and hydrocarbons.
- Engine heating equipment. A niche product in the nonroad mobile arena, engine heaters have been used primarily in extreme cold where an engine shut off overnight may be difficult or impossible to restart the next morning. Now, in more moderate climates, engine heaters are beginning to attract interest for pollution control purposes.
An engine heater employs a resistance heating element to preheat the lubricating oil and engine coolant. A heated engine eliminates overnight idling and the noxious white smoke that accompanies cold starts. “The engine starts fast and produces drastically fewer emissions,” says Michael Floyd, marketing communications manager at Kim Hotstart Manufacturing Co. Inc. in Spokane, WA.
“Preheating also reduces overall wear and tear on an engine because it requires much less idling time. Regardless of engine size or ambient temperature, 90% of engine wear is due to low water jacket temperature. So when any engine is started without pre-heating, that is when the most damage occurs.”
Retrofitting an aftertreatment device onto an elderly engine can help reduce emissions, though perhaps not enough for the requirements you’re trying to meet. “Control devices have limitations,” Stekar says. “It’s the old analogy of trying to stop the blood from coming out of a head wound.”
Advanced Technologies
Although the EPA standards provide common goals for emissions reduction, individual diesel-engine manufacturers are pursuing those goals in different ways, mixing and matching a smorgasbord of technological options—microprocessor-based electronic engine controls and fuel-injection systems, combustion-chamber geometry that maximizes swirl and turbulence, turbochargers, and exhaust-gas recirculation (EGR).
Some companies won’t discuss what they’re doing; others proudly trumpet their progress. In the latter category:
In 2004, Peoria, IL–based Caterpillar Inc. became the first manufacturer to meet the Tier 3 standards for nonroad vehicles with a full line of seven engine models. Caterpillar’s approach, called ACERT (Advanced Combustion Emissions Reduction Technology), involves air- and fuel-management systems and advanced electronics. To meet the Tier 4 standards, Caterpillar says it may add a DOC. ACERT uses turbochargers to force cool, clean air into the combustion chamber while the fuel system injects small, multiple shots of fuel at appropriate times. An electronic control module integrates the engine’s operation as well as hydraulics, the transmission, and other systems and components to optimize emissions, fuel economy, and performance. Cummins believes “the right technology [for nonroad mobile engines] is an in-cylinder solution,” according to Farrar. “For nonroad applications, cooled EGR is not the path to take,” he declares. With cooled EGR, a valve recirculates a measured amount of cooled exhaust gas back into the intake manifold to mix with incoming fresh air. This removes some oxygen from the engine’s air supply, reducing the peak combustion temperature. Farrar says cooled EGR’s disadvantages for the nonroad user include more frequent oil changes, and the need for larger fans and radiators that cause “parasitic power loss.” Internal (uncooled) EGR reduces oxygen concentration in the combustion chamber by recirculating hot exhaust gas directly into the combustion chamber, but because it’s hot, the benefits of internal EGR are limited. “The air/fuel ratios are also reduced, resulting in increased smoke and fuel consumption,” Farrar says. John Deere Power Systems of Waterloo, IA, has focused on the need to reduce oxides of nitrogen without increasing particulate matter. Deere and other manufacturers face a Hobson’s choice—the temperature-based inverse relationship between oxides of nitrogen and particulates. With a higher engine-cylinder temperature, combustion yields less particulate matter but more oxides of nitrogen. With a lower engine-cylinder temperature, combustion yields more particulate matter but less oxides of nitrogen. Adding to the complexity, particulate-removal devices can increase oxides of nitrogen by causing an afterburning reaction in the exhaust stream. To optimize control of oxides of nitrogen and particulate matter, Deere is using cooled EGR and a variable-geometry turbocharger. The turbocharger helps drive EGR, measuring the amount of exhaust gas that recirculates into the fresh-air stream. Variable-pitch vanes in the turbocharger adjust based on load and speed. An electronic control unit regulates the amount of EGR, the pitch of the turbocharger vanes, the air-to-fuel ratio, and the timing of multiple fuel injections.“The end product is much better than in the past, and a lot more complex,” he says. “What matters is people’s perception of the complexity. On the gasoline engine, the result was credible improvements in economy, power, and reliability. We have the same potential for improving diesel engines.”
Looking Toward the Future
Instead of tweaking current diesel technology to meet the EPA standards, some researchers are developing new diesel-fueled engines as radically different from present models as the latter are from Rudolf Diesel’s original engine patented in 1892.
One avenue of exploration is materials that retain their strength at high temperatures, allowing an increase in combustion temperature to make an engine more efficient. An example is Inconel, a family of nickel-chromium-iron alloys. Some of these “super stainless steel” products contain molybdenum and columbium or niobium to stiffen and strengthen the nickel-chromium matrix without a special hardening treatment.
Also being studied is electronically controlled camless technology. In an engine without camshafts, the crankshaft controls the position of the pistons to discharge exhaust before admitting a fresh charge of air and fuel. Electronics regulate the timing and composition of each charge. In one camless approach, variable valve timing, valve operation relies entirely on solenoids that open and close valves electronically, allowing adjustment of the engine timing to optimize engine performance based on different speeds and loads.
FEV Engine Technology Inc. of Auburn Hills, MI, is working on a camless engine for military applications with funding from the Defense Advanced Research Projects Agency. FEV’s opposed-piston, opposed-cylinder (OPOC) two-stroke diesel engine lacks not only camshafts but also valves, the cylinder head, and all related drive systems.
OPOC differs from the more common four-stroke engine by having only two linear movements of the piston per cycle instead of four. The crankshaft resides between the two cylinders, each of which has two pistons moving in opposite directions. Intake and exhaust ports are at opposite ends of the cylinders. A turbocharger, driven by exhaust gases with an electrical boost, regulates pressure in the cylinders independent of the engine’s operation. This helps maintain a constant fuel-to-air ratio and boosts exhaust-gas recycling, thus reducing oxides of nitrogen emissions.Costs of Compliance
The EPA estimates that the costs of meeting the nonroad diesel emissions standards will add 1% to 3% for most categories of equipment. For example, the EPA says, a typical 175-horsepower bulldozer that costs about $240,000 will need modifications adding about $2,600 (1.083%) to the purchase price.
Industry sources are less precise, but all expect costs to increase. Madey at Iveco Motors says the costs of meeting Tier 3 standards are “a few percent—in the single digits—but Tier 4 is another ballgame, still evolving.”
Some of the Tier 4 technologies now being tested won’t survive, Madey predicts. He foresees a shakeout by 2011 after serious field testing has occurred. “It will be up to the engine manufacturers to educate customers about the pros of their system; everybody else will educate them about the cons,” he says.
Which Tier 4 systems ultimately dominate will depend in part on the cost of fuel, Madey says. “Some systems are better than others in maintaining fuel economy,” he notes. “If fuel prices continue to climb, the emission technologies that reduce fuel economy will fall out of favor, and those that cause fuel economy to remain the same or increase will prevail. If fuel goes cheap again, whatever is cheapest to implement will win.”
Farrar at Cummins notes that cost-effective emissions control solutions for Class 8 on-highway trucks, of which tens or hundreds of thousands are sold each year, “won’t be as easily done or as cost-effective when you talk about the variety of off-highway equipment that any manufacturer would make [and] the harsh working environments in which nonroad equipment is used.”
From the perspective of an engine-parts manufacturer, “The original-equipment manufacturers [OEMs] are using metals and processes that add costs to the component parts. There is no way to avoid this because of the operating temperatures increasing to help meet the emissions standards,” says Russ Nardi, FP Diesel product planner at Federal Mogul Corp. in Southfield, MI. Federal Mogul supplies parts to the OEMs; its FP Diesel Engine Parts division sells to the aftermarket.
Nardi is concerned that the EPA and California Air Resources Board will force diesel engine rebuilders to use only replacement parts from OEMs when repairing or rebuilding an emissions-certified engine. “This would severely limit the customer’s options for cost savings and limit the locations available for repair,” he says. “This would also create a monopoly for the OEMs, effectively putting the aftermarket engine-parts makers out of business.”
Aftertreatment costs will depend upon what technology is chosen or required, says Stekar at Catalytic Exhaust Products. “A diesel particulate filter costs up to 10 times more than a diesel oxidation catalyst, depending on the filter media, the amount of catalyst on the filter, et cetera. For a 100-horsepower diesel engine, a retrofitted DOC device costs about $1,000 at retail, while a typical DPF for the same engine will run between $4,000 and $8,000.”
Engine heaters are relatively inexpensive, costing $20 to $50 for a small direct-immersion block heater, and $200 to $600 for heaters at the top of Kim Hotstart’s product line, Floyd says.
On top of technology costs, users of the next generations of nonroad equipment will face increased maintenance and recordkeeping costs. Staying within the emissions standards requires oil changes, fuel-injector repairs, cleaning filters, keeping critical belts tightened and sensors operational, and keeping records of what was done, so you’ll be ready for a pollution audit.
The Bottom Line
If all of the technology changes and costs associated with cleaning up nonroad mobile diesel-engine emissions seem onerous, consider the alternative. The EPA projects that by 2030, Tier 4’s 90% reduction in oxides of nitrogen and particulate matter from nonroad diesel engines will annually prevent 12,000 premature deaths, 8,900 hospitalizations, 1 million work days lost, 15,000 heart attacks, 6,000 children’s asthma-related emergency room visits, 280,000 cases of respiratory problems in children, and 5.8 million days of restricted adult activity due to respiratory symptoms.
In dollar terms, the health care cost savings of Tier 4 are estimated at $80 billion a year, while meeting the engine and fuel standards will cost just $2 billion a year. Thus, the cost-benefit ratio for the program will be 40 to 1.
Larson at Kubota believes the emissions control effort will work and won’t diminish the dominant role that diesel engines now play in powering nonroad mobile equipment. “I’m an optimistic engineer,” he says. “The problems are going to be solved, and the values inherent in a diesel engine will be there after all these emissions regulations go into effect.”
