Between January 1, 2006, and January 1, 2007, a new generation of low-emission Tier 3 diesel engines will begin rolling off assembly lines. There won’t be any surprises as far as the technology and performance of these engines – most of the technology was decided on in 2002. Caterpillar is forging ahead with its ACERT (Advanced Combustion Emissions Reduction Technology) and the rest of the OEMs are producing Exhaust Gas Recirculation (EGR) designs or manipulating fuel injection for more complete combustion.
With low-sulfur fuel coming down the pikes, these technologies will meet the U.S. Environmental Protection Agency’s emissions requirements for off-road engines without modifications or after-treatment devices until Tier 4 comes due in 2011.
Yet even though the engines’ designs are established, a lot of related technology is changing between now and the advent of Tier 4. For example:
- Some regions of the country are setting their own emissions standards, which will require the installation of aftermarket devices on heavy equipment with pre-Tier 3 engines.
- New heavy-duty diesel lube oil standards are being finalized for adoption in late 2006.
- The sulfur content of off-road diesel fuel is going to drop from the current level of around 3,000 parts per million to 500 ppm in 2007 and then 15 ppm in 2011.
After treatment or else
In the past, engine exhaust standards were set as a national standard. Only Southern California (because of its notorious smog), was granted the right to enforce stricter rules than the EPA national standards. But this principle has flown out the window in the past few years and there are now multiple regional jurisdictions that have imposed their own emissions standards in excess of what EPA requires. And it’s not just California. Contractors wanting to bid on any number of government-funded projects throughout the country are being asked to meet stricter emission standards well ahead of the national timeline.
The only way contractors can meet these standards with their current machines is to install aftermarket exhaust after-treatment technology. These devices are readily available, but they’re not cheap, running anywhere from $3,000 to $30,000. And because they’re fairly large components, they’re most often installed outside the machine’s engine cowling or hood. Once you have them installed though, these devices can bring a Tier 0, 1 or 2 engine up to essentially the same particulate matter emissions standards as a Tier 3 engine – so you can still bid on publicly funded jobs in these areas and not have to repower or replace an older machine.
There are two types of exhaust after treatment:
- Diesel oxidation catalysts (DOCs) are flow-through devices that act like a catalytic converter in a car. Exhaust gasses blow past a heated catalyst, which burns contaminants at a relatively low temperature and reduces them to carbon dioxide and water vapor.
- Diesel particulate filters (DPFs) burn exhaust gasses but also trap hard carbon particles in the exhaust stream and then burn them up. The particulate filters look like an oxidation catalyst except every other channel is plugged at one end to create the filtration effect.
DOCs are approximately 20 percent efficient, whereas DPFs are more than 90 percent efficient, says Fred Schmidt, director of sales for emissions at Donaldson. But DPFs, because they’re not flow-through devices, tend to plug up depending on the level of emissions in the exhaust stream. For Tier 0 engines, the emissions are too high for a DPF and DOCs are the best solution. Tier 1 engines, depending on how clean they burn, can sometimes use DPFs, and most Tier 2 engines will do fine with DPFs, Schmidt says.
DOCs can often be installed as direct muffler replacements, Schmidt says, but DPFs are too large. Since most machines today already have crowded engine compartments, the only alternative is to mount the DPF outside the sheet metal someplace where it won’t disrupt the operator’s sight lines.
Installed prices for DOCs run from $3,000 to $4,000, says Schmidt. DPFs vary in price more, anywhere from $4,000 to as much as $30,000 with the cost going up as horsepower increases. And although they’ve not been in use very long with off-road equipment, in the on-highway engines they’re lasting in the range of a half-million miles – about half the life of the engine. Design and installation of an after-treatment device is best left to a filtration specialist, says Schmidt.
Funding and government grants
Knowing that outfitting thousands of machines across the country with DPF or DOCs might put a squeeze on contractors’ cash flow, the federal government passed the Diesel Emission Reduction Act of 2005 in June. The law is intended to appropriate $200 million annually to be paid over five years to contractors who outfit their older machines with aftermarket technology. The law passed both houses of Congress and was signed by President Bush and is now sitting in the Ways and Means Committee for funding approval. But the money is not available yet and some question whether the funds will be frozen given current federal deficits and the Hurricane Katrina cleanup.
In California there is some state-level funding available for retrofits, says Schmidt, but on a case-by-case basis. “Basically you have to find grant money. Several air quality management districts give money each year to different projects. They’re doing it to improve air quality and to gain experience.” But, cautions Schmidt, once California’s diesel emissions regulations become law – and that will likely happen in the next 12 to 18 months – the state funding will stop. “Once there is a regulation, all that will be on the backs of the users,” he says.
Numerous other state programs – the Texas Emissions Reduction Plan, the Carl Moyer Program in California and programs in Maryland, Massachusetts, Ohio, New York and Washington – also help contractors with the costs of exhaust aftertreatment.
New lube oil for a new age
Lube oil manufacturers are hard at work getting ready for a new standard for heavy-duty diesel oils for the next generation of engines. The new standard, for now dubbed Proposed Category 10 or PC-10, will extend the life and/or reduce maintenance on exhaust after treatment devices and resolve a number of issues that came up with the introduction of the Tier 2 engines in 2001/2002. The main beneficiary of PC-10 oils will be on-highway truck engines, which have stricter emissions standards, more EGR usage and more aftertreatment, but off-highway engines will benefit as well.
Just prior to the Tier 2 engines entering the marketplace, the lube oil manufacturers came out with the CI-4 lube oil standard. But some engine manufacturers were still concerned about how the new engines were going to do in the field and many soon issued their own oil specifications, all with subtle differences, to err on the side of caution.
“For PC-10 it looks like they’re all coming closer, but it’s not all ironed out yet,” says Dan Arcy, technical marketing manager for Shell’s heavy-duty motor oils. It is anticipated that in February 2006 the new category specifications will be announced, at which time the category will likely be renamed API CJ-4. Then sometime late in the fall, the various petroleum manufacturers whose oils meet these standards will be granted the license to put the API CJ-4 stamp on their products.
Less Alka-Seltzer, longer after treatment life
The new oils will have significantly less sulfur and phosphorous in them (which becomes ash in the combustion process) to protect the after-treatment devices on retrofitted heavy equipment and most 2007 truck engines.
Today’s API CI-4 oils have a Total Base Number (TBN) of around 11 to 13 and an ash content of 1.2 to 1.5 percent, says Mark Betner, heavy-duty product manager for Citgo. The PC-10 oils, by contrast, will have a TBN of 8 to 10 and ash levels of 0.9 to 1 percent. In previous oil formulas, the ash was used to boost TBN levels, but ash also clogs up exhaust after-treatment devices.
“The higher ash levels won’t cut it when it comes to after-treatment devices on diesel engines,” says Jim Putz, category manager for commercial transportation products at Petro Canada. “You won’t get the same longevity.”
In low-ash oil formulations already in use in Europe, the reduction in deposits on after-treatment devices has been significant, Arcy says. “What it comes down to is a maintenance issue,” he says. “There is a lot of work being done to determine what the cleaning interval is and how those practices will be done.”
The lower TBN, what Betner calls the oil’s “Alka-Seltzer system,” will correspond with the low-sulfur-content fuels in 2007. The sulfur in diesel fuel contributes to acid formation inside the engine and, with less sulfur, engines will have less need for the acid-neutralizing effect of ash.
Some questions still remain as to whether PC-10 oils will have sufficient acid neutralizing capacity for the current crop of Tier 2 EGR engines running on high-sulfur fuel – or whether this could create a two-fuel/two-oil environment. Most experts think not. Backward compatibility is a design target for PC-10 oils, Putz says. But it may be the case that drain intervals will be shortened for Tier 2 engines running high-sulfur fuel with the new oil formulations.
Higher quality base stocks
Another feature of the PC-10 oils is that they will be using a higher quality base stock. (Lube oil is primarily base stock with detergents and additives blended in to achieve certain performance characteristics.)
“We’re going to need the higher quality base stocks to handle the extreme levels of soot and the higher temperatures,” Putz says. “We’re going to see EGR rates going from 13 percent to 30 percent, and as high as 70 percent with engines idling,” (EGR rate is the percent of exhaust gas that is recirculated into the combustion chamber.) “So what you need is an engine oil that can disperse soot better than anything before, better than a CI-4 Plus oil.” The higher quality base stocks will also better resist breakdown under heat, what the industry calls oxidation stability.
Better base stocks also hold out the possibility of better drain intervals. “Drain intervals aren’t set in stone for the 2007 engines, Arcy says. The low-sulfur fuel and better oxidation stability of the lube oils favor longer drain intervals. Higher heat and EGR work against longer drain intervals. “Shell has a lot of field testing going on to determine what the drain intervals will be,” he says.
Tier-3 off-road engine technology
Caterpillar’s ACERT technology uses a fuel system that puts multiple fuel injections and different combinations of injections into the cylinder for each combustion cycle and an advanced air system that provides the needed air for different loads and speeds. There are more than 10 million possible combustion combinations monitored by a software-driven electronic control module that precisely and completely burns the fuel in the cylinders. Perkins 1104 D series also use elements of ACERT along with mechanical fuel management with no changes to hookups or footprint so installations are not affected.
Cummins used “analysis-led design” to model the combustion process. This allowed the company to create in-cylinder combustion technology that optimizes fuel and air parameters to reduce emissions without the need for EGR, aftertreatment or variable geometry turbochargers, thus minimizing the installation impact. QSC and QSL platforms keep the same engine envelope and the QSB is almost the same except that the rear gear train increased in length slightly. All three get common rail fuel systems.
Detroit Diesel Series 60 Tier 3 off-highway engines keep the same cylinder heads and modified intake ports as developed for the Tier 2 engines and added a camshaft with a modified exhaust lobe, new piston bowl shape and electronic control units. The Series 900 engines feature exhaust turbocharging, charge-air cooling, high pressure injection systems with solenoid controlled unit injection pumps and electronic engine management.
John Deere Power Systems has three engine designs in its Tier 3 lineup. The PowerTech Plus models use cooled EGR with a variable geometry turbocharger and four-valve cylinder heads. An electronic engine control unit controls the fuel system, air-to-fuel ratio, VGT output, and cooled exhaust gas and fresh air mixing for peak performance and fuel economy. The PowerTech E engines have two valves per cylinder; high-pressure, common-rail fuel systems (4.5 and 6.8 liter); air-to-air inter-cooling and electronic unit pump fuel systems (on 2.4- and 3.0-liter models) and turbocharged or air-to-air inter-cooling. PowerTech M engines meet their Tier 3 obligations with a new mechanical fuel system, two valves per cylinder and standard or wastegate turbochargers.
Komatsu’s Tier 3 compliant engines have a new electronic control system to maximize performance across a wide range of conditions. Its heavy-duty, high-pressure common rail fuel system optimizes control of multiple injection volumes, and a cooled EGR system eliminates most emissions from the exhaust stream. A new computer-modeled combustion chamber ensures a more complete burn and an air-to-air charge cooling system feeds the cylinders sufficient volumes of air to reduce emissions and benefit fuel consumption.
Volvo’s Advanced Combustion Technology (V-ACT) was developed for the company’s 9- to 16-liter engines and includes new flexible fuel injection systems with high-pressure capability, fixed geometry turbochargers for improved flow, switchable internal exhaust gas recirculation systems, new radiators and enhanced engine ECUs. Volvo medium-duty engines will meet Tier 3 standards with similar technology.
