It's relatively easy to spot equipment designed to meet ever-tightening emission standards. Exhaust Gas Recirculation (EGR) systems are bolted on the side of the engine blocks, cooling systems are larger than ever, and if you come across an exampl...
It’s relatively easy to spot equipment designed to meet ever-tightening emission standards. Exhaust Gas Recirculation (EGR) systems are bolted on the side of the engine blocks, cooling systems are larger than ever, and if you come across an example from a test fleet built to meet 2007 standards, you’ll probably notice the addition of a particulate trap – along with exhaust stacks that are gleaming thanks to lower levels of soot.
Look just a few years down the road, to 2010, and exhaust will be at least as clean as the air that’s drawn into the engine, offers Steve Charlton, executive director of Cummins’ Advanced Engineering Group. “[But] there will be plenty of work to do between now and then.”
Despite the technical challenges, however, much of the work has already been completed to prepare for the US Environmental Protection Agency’s 2007 requirements. Manufacturers suggested during a recent Technology and Maintenance Council meeting in Toronto that engine designs will look remarkably similar to existing models — right down to the promise of similar oil drain intervals and fuel economy — thanks in part to such things as a coming category of engine oils and ultra-low sulfur diesel (ULSD).
Fuel-efficiency will be one of the key factors as the manufacturers compete with each other, Charlton says. “Meeting emissions is kind of important, but it’s really just a ticket to the dance. We know we’ve got to do it.”
Most manufacturers expect to trim allowable NOx levels down to 1.1 g/bhp-hr from current levels of 2.5 g/bhp-hr by accelerating the rate of EGR. Cummins, for example, will begin to recycle 25% of exhaust gases compared to current levels of 15%. Caterpillar, meanwhile, will refine the combustion process of its ACERT engines to meet the same goal.
Granted, there will be other changes to the engine block. Tim Tindall of Detroit Diesel points to plans for his company’s Series 60 designs that include a larger EGR cooler, a different variable geometry turbocharger design, and updated electronic controls. The EGR valve will also move to the intake side of the engine, and a new system will capture gases that traditionally escape from crank cases.
They’ll also be available only in 14-litre displacements.
Perhaps the most significant change involving 2007 designs will be the introduction of particulate filters to screen the microscopic contaminants that would otherwise flow from exhaust stacks. The new rules limit emissions of particulate matter to .01 g/bhp-hr compared to existing levels of .1 g/bhp-hr.
The filters are expected to replace traditional mufflers on exhaust systems, and present some of the biggest engineering challenges associated with the pending rules.
In the best-case scenarios, they will be mounted near engines because of their need for high exhaust temperatures. That will place them on the frame rail just inside the fuel tank on most highway tractors. But they’ll have to be mounted vertically behind day cabs and medium-duty trucks because of limited space, and those mounts have damaged ceramic filtration material in early prototypes, Tindall says.
The systems will also need to be fed with a supply of fuel that can be used to oxidize soot when exhaust temperatures aren’t high enough to do the job, such as when the truck is running under a light load.
“It’s not a flamethrower,” Charlton says of the “regeneration” process. “It’s simply a slow, low-temperature oxidation. This has nothing to do with having flames or burners in the exhaust.”
That active process will take about 10 minutes, and will typically occur every four to 16 hours of a truck’s operation, says Steve Berry, director of government relations with Volvo Powertrain.
“The big challenge we face with the active regeneration is when to do it, where to do it and how to do it,” Tindall says of the role that the engine controller will play in the process. And since exhaust outlet temperatures will reach 650 to 670 Celsius when that happens, “it’s got to be done carefully to prevent damage to the filters,” he says. “You can only allow filters to get so warm before they themselves oxidize.”
There may also be ways to refine the combustion process to limit the amount of soot that goes in the filter in the first place, adds Mike Powers, Caterpillar’s product development manager.
Still, the filters will have to be cleaned of the ash generated from engine oils, and their replacement is expected to be relatively straightforward – involving the loosening of a couple of clamps to remove the entire unit.
The filters will have to last about 240,000 kilometres or 4,500 hours before needing to be replaced. But Charlton suggests most will last well over 320,000 km.
“Expect to be able to exchange the (Diesel Particulate Filter) within the time of an oil change,” Berry says, adding that a typical service will cost about $150.
But don’t expect to be able to use filters across multiple truck models. “They’ll be engine-specific,” Tindall says. “Even within an engine, there can be different sizes of filters, depending on horsepower output.”
It’s like a turbocharger, he says. “I don’t think you can take a turbocharger … from one engine to another.”
Meanwhile, engine fluids from oil to fuel are being refined to meet the needs of the new designs. Sulfur levels in diesel fuel need to drop to 15 ppm by 2007, to reduce the acids created in the combustion process, while low-ash engine oils (known as PC-10) will be introduced in the third quarter of 2006 to help extend the life of the particulate traps.
After all, fluids have been a particular focus of maintenance shops dealing with engines built to meet the latest emission standards.
Coolants already need to absorb 30% more heat than their predecessors, thanks to the introduction of EGR, says Darrell Hicks of the Penray Company. But it’s been hard to tell exactly how coolants are holding up, since the cooling systems have been littered with problems, and usually need to be drained during repairs long before the coolant is allowed to wear out.
“We’ve seen campaigns, campaigns, campaigns,” Hicks says of recalls that have affected everything from coolers to valves and turbochargers. “It’s hard to get more than 120,000 to 150,000 miles (190,000 to 240,000 km) on a coolant.”
One thing that is certain is that the use of EGR is rapidly dropping coolant pH levels, while the related heats are oxidizing nitrites faster than ever, leading to the black deposits also known as “yuck” or “bottoms”.
“It’s very hard to get a field test to run to completion,” adds John Martin of Lubrizol, which designs oil additives.
At wide-open throttle, EGR systems add 25% to 35% more heat to the engines. “[And] it causes more wear than abrasive wear,” he says of the related oxidation. “The oil is going to degrade faster. The detergent is going to deplete faster.
“If you got engines later than ’99, you need to worry about soot … watch out for anything with retarded timing.”
Oils in newer engines also need to be watched for high acid levels, shown in an oil analysis as a depletion of the Total Base Number, while blotter spot testing will help monitor dispersency and oxidation.
If the Total Acid Number reaches as high as the Total Base Number, it’s time to change the oil, he says. Conservative? Perhaps. But it may save your engine.
While the 2007 engine designs will be more expensive than their existing counterparts, the price increase isn’t expected to be “of the same magnitude” as the one experienced with the introduction of the industry’s first EGR models, says Volvo’s Berry.
But you can expect some higher prices. The higher heats will require larger cooling systems, Tindall says. (Although, he doesn’t expect any “visual” changes to hood designs to make room for the larger packages.) Diagnostic systems, meanwhile, will have to be introduced in 2010 to monitor fuel injected into the particulate traps, watch over EGR, and monitor excessive backpressure that can indicate a clogged filter, or inadequate backpressure, which can suggest it’s missing or failed altogether.
Higher injection pressures may also require stronger base engine components, Berry adds.
That may not be the end of the higher costs, either. The new fuel generates 1% to 2% less heat than higher-sulfur formulas, Charlton says, and there may be some changes to oil drain intervals as well.
For now, engine makers track their pending deadlines in terms of seasons.
“We’ve got one summer and two winters to go before we have to start producing these  engines,” Tindall says. They’re all focused on the requirements for seasonal testing before new designs are unveiled to the industry as a whole.
Unlike 2002, when a U.S. Environmental Protection Agency ruling forced everyone to accelerate plans to introduce EGR, the manufacturers suggest they’re ready.
“We’re in a far different situation this time around,” he says. “We can meet the emission standards of 2007. We know how to do it.”