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NOX FACTOR: 2007 ENGINES

Posted: August 1, 2014 by Rolf Lockwood

Pollution and politics go together like pork and beans, especially in Washington, D.C. Controversy has surrounded the U.S. Environmental Protection Agency since its birth in 1970 and its first victory, to ban lead in gasoline and require catalytic converters in cars. It’s been winning on the diesel front, too, but the tough emissions standards it has mandated to take effect in 2007 are still the source of second-guessing. And then there’s 2010.

The coming EPA standards–mirrored here in Canada–really are tough. In 2007, half of all on-highway diesels sold will be allowed to emit no more than 0.20 g/hp-hr (grams per horsepower-hour) of nitrogen oxide (NOx), which is a whopping 90-per-cent drop from 2002-04 levels. By 2010, 100 percent of on-highway engines must be at the 0.20 mark.

On top of those reductions, ’07 particulate emissions can’t exceed 0.01 g/hp-hr, also a stunning 90-per-cent drop, a standard that will remain in place for 2010. The challenge is enormous.

And what will you see in January 2007? All engines except the Mercedes-Benz diesels found in some Freightliner, Sterling, and Western Star trucks will follow the basic technology paths that met the 2004 standards. Cummins, Detroit Diesel, Mack, and Volvo will continue with cooled-exhaust-gas recirculation (EGR), while Caterpillar will continue using its ACERT technology. All will add a diesel particulate filter, including Cat, which is already using an oxidation catalyst behind its engines. Mercedes engines will use both EGR and a particulate filter. Engines from all makers will be available in mid-2005 for selected fleet testing.

None of them will use selective catalytic reduction (SCR) technology, much to the chagrin of some major fleets.

All of these 2007 engines will be running on ultra-low-sulphur diesel fuel (ULSD), which the EPA has mandated for mid-2006. It’s a radical reduction of the sulphur content in fuel from 500 to just 15 parts per million. Because it will require different and additional refining methods, transportation means, and storage facilities, it will cost more, though how much more remains to be seen. U.S. estimates suggest up to five cents per gallon. Older diesels will run fine on the new fuel.

And yet again, ’07 diesels will require another new lube-oil spec just as present models did. That much we know, more or less, but the fighting really doesn’t seem to be over. Even the General Accounting Office, the non-partisan investigative arm of the U.S. Congress, called for an independent examination of the ’07 rules in a report issued in mid-March (see www.gao.gov).

“We think there are sufficient technological challenges to justify a second independent review panel,” said John Stephenson of the GAO in a presentation to delegates at the annual meeting of the Technology & Maintenance Council in Fort Lauderdale, Fla., on March 16. Taking part in a full day of panel sessions, called the Diesel Engines Emissions Summit II (another was held last fall), he said several technological issues were missed in a previous review. Among them, he said, is the distribution of ULSD fuel. He wants incentives on the table for fleets, in hopes that such action might prevent the massive pre-buy of trucks with old-style engines that occurred in advance of October 2002 when the ’04 standards went into effect. He’s not, by a long shot, alone in that wish, nor in thinking the pre-buy in two years’ time could well be even bigger.

In his remarks to the Summit, American Trucking Associations president and CEO Bill Graves took a similar position. “We think there should be a cost/benefit analysis done on the impacts of the ’02 rules with regard to fuel economy,” he said. The trucking industry is ready to do more in environmental terms, governed by common sense, Graves added. The ATA is also looking for tax credits to encourage truck buyers to accept ’07 engines.

The GAO’s Stephenson was book-ended at the lively first session of the TMC summit by Jeff Holmstead, assistant EPA administrator, and populist Republican Congressman Mac Collins from Georgia, himself a truck fleet owner.

Holmstead was conciliatory. “This ’07 rule is a big deal. We know that,” he said. “We are absolutely committed to making this work.”

Collins wasn’t buying it. Critical of the EPA and its handling of the 2002/04 emissions rules, he said the consumer’s pocketbook must be considered in the course of protecting the environment. He said we don’t know enough about the economic impact of the pull-forward of 2004 rules to October 2002, and he guessed that it was much more than anyone imagines.

“The truth of the matter is that I don’t trust the EPA, and I caution you to be careful,” he told the 1,100 Summit delegates in closing. “We should never have a government that we can’t trust.”

Some time next year engines meeting the 2007 emissions standards will be on the road in real-world tests, operated by fleets in revenue service. All diesel makers say they’ll meet this goal, and oil refiners say they can supply enough ULSD fuel to facilitate the testing. They’ll stablish “corridors,” routes along which the fuel will be available in advance of 2006.

The test engines will be pre-production models, giving the industry a chance to work out the inevitable bugs over the course of 18 months or so. That will be a welcome change from October of 2002, when engine makers and fleets alike complained of too little development and testing time.

Here’s what you can expect:

Caterpillar’s ACERT solution, which presently employs a mix of injection, combustion, and electronic tools along with exhaust aftertreatment, will continue on that path. Cat’s John Campbell told Summit delegates that the 2007 ACERT engine will employ a “next generation” fuel system, advanced combustion technology, better thermal management, and a particulate filter.

Cat’s aiming at a 150,000-mile interval for filter maintenance. Issues revolve mainly around fitting the filter in a chassis while maintaining serviceability. There may also be a secondary filter required, he said. The company doesn’t have a final design for the closed crankcase ventilation system that all ’07 diesels will require, by EPA decree.

At Cummins, said Dr. Steve Charlton, ’07 engines will look exactly like their ’02 brethren, though they’ll need an active particulate filter. A “passive” filter takes advantage of normal exhaust heat to “regenerate” itself periodically, meaning it oxidizes accumulated soot and cleans itself with the help of a catalyst. An “active” filter creates additional heat when needed by electric means or by an injection of fuel, managed by engine software. Passive filters are generally ineffective at low loads and low ambient temperatures.

PM filter technology has been under development at Cummins since the 1980s. The company is working with lube-oil additive suppliers to come up with low-ash compounds with the target of maintenance-free filters by the time we get to 2007.

Charlton corrected statements made by some others, saying that a particulate filter will not be irreparably harmed if fed high-sulphur fuel. It will get dirty faster, and the truck will probably not meet emissions standards for a time, but the filter will eventually clean itself out.

Cummins is now working on packaging and integration issues with truck makers. It has prototype engines running in trucks today and will have 20 to 30 development engines in customers’ hands by mid-2005.

Detroit Diesel’s Tim Tindall said the company is still running parallel development programs with both EGR and SCR technologies, having chosen the former for North America, the latter for Europe. Developments of the ’02 Series 60 technology now in use include changes to the fuel system and to the troublesome EGR valve, advanced electronics, additional sensors, and a closed crankcase ventilation system as well as an active particulate filter.

The filter’s design is not finalized, Tindall said. Engineers are still working on its regeneration method and its physical shape. He added that heat rejection remains an issue, saying an ’07 engine may run a little hotter and could conceivably require a larger radiator.

Tindall sounded a cautious note in closing, saying that 2007 levels can be achieved, but the cost will be high.

A new heavy-duty engine being developed by DDC and parent company DaimlerChrysler, scheduled for release in 2007, will also employ EGR and diesel particulate filters for North American applications.

At Mack and Volvo, a common engine (based on the present Volvo 12-litre model, though a larger block may be coming) will find its way into both chassis brands, marking the end of the Mack E7, and will feature cooled EGR with active particulate filtration.

Volvo’s Tony Greszler told the packed TMC auditorium that the company’s target is to offer a filter that needs no service until 300,000 miles, double what others were estimating. That service cost should be about $50, he said. He anticipates no reduction in other service intervals, and said they might even be extended. The company plans to have about 30 engines in field testing with selected customers in the spring of 2005. Having also developed SCR engines for Euro 4 (and until recently it was thought Volvo would use them here too), Volvo says that technology remains promising for applications in North America.

Clearly, the key to the success–and much of the extra cost–of all 2007 engines will be the particulate filters they employ. It’s also clear that passive filters won’t be up to the job universally, that active types will be required in many or even most applications. Steve Duley of Schneider National says he’s concerned about the cost of these particulate filters, saying they look simple but aren’t likely to be as simple to own.

They will add weight, about 80 to 100 pounds, says Pedro Ferro, vice president and general manager of ArvinMeritor’s Commercial Vehicle Exhaust division. His company, better known for axles and brakes and such, is in fact a leader in the exhaust filtration field, including SCR, and its Thermal Regenerator is an active particulate filter that boasts 99% filtration efficiency without using expensive precious metals on the filter media. The system identifies when regeneration is required, then injects a small amount of fuel into the exhaust stream to reach soot-burning temperature in seconds. The regeneration takes about 10 minutes and would typically be required every 100 hours, consuming a half-litre of diesel fuel.

Ferro looks ahead to 2010 and, as most engine makers are speculating, sees the need for additional hardware to control NOx in the exhaust stream. SCR can achieve that, as can so-called NOx adsorbers, but EGR probably can’t do it on its own.

But the more immediate questions concern 2007 and especially the likelihood of another round of pre-buying. There’s no doubt that ’07 engines will be more expensive, though cost estimates are impossible to come by.

One maintenance manager we talked to at TMC, with a sizeable western Canadian fleet (he wants to remain nameless), said he has yet to buy an ’02 engine and wishes he could continue rebuilding his older diesels ad infinitum.

As strategies go, that may not be altogether practical. But we’ve heard worse.

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