������ý

By Frederick Kiel, Staff Reporter

This story appears in the Feb. 9 print edition of Transport Topics.

Starting in 2010, fleets buying new trucks will have to decide between two very different engine systems, and manufacturers already are warning that selecting the competing platform will leave the owner with an inferior product.

All engine makers, except for Navistar Inc., will meet stricter federal emission standards by using selective catalytic reduction, a system already in use in Europe and Japan.

SCR requires diesel exhaust fluid, a mixture of urea and water that is carried in a separate tank and mixed with the truck’s exhaust to cut nitrogen oxide output.

“SCR can be described as modern elegance in chemistry,” David McKenna, director of powertrain sales and marketing for Mack Trucks Inc., told Transport Topics.

Navistar, which makes International Trucks and started production of its MaxxForce Class 8 engine in late 2008, will be the only manufacturer to offer what it calls “enhanced” exhaust gas recirculation, an update of technology that trucks have used since 2002 to meet Environmental Protection Agency mandates.

EGR reduces NOx by recirculating a portion of an engine’s exhaust gas back to the engine cylinders to be burned again.

“Navistar has been building EGR engines since 2004 and we have been perfecting the technology all the time,” said Timothy Shick, director of marketing for the company’s engine group.

Navistar said that, unlike the competitors, its 2010 engines will not require added systems. But SCR proponents said their system already has been proved overseas and will increase fuel efficiency 3% to 5% over current engines, mostly by reducing the NOx emission loads EGR requires.

SCR will use elements of EGR, but far less than Navistar’s system.

“There are more similarities than differences between SCR in Europe and North America,” McKenna said. “We also have experience with SCR trucks in Japan and Australia with DEF so it is becoming the global standard. It’s not really something unique to any one market.”

Other engine makers in the SCR camp shared similar sentiments.

“We have second-generation SCR technology in use already [in Europe] and it’s receiving great reviews for performance and fuel economy,” said David Siler, director of marketing for Detroit Diesel Corp. “It is the same basic technology that we will be using in North America [for] 2010. It is the only proven way to get to 2010 [standards] while saving fuel.”

DDC builds engines for Daimler Trucks North America’s Freightliner and Western Star trucks.

Ed Saxman, drivetrain project manager for Volvo Trucks North America, said, “The advantages of SCR in treating NOx is that it occurs outside of the engine, and in reducing it out there . . . we can also reduce the amount of EGR in the engine and thereby increase efficiency in that engine.”

“It’s our position that it can’t be done with EGR alone,” Saxman said. “The real reason for using EGR is not to re-burn the exhaust but to lower the temperature of combustion. EGR acts as a heat sink, lowering the engine efficiency.”

In August, Cummins Inc. reversed its original decision to use enhanced EGR for 2010 and said it would go with SCR.

“The key factor to changing to SCR was fuel,” Louis Wenzler, on-highway market communications director for Cummins, told TT. “Initially, we said that our heavy-duty product would be comparable on fuel in 2010 to our 2007 product. Advancements in SCR catalyst technology enable us to offer up to 5% fuel economy improvement for our customers — and an even greater benefit over in-cylinder solutions.”

Cummins spokeswoman Christy Nycz added that “the new Cummins aftertreatment system is much less complex than the in-cylinder approach [that Navistar is using] because the in-cylinder approach will require significant changes to the EGR system, air-handling system and vehicle cooling system.”

Meanwhile, Navistar’s Shick said though the company began with a MAN AG engine block, its 11- and 13-liter engines would use Navistar-developed EGR.

“In Navistar’s solution, a high-pressure, common-rail fuel-injection system delivers diesel in a finer mist and with improved sequencing to allow for a more efficient fuel burn,” Shick said.

“The MaxxForce’s high-strength, compact graphite iron engine block is designed to handle the higher pressures.”

A Navistar brochure says the basic principle of its 2010 system “is that fuel combustion at lower temperatures creates less NOx.”

The manufacturer said it relies on four key technologies: advanced high-pressure injection, piston bowl redesign to optimize combustion, advanced air management, proprietary electronic calibration.

“High-pressure injection at low engine speeds helps create turbulence and swirl in the cylinder for optimum air and fuel mixing, while multiple sequenced injection events help control in-cylinder temperatures and fuel consumption,” Navistar explained. That creates “a cleaner burn to reduce soot formation during combustion.”

But Mack’s McKenna takes issue with Navistar’s approach: “Simply light a candle and put it in a glass globe or container with an open top. Then gradually reduce the size of the opening, which reduces the amount of available oxygen. The flame will change color as it cools in temperature, which produces lower NOx as intended.

However, when you go too far, the flame starts to flicker as the efficiency of the combustion is reduced — and you can watch soot particles being emitted off the flame tip. This additional soot will either end up in the diesel particulate filter, requiring more active regeneration, or in the engine lube oil, with the potential for shorter drain intervals.”

Not surprisingly, Navistar sees problems with SCR.

“The other thing that EGR avoids is the risks of an SCR strategy,” Daniel Ustian, Navistar’s chief executive officer, said. “Read the label on this and it will show you that there are challenges with keeping control of using this technology: ‘Store between 23 degrees and 68 degrees.’ So essentially it says you can’t throw it outside,” Ustian said. “You can’t operate it in conditions above 85 [degrees] or below 12 [degrees]. You can, but . . . it will put the burden onto the customers.”

McKenna rejected Navistar’s claims, saying the urea tank will be protected.

“This strategy has been long thought out. Much testing has gone into it,” he said.