Rolf Lockwood

January 14, 2009 Vol. 5, No. 1

Oh boy. And oh boy again. Things are getting mighty interesting on the engine front. As if they weren’t that way already.

Predictably, war is being waged along EGR vs. SCR lines. Nothing new in that, though a week ago Navistar launched something new, what it calls an “education campaign aimed at clarifying the issues surrounding 2010 emissions technologies.” The ‘MaxxForce 2010’ campaign will include customer seminars, public Webinars, and trade advertising to address “the fuel economy, cost-of-ownership and operational impacts of the competing approaches to NOx-reduction technology paths.”

As if a review were needed, but I’d better do it, Navistar is the sole engine maker intending to stick with exhaust gas recirculation to meet the 2010 emissions mandate. All other engine makers, including Hino and other Japanese manufacturers, are planning on using selective catalytic reduction, or SCR. I don’t need to go into the differences here, but Navistar continues to make the point that “advanced” EGR is the simpler solution, needing no new aftertreatment technology and no regular fill-ups of DEF (diesel exhaust fluid, or urea), while also saving weight and packaging space. Navistar’s in-cylinder EGR solution uses four key technologies – high-pressure fuel injection, advanced air management, an optimized combustion strategy, and proprietary electronic calibrations.

“Our MaxxForce 2010 education campaign will help customers understand that the best solution for 2010 does not require additional aftertreatment, and only Navistar offers that option,” says Jack Allen, president of Navistar’s North American Truck Group.

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SCR PROPONENTS, ON THE OTHER HAND, note European experience and their own testing that suggest fuel savings of 3-5% and no problems with the need to keep a little urea tank full. Also, and this is important in a bunch of cases, there will be fewer active regenerations of the diesel particuate filter.

Let’s be clear here: SCR engines will still have EGR machinery on board. The difference is that the EGR system can be scaled back, because it doesn’t have to do the whole job of reducing nitrogen oxide in-cylinder. That’s what the SCR aftertreatment catalyst is there to do. Combined, they achieve the desired result and fuel economy is apparently improved – by as much as 5% — because the EGR system isn’t trying to do it all.

And now the SCR crowd has fired another salvo, an online survey conducted by Quixote Group Research for the North American Heavy Duty SCR Stakeholders Group – that’s Detroit Diesel, Volvo/Mack, etc. There were 828 responses from a sample list provided by Heavy Duty Trucking magazine, representing both small and large fleets as well as owner-operators.

When each emissions technology was briefly described, 53.4% of the respondents said they would likely consider SCR for their next truck purchase compared to 29.4% who would likely go for increased EGR. In fact, the researchers say, 33.7% of all respondents said they’d only consider the purchase of SCR trucks compared to 10.2% who said they’d only consider the purchase of trucks with increased EGR.

The study also found that many in the trucking industry are unsure of the standards or the specific benefits provided by the two competing technologies. According to the research, only 60% of the respondents understand that nitrogen oxide is specifically included in the new EPA 2010 standards. As well, almost half of the respondents said they didn’t know which emissions technology – SCR or EGR – would deliver which benefits.

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Rolf Lockwood

Rolf Lockwood is editor emeritus of Today's Trucking and a regular contributor to

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