EGR vs. SCR battle heats up

Christopher Goodfellow - 29 July 2010

Navistar, the only truck manufacturer to comply with EPA 2010 emissions regulations without the use of Selective Catalytic Reduction (SCR), used a public workshop to attack compliance 'loopholes' in the use of this technology.

The manufacturer presented research by environmental consulting firm EnSIGHT's that showed that when Diesel Exhaust Fluid (DEF) was not present there was little or no effect on the vehicles' operations. This included long periods of time when vehicles' Diesel Exhaust Fluid (DEF) tanks were empty or were refilled with water instead of urea, and could result in emissions ten times higher than legislated levels, according to the data.

However, Steve Berry, Director of Government Relations at Volvo Powertrain, which uses Selective Catalytic Reduction (SCR), said: "We have seen no evidence of Diesel Exhaust Fluid (DEF) refill or Selective Catalytic Reduction (SCR) tampering issues in the field and believe it is premature to impose new restrictions in the absence of any evidence of need. We question the need to make modifications to SCR strategies just six months after Selective Catalytic Reduction (SCR) products were brought to market."

Volvo's vice president of corporate communications, John Mies, added: "The fact is that a Mack or Volvo truck running at 0.2 grams (per brake hp/hr NOx) is and will continue to be much better for the environment than a Navistar truck running at 0.5 grams - and no amount of changes to the inducement strategies will change that." Navistar uses emissions credits earned in previous models to meet the guidelines, allowing its real-world emissions to be higher than the legislated limits.

In the same week Navistar attacked claims by its competitors that SCR-equipped engines offer a greater fuel efficiency than their EGR counterparts. According to tests it commissioned by the Transportation Research Center its ProStar+ and MaxxForce 13 engine consumed less total fluid, including Diesel Exhaust Fluid (DEF) and diesel, than competitors' models. This included 0.9% less total fluid than the Freightliner Cascadia with Detroit Diesel DD15 engine, which uses Selective Catalytic Reduction (SCR).

Daimler Trucks North America (DTNA) responded to the claims, attacking the testing methods: "The combination [of truck and engine componentary] chosen by our competitor does not comply with these basic premises for proper engineering work and thus doesn't provide a trustworthy result. The 440-mile test run by our competitor is not appropriate for testing modern EPA 2010-compliant trucks. DTNA's BlueTec Detroit Diesel engines regenerate after thousands of miles, not hundreds of miles. The longer the test, the more realistic the results and the closer they are to what a customer would experience in real world operation.

"It is neither appropriate nor credible to compare the 12.4L MaxxForce "mystery" engine with proven technology available in the market."

The workshop was held by the Environmental Protection Agency (EPA) and the California Air Resources Board (CARB) as a concession to Navistar dropping a law suit against the two organisation over the guidance given to manufacturers on the technology used to comply with the new legislation.

Navistar uses Exhaust Gas Recirculation (EGR) to meet the emissions targets in its new MaxxForce engines, which does not require the use of Diesel Exhaust Fluid (DEF).

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