EL MONTE, Cal. –Navistar has formally voiced concerns over “compliance loopholes” that it says may be exploited by truck and engine manufacturers using selective catalytic reduction (SCR).

Navistar, which is the only North American truck and engine maker to avoid SCR in 2010, has complained to the EPA and CARB that regulatory loopholes allow engines with SCR to operate without diesel exhaust fluid in certain situations, potentially exceeding stringent NOx limits. The manufacturer first launched a lawsuit against the environmental groups and then later dropped the suit when the groups agreed to work with Navistar to reach an acceptable solution through joint workshops. The first such workshop was held July 20.

“Navistar first identified these loopholes to the agencies and also presented our concerns at today’s workshop,” said Jack Allen, president of Navistar’s North American truck group. “We will be working with the EPA and CARB to ensure full environmental compliance.”

During the recent workshop, Navistar expressed concern that engines using SCR can increase NOx emissions tenfold when urea is not present. It presented research conducted by EnSIGHT as evidence.

One truck tested by EnSIGHT appeared to operate indefinitely with water in place of diesel exhaust fluid, Navistar pointed out. It claims the truck ran 13,000 miles with essentially no NOx control.

Citing European research, Navistar also complained that even when DEF is present, a truck in stop-and-go traffic may not generate high enough exhaust temperatures for the SCR system to function properly, again emitting higher than acceptable levels of NOx.

“Truck owners are paying a substantial price to comply with 2010 NOx requirements,” said Allen. “They, and the public, deserve to know that the new equipment they are purchasing actually works as promised to curb pollution. It’s obvious, however, that these trucks can operate effectively without liquid urea, and that under these and other conditions, SCR NOx emission control is turned off. We’re calling on the EPA and CARB to assure that all vehicles, not just ours, work when they are supposed to be working.”

Also present at the workshop were manufacturers using SCR, including Volvo Group. Volvo officials expressed disappointment that the rules were under review just months after the successful roll-out of EPA2010-compliant engines.

“We question the need to make modifications to SCR strategies just six months after SCR products were brought to market,” said Steve Berry, director of government relations with Volvo Powertrain. “These strategies were thoughtfully developed in good faith by EPA, CARB and EMA, applying their collective best judgment to balance SCR operation with other critical issues, not the least of which is safety.”

Volvo raised the point that unjustifiably limiting engine torque excessively could cause safety concerns on the road or strand drivers in the middle of nowhere in adverse conditions.

Berry went on to say “We have seen no evidence of DEF refill or SCR tampering issues in the field and believe it is premature to impose new restrictions in the absence of any evidence of need.”

John Mies, vice-president, corporate communications with Mack and Volvo called out Navistar for demanding the workshop in the first place.

“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,” he said in reference to Navistar’s use of credits. “Let’s make sure that what we do is truly in the interest of the environment and the public. And let’s not penalize those who have worked with you in good faith, and reward those who are trying to manipulate the system for their own competitive advantage.”

Volvo Group has already delivered more than 3,500 Volvo and Mack engines with SCR in North America and has received orders for more than 10,000.

Daimler Trucks North America (DTNA), parent company of Freightliner Trucks and Detroit Diesel, also defended the use of SCR at the workshop. Its message was that SCR is proven to be effective, having accrued more than 30 million test miles and popular with customers, having received over 25,000 orders for EPA2010 vehicles.

“DTNA’s BlueTec emissions systems operate as designed, meeting federal and state air quality standards that reduce particulate matter and nitrogen oxides to near-zero levels without the use of credits,” the company said in a statement released to media after the workshop. “DTNA testing and customer experiences also validate that DEF refilling inducements work to consistently and effectively keep each DTNA vehicle operating in compliance with 2010 emissions standards.”