The Environmental Protection Agency notified four heavy-duty diesel engine manufacturers that it intends to approve some emission-control cutoffs it had earlier called into question.
The auxiliary emission control devices (AECDs) are meant to protect engines that will be built under the stringent October 2002 guidelines for emissions reduction, by shutting off or reducing emission-control devices when the engines encounter operating extremes.
In a January 2001 letter to engine manufacturers, EPA had said it was likely to approve AECDs for situations including engine starting and warmup, hard acceleration and extended idle. But the agency questioned AECDs the manufacturers wanted to protect engines in extreme cold and heat, and in high-altitude operations.
Then, in a March 4, 2002 letter sent to Cummins, Detroit Diesel, Mack Trucks and Volvo Trucks, EPA said it believed the companies’ AECDs, including the measures it questioned last year, “will not preclude issuance of certificates of conformity.”
EPA based its new position on information the engine makers had presented it since the January 2001 letter. According to EPA, each company has made progress in technical areas such as engine materials, turbocharger designs, sensor technologies and cooling systems; and this progress will minimize the use of the emission-control cutoffs EPA had been concerned about.
EPA reminded the companies that its position could change, and that it can’t give final approval to any engine company until that company applies for a certificate of conformity.