WASHINGTON – The EPA dismissed Navistar’s bold claim that its rivals’ SCR engine systems are routinely ‘tricked’ and circumvent the 2010 emissions regulation, but the agency did propose tougher guidelines for those engines.
In a proposal released earlier this month, the Environmental Protection Agency said technical developments in SCR systems justify stricter standards for monitoring DEF (diesel exhaust fluid) levels and warning indicators when tanks run down.
Specifically, the EPA proposed requirements for warning drivers when they are running low on DEF; slowing the truck down to 5 mph if the DEF is near empty or the DEF dosing system is not working properly; and require the system to identify and respond to poor-quality DEF and have better tamper resistance.
However, the EPA also ruled that so far SCR engines have been effective at meeting the emission standards, despite Navistar’s contention that by allowing ‘compliance loopholes‘ the agency is giving its competitors a licence to pollute."
(Navistar — the only major engine OEM not using SCR in new trucks – has gone as far as calling for SCR trucks to be recalled).
The EPA stated it does not believe that the rules are easily or routinely bypassed by drivers who supposedly fail to fill up with DEF or substitute other liquids like water in the tank – as Navistar alleged in a study it commissioned.
EPA said the charge does not "reflect the overall efficacy of SCR systems on heavy-duty diesel engines currently in operation or the way they are actually used" and that the overwhelming majority of drivers comply with the DEF requirement.
"While it is possible that drivers could intentionally take such actions … the manner of truck operations conducted in the Navistar study is clearly not representative of the vast majority of truck operations."
However, the agency acknowledges that new sensors are better able to detect poor quality DEF or non-DEF and alert drivers through dashboard messages and and audible signal. As well, a quicker "derate" inducement procedure to 5 km/h when DEF runs too low could also be in order.
A possible alternative would be to either shutdown or idle the engine if the DEF tank runs empty or isn’t dosing properly.
The deadline for comments to the proposal is July 7.
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