There is a lot going on “under the hood” as far as the EPA 2010 CARB certified diesel engines are concerned. The new emission standards have raised the bar on greener outcomes for the diesel automotive, truck and bus world. This is not an incremental increase. Both Nitrous Oxide (NOx) and Particulate Matter (PM) are reduced by 90% from 2004 levels. This overall reduction didn’t just happen overnight; manufacturers were allowed to phase-in these changes. For 2010 and beyond, all new diesel engines manufactured or sold in the U.S. must meet these emission thresholds. Read on for a look at what the standards are, how they are being met and most importantly, how they will affect you as an owner/operator.
The EPA 2010 emissions standards for diesel exhaust are: 0.2g/HP-hr NOx and 0.01 g/HP-hr PM. It seems amazing to me that such a small statement can be the cause of the tremendous changes occurring in diesel design, manufacturing and ownership. These two (further) limitations on diesel exhaust emissions are indeed the tails causing immense wagging of the dog. Let’s have a look at how these thresholds are being met and what it means to own one.
Most engine manufacturers have chosen to employ a three pronged approach to meet these lofty emissions standards. Exhaust Gas Recirculation (EGR), Selective Catalytic Reduction (SCR), and a particulate filter are all part of a system that reduces harmful exhaust gasses and products to near zero levels. Cooled EGR re-mixes exhaust with air and fuel in the combustion chamber to begin the reduction process; the particulate filter then collects and oxidizes carbon to remove PM by more than 90%. Downstream of the particulate filter the exhaust is dosed with Diesel Exhaust Fluid (DEF) in a decomposition reactor where the DEF forms ammonia through hydrolysis; this treated exhaust is then processed in the SCR Catalyst where the Nitrous Oxide (NOx) is converted to harmless nitrogen gas and water vapor. There is actually a lot more science going on, but that’s the major points of how they get there from here. Now a couple words about ownership and maintenance.
Particulate filters have been required on diesel engines since 2007. These filters need to regenerate from time to time, meaning they burn off the collected PM and rejuvenate the filter. This can be done passively, while driving the vehicle hard enough to get the exhaust gas temperature up, or actively by pressing the active regeneration button on the dash while you are off the road. Pretty simple, but it will become a regular part of the operator’s routine.
The DEF tank will contain up to 15 gallons of fluid, purchased from various outlets in varying quantities, which will need to be replaced from time to time. Rule of thumb would say you should get approximately 500 miles to a gallon of DEF, so replacing it won’t be a constant pain but there are considerations. Performance will be affected when the DEF tank goes empty, to the point where the engine will not restart without replenishment. There are indicators on the dash to monitor the situation, but it would be wise to carry a gallon or two onboard to avoid the inconvenience of running out and getting stuck.