To meet stringent, near-zero emissions standards set by the U.S. Environmental Protection Agency, the vast majority of trucks sold after January 1st will be equipped with Selective Catalytic Reduction (SCR). This technology uses a catalytic system - which includes diesel exhaust fluid (DEF) - to treat exhaust and reduce it into simple nitrogen and water vapor.
"The exhaust coming out of a 2010 heavy-duty diesel engine with an SCR platform has near-zero regulated amounts of exhaust gas," reports David McKenna, director of powertrain sales and marketing, Mack Trucks. "It is hard for us to even measure this stuff in a lab."
The particulate matter emitted is 0.2 grams per brake horsepower hour. (For reference, this is equal to 1/2270th of a pound.) "If you look inside the exhaust stack, there is no soot," says McKenna. "In 2010, we are essentially neutralizing the oxides of nitrogen into simple nitrogen (N2) and water vapor (H2O). It is almost immeasurable amounts of other gasses that are coming out. It is an ultra-clean engine."
SCR technology requires virtually no changes to existing base engines. However, the material used in the catalytic converter is expensive, which adds to the initial purchase price. For instance, let's look at the offerings from Daimler Trucks and Mack Trucks.
Emissions technology surcharges for Freightliner trucks equipped with Detroit Diesel DD15 and DD16 big bore engines, as well as the medium bore DD13, will be $9,000 per vehicle. A surcharge of $7,300 will be added to vehicles equipped with the Cummins ISC8.3 engine, and a $6,700 surcharge will be added to the price of vehicles equipped with Cummins ISB6.7 engines.
The price increases at Mack are very similar. "We are going to be in the $9,600 range for conventional [Class 8 trucks] and around $10,000 for the TerraPro cabover [truck]," says McKenna.
Despite these initial purchase price increases, the long-term performance gains promise a return on this investment. "SCR is the only emissions technology in decades proven to be as good for business as it is for the environment," says Mark Lampert, senior vice president of sales, Daimler Trucks North America. "We are pleased to deliver a proven solution that gives our customers a return on their emissions technology investment."
Payback in fuel savings
According to Daimler Trucks, SCR treats NOx emissions downstream in the exhaust so that the engine can be tuned to run more efficiently and economically. "SCR is the only technology that will provide significant fuel savings to our customers," Lampert asserts.
"Any time you purchase diesel fuel, you are going to see an immediate payback," McKenna asserts. "Are you going to see the payback to the degree you would with the volumes of fuel a highway truck goes through vs. a vocational truck? No, but the interesting takeaway with SCR technology is that the harder you work the engine, the better the fuel economy is relative to the same engine with the same duty cycle of 2007 to 2010."
He explains, "With a typical vocational truck, you need a lot of power (high torque) at very low [engine speed], which can mean a lot of NOx production. If we can neutralize the NOx after the fact, that allows us to dramatically improve the fuel economy and still dose well below the 3% rate we've claimed for diesel exhaust fluids." Consequently, the fuel economy improvement on a percentage basis is actually better than that of a highway truck.
"One of the by-products of allowing the engine to breathe a little better instead of choking it off with massive rates of EGR is the soot loading of the lube oil from the combustion is much less," McKenna notes. "You are not getting the soot loading on the cylinder walls that you had yesterday. We have actually lowered the rate of exhaust gas recycling, allowing more oxygen in the cylinder so we are getting more thorough combustion. So you are not getting the soot deposits that the industry was having historically with higher rates of EGR."