What is in this article?:
EGR vs. SCR
Manufacturers have employed one of two engine technologies to achieve Tier 4i requirements, both of which involve, for the first time, engine after treatments. Some manufacturers, including John Deere and Cummins (which makes engines for Versatile), are using cooled Exhaust Gas Recirculation (EGR) to reduce NOx inside the combustion chamber and a diesel particulate filter (DPF). The DPF replaces the muffler to capture particulates, which then have to be burned off through a regeneration process. Some experts question whether this process will affect vehicle operation.
Other manufacturers, including AGCO, Case IH, and New Holland, are employing Selective Catalytic Reduction (SCR) to achieve the required levels for high-horsepower equipment. This method treats exhaust gases post combustion, or after they leave the engine, with a fluid blend of urea and water, called diesel exhaust fluid (DEF).
These are the same two methods being used this year in diesel-powered cars and trucks to achieve similar emission reductions on the highway. Both methods work. But which one is better for buyers depends on whom you ask, according to Jim Mele, editor-in-chief of Fleet Owner.
“There are so many claims flying back and forth,” Mele says. “It is like a scorched earth policy between the manufacturers right now.”
Mele says that some tractor manufacturers claim that SCR offers better engine efficiency and fuel economy because it treats emissions separate from engine function. The drawback, he says, is that you have to carry DEF, which costs about the same per gallon as diesel fuel.
“The other method, EGR, doesn’t require you to add a second fluid,” Mele says. “But those against it will say it burns more fuel and shortens service intervals. It’s a he-said, she-said kind of thing.”