When the Environmental Protection Agency mandated a near-zero emissions standard that applied to all diesel engines manufactured after Jan. 1, 2010, RVers had many questions.
Cleaner air is great, but how do we get there? Many wondered how the new emissions standards would affect them and what they would find when they shopped for a new RV. Others asked how the diesel engines would change and what it means for future maintenance. To answer these questions, it helps to examine how and why these new standards came to be.
For years, the EPA has monitored the effects of diesel engine emissions on the environment. The new near-zero emissions standard is the result of detailed research started in the 1960s and is designed to further reduce the amount of greenhouse gas and particulate matter emitted into the environment.
Particulate matter, which includes both solid particles and liquid droplets found in the air, affects not only the environment but human health as well. The Act has been amended several times during the years to decrease the amount of gases and particulate matter from tailpipe emissions.
In 2007, particulate filters were made standard on diesel engines to achieve cleaner exhaust required at that time. The new engines will still be equipped with the particulate filter to continue to help reduce particulate matter. “The filter only needs to be serviced every 200,000 miles,” says Steve Kiray, a sales consultant with Lazydays. “Since the average RVer drives between 3,000 and 7,000 miles a year, most won’t even need to service the filter during the life of their RV.”
For those questions posed earlier concerning the new 2010 emissions standards, there are two new methods being used in addition to the filter to meet the standard for lower nitrous oxide emissions: Exhaust Gas Recirculation (EGR) and Selective Catalytic Reduction (SCR).
Exhaust Gas Recirculation System: The air comes into the intake and is passed through the turbo charger. Then, moved into the charged air cooler where the air is compressed and cooled before reaching the engine. The air passes through the engine and reaches the EGR cooler and is then recirculated back through the engine for a second time. The cleaner air is finally pushed to the exhaust manifold.
Engine System #1: Exhaust Gas Recirculation EGR, or exhaust gas recirculation, was introduced in 2002 and is already in most diesel engines. Reengineered to meet the new regulations, this method now named Advanced EGR, filters part of the exhaust back through the engine a second time. Used by Navistar, one of the largest diesel engine manufacturers, this system combines a high-pressure fuel-injection system with a valve that redirects some of the cooler exhaust back through the combustion process thereby reducing the amount of nitrous oxide emitted to almost zero.
The Advanced EGR method requires no action from the RVer and doesn’t increase service intervals. EGR does create additional particulate matter, but the new filters ensure compliance. EGR might decrease mileage slightly, depending on how the vehicle is driven. However when comparing the total fluid economy with the SCR system, the total fluid amount used by the engines is approximately the same. See the diagram to understand how the system operates.
Selective Catalytic Reduction: The DEF tank (not shown) is connected to the DEF dosing valve. When the air reaches the valve, a mist of DEF fluid is released. The urea in DEF turns to ammonia; the
exhaust and ammonia pass into the SCR catalyst, then the slip catalyst.
Engine System #2: Selective Catalytic Reduction SCR, or selective catalytic reduction, uses Diesel Exhaust Fluid (DEF), a nonflammable chemical made from urea, an organic compound found naturally in the environment. The DEF is injected into the exhaust where it breaks down nitrous oxide into harmless nitrogen. This technology has been used in Europe for several years.
RV engines made by Cummins and Mercedes use the SCR method, which requires an external DEF tank. The tank appears similar to a fuel tank where the fluid is poured in and just like a fuel tank, coaches have a monitor next to the fuel gauge to indicate when DEF fluid is needed. DEF is readily available at truck stops and auto parts retailers as well as RV service centers like Lazydays. “The process is totally transparent,” says Kiray. “And it doesn’t really add significant cost or time to your maintenance.”
The SCR device adds some weight to the vehicle, but RVers should achieve better mileage with it, which will help offset the cost of the DEF, which is comparative to diesel fuel. Manufacturers like Cummins estimate you will need approximately one gallon of DEF for every 50 gallons of fuel. Urea begins to freeze at 12 degrees Fahrenheit, but both Cummins and Mercedes have installed heating elements to prevent freezing. Because the engine will not drive without DEF, you should keep a few gallons in your storage compartment. See the diagram to understand how the system operates.
Click here to read more about Tow Vehicle and Emission Standards - New EPA Regulations Affect the Entire RV Family