Maintenance: Going RETROfit

Today’s trucks and new equipment produce a fraction of the exhaust emissions of models sold just five years ago. But for air quality regulators in many areas of the country, that’s not enough.

While there is no federal requirement to clean up older diesel engines, many states are moving towards these goals and several cities and departments of transportation are putting diesel emissions reduction requirements in their bids. This trend is emerging mostly from places the Environmental Protection Agency considers air quality “non-attainment areas,” essentially big cities that haven’t met their air pollution reduction goals. And while the specific regulations vary from state to state and sometimes city to city, the total impact covers a big swath of the country – almost all of California and most of the big cities on the Eastern Seaboard and in Texas. Diesel emissions reductions have also been mandated in the bid specs for specific jobs as well, including the Dan Ryan Expressway in Chicago and Boston’s Big Dig.

There are several ways to clean up your equipment’s emissions. You can sell the old equipment and buy new. Or you can put a new engine in your old machines – called repowering. But the least expensive solution is to outfit your older equipment with a diesel exhaust retrofit. In an exhaust retrofit you replace the muffler with a more technologically sophisticated emission control device.

But the process of choosing the right technology to meet your local rules and regulations is complicated. “We’re certainly contributing to the education of the customer base,” says Chris Milani, president of Fleetsource, an OEM authorized diesel fuel system remanufacturing company that has also expanded into the diesel emissions field. “The process is very hands on and requires a lot of resources and communication. That’s kind of unexpected for most people. They don’t realize the intensity of the process.”

California’s new rule
On July 26, 2007, California’s Air Resources Board approved a regulation to reduce emissions from existing off-road diesel equipment used in construction, mining and other industries. While the impact of this regulation is limited to that state and out of state contractors working in California, it is also being viewed as a standard that other regions or regulatory agencies may adopt in the future.

The regulation requires each fleet to meet what the state determines as the fleet average emission rate targets for particulate matter, or apply the highest level of verified diesel emission control systems to machines that equal at least 20 percent of the fleet’s horsepower.

Additionally, large and medium fleets are required to meet the fleet average emission rate targets for nitrogen oxides or to turn over a certain percentage of their horsepower each year. By “turn over,” the state means replacing a piece of equipment with a new machine, repowering, or designating a dirty machine as a low use unit and restricting it to no more than 100 hours of use a year. The dates of compliance are scheduled according to the fleet size in horsepower.

  • Large fleets, those with machines totaling more than 5,000 horsepower, will have their first fleet average compliance dates in 2010.
  • Medium fleets, those with between 2,500 and 5,000 total horsepower have their first compliance dates in 2013.
  • Small fleets, those with less than 2,500 horsepower, have their first requirements in 2015.

Credit will be given to contractors who repower a Tier 1 or higher engine before March 2009 and fleets that retire their Tier 0 vehicles at a rate of 8 percent of horsepower per year between March 2006 and 2009. The regulation will also require contractors to begin reporting their horsepower and emissions control status starting in 2009.

Retrofit technology
There are a number of companies such as Caterpillar, Cummins, Donaldson and lately Komatsu, making exhaust retrofit devices. The type of device you need will be dictated by the age of the engine, the application and the degree to which your local regulators expect you to cut emissions.

  • DOCs
    Diesel oxidation catalysts are the most common and least expensive solution. They use precious metals to oxidize carbon monoxide, hydrocarbons and organic particulate matter as they flow through the device. DOCs don’t require ultra low sulfur fuel either, making them well suited for off-road equipment. They range in efficiency from 10 percent to as high as 40 percent depending on the engine, application and other variables.

    Caterpillar’s version is what it calls a catalyzed converter muffler or CCM. It’s offered on new equipment and for retrofits. “It consists of a diesel oxidation catalyst within a muffler configuration to provide exhaust, noise and emissions control in a single unit, says Ken Katch, Caterpillar emissions solutions group director. “With this design approach there is no need for modifications to the exhaust system, since the CCM is usually a direct fit replacement for the original muffler. CCMs can generally be installed on any type of diesel engine regardless of size or application,” he says.

  • DPFs
    Diesel particulate filters contain a honeycomb filter section to trap exhaust particles and periodically incinerate them by one of several means.

    Like DOCs, passive DPFs use precious metals to catalytically burn up particulate matter automatically and continuously when the exhaust stream reaches a certain temperature. Donaldson markets standard and low temperature options. Active DPFs use either a shot of fuel or an electric heating element to oxidize the pollutants.

    DPFs are typically heavier and larger than the mufflers they replace and require occasional maintenance to clean out accumulated ash. They are more efficient in removing more exhaust pollutants but they also require the use of ultra low sulfur diesel fuel.

    “DPFs need to be matched to the engine and machine application before they can be used,” Katch says. “DPFs may cause a higher backpressure level than the original muffler so there may be a small fuel consumption penalty.”

    In addition to its line of DOCs and DPFs, Donaldson makes a product that in terms of efficiency ranks somewhere in-between called the DMF, that catalyzes and filters. “DOCs are good, DMF is better and DPF is best,” says Fred Schmidt, director of the company’s emissions group. “A DOC is typically 20 to 40 percent efficient. A DMF is 60 to 70 percent. You might choose a DMF because it can operate effectively at lower temperatures than a DPF without plugging or ash cleaning,” he says. It can also handle a higher soot load than DPFs, making them desirable for high-soot applications like older engines and off-road equipment. The product is also constructed of metallic filters, increasing the durability, he says.

  • NOx
    Lean NOx catalysts are similar to DOCs in that they use catalytic materials, but they also employ fuel sprayed into the canister from upstream as a liquid reductant to trim NOx emissions. They are often used with DPFs to cut both types of emissions.

    Selective Catalytic Reduction, as the name implies, is also a catalyst-based system, but uses liquid urea as the reductant to cut NOx. Many engine manufacturers plan to use the urea-based SCR technology in their 2010 engine designs, but until then the urea supplies may be challenging to obtain and kept on an individual basis. While effective, SCR retrofit devices may pose installation challenges, says Hans Egger, director of engineering for Fleetsource. “You need additional equipment for the urea, like tanks, valves, controls and so on, and this will require significant installation and application expertise,” he says.

The costs of diesel exhaust retrofits vary greatly and depend on the type of technology chosen, the horsepower of the engine and the amount of emissions the regulatory authorities expect you to eliminate. For trucks, at the low end of the scale a simple DOC installed may run from $500 to $2,000, says Joe Kubsh, executive director of the Manufacturers of Emissions Control Association. DPFs range from $7,000 to $10,000. SCR costs range anywhere from $12,000 to $20,000 with a DOC, and $15,000 to $25,000 with a DPF. Lean NOx catalysts with a DPF go for $15,000 to $20,000. Costs for off-road equipment may run higher than these figures due to the higher horsepower and dirtier exhaust streams of the engines, Kubsh says. On some high horsepower engines dual DPFs may be required Schmidt says.

Despite these sobering prices, in many cases the retrofits may make the most economic sense. The only other way to meet regional exhaust emissions targets – repowering with a new engine – will in most cases cost twice as much as an exhaust retrofit.

Caterpillar offers customers of certain engines some middle ground between an exhaust retrofit and a full repower. The Cat Engine Upgrade Group takes an existing Cat engine core and replaces the pistons, liners, turbos, fuel injectors, fuel pump and other components. The end result brings its 3306 and 3406 engines from unregulated up to Tier 1 emissions standards, says Katch.

Funding … for now
For off-road equipment in many markets, diesel exhaust retrofits may qualify for government funding to help offset the costs of the installing the technology on older machines. “There are several pots of money available for contractors to use to retrofit equipment,” Kubsh says. “Right now California and Texas are leading the way.”

The details of the funding programs vary between different regions. For example, Texas is funding retrofits that that help cut down on NOx, but has little interest in funding reductions in PM. That’s because NOx is a leading cause of ground level ozone, a major air quality problem in the big cites of Texas. Volatile organic compounds (VOCs) and carbon monoxide (CO) may also be targeted, depending on the region.

California’s retrofit grants are designated for voluntary efforts at present, but all the funding goes away once the state Air Resource Board’s rules on diesel exhaust retrofits become mandatory in 2010. After that, contractors will have to pay the entire cost of retrofits out of their own pockets. The state’s Carl Moyer Program makes more than $140 million available through local air quality districts. The federal EPA is also working on proposed legislation that would double the amount of grant money made available for diesel exhaust retrofits, Kubsh says. For more information see the “Resources” box on page 41.

Crankcase ventilation filters
While crankcase ventilation emissions coming out of an engine’s blowby tube don’t qualify as “exhaust” emissions, they are a form of air pollution nonetheless and are drawing the attention of regulators.

In the past, crankcases were ventilated to open air, but accounting for crankcase emissions became mandatory with the new 2007 on highway engines. Now Donaldson and other manufacturers are manufacturing these as aftermarket products to use in retrofits of pre-2007 engines.

“The market doesn’t know a lot about crankcase emissions, so there is definitely growing interest in that area,” says Donaldson’s Fred Schmidt. Because off-road engines generally create more tailpipe pollution in general, the impact of reducing crankcase fumes is not as significant for off road as it is for on road, he says.

The Donaldson product, called Spiracle, captures the gases that leak past the piston rings and directs them into a two-stage filter. The first filter stage coalesces the vaporized lube oil; the second is more of a traditional filter that traps particulate matter, Schmidt says. Once past the filters, the cleaned air is then routed back to the intake system. The Spiracle system has no effect on oil change intervals and the filters are changed whenever the lube oil is changed. Donaldson is waiting for EPA approval on the next version of Spiracle, which will require filter replacement every other oil change, Schmidt says.

The Diesel Technology Forum’s Retrofit Toolkit includes information on the technology, funding, cost effectiveness, implementation issues and how to get started on a retrofit project. At:

The EPA and ARB publish a list of verified diesel emissions reduction retrofit devices that have undergone rigorous testing and are approved for use. These can be found at: and

To find funding for diesel emissions retrofits there are several sources. From the EPA, check out: The Federal Highway Administration has its Congestion Mitigation and Air Quality program: More about California’s Carl Moyer Program can be had at For the Texas Emissions Reduction Plan, go to:

For general information and current news, white papers and case studies regarding retrofits, check out MECA’s website at:, and

California provides several websites to help contractors become familiar with its diesel emissions reduction plan. For general information or access a spreadsheet fleet average calculator, go to: