January 2008 - Feature
What Fleet Managers Should Know About Diesel Particulate Filters
By Sean Lyden
Button Push Activates Parked Regeneration
Parked regeneration is a form of active regeneration in which the driver must park the vehicle and initiate the regeneration process by pushing a button on the dash.
This process does not pertain to light-duty pickups and vans with 2007-compliant diesel engines. However, most medium-duty trucks are equipped with dash indicators alerting driver of the need for parked regeneration (also known as manual regeneration). The process takes approximately 20-40 minutes to complete.
How often is the parked regeneration process required? According to Bob Aquaro, vice-president of product assurance with Mitsubishi Fuso Truck of America, very few applications require parked regeneration. "If you had a truck in ultra-low speed mode, a truck that never got over 25 miles per hour, that would be an instance for manual regeneration," advises Aquaro.
What happens if the driver ignores warning indicators? A "Driver Interface" document created by International Truck and Engine Corporation puts it this way: "WARNING: Failure to alter the duty-cycle or initiate manual regeneration will cause engine to lose power (and therefore limit vehicle speed) and eventually stall out engine, which could cause an accident. . . Failure to abide by these instructions may result in severe loss of power, engine vehicle speed and may cause an accident or a fire."
What’s Involved in DPF Maintenance?
Although the DPF is designed for long life, eventually the accumulated ash must be removed by special cleaning equipment. What is the typical cycle for the DPF before it needs to be cleaned? "We’re looking at least 100,000 miles before having to worry about it," projects Aquaro. Engine manufacturer estimates range from 100,000-150,000 miles in most light- and medium-duty applications.
"The question then becomes do we clean (the DPF) or do we offer a DPF exchange program, replacing it all together?" poses Aquaro. The answer is manufacturer- and truck class-specific. Fleet managers should consult the manufacturer’s rep to determine the cleaning/replacement processes for specific trucks.
What costs should can be expected for DPF cleaning/replacement? Estimates range from several hundred dollars to $2,500 and more.
Fuel, Oil, and Oil Change Intervals Can Impact DPF Life
Here are factors to consider to maximize DFP life.
- Fuel. Too much soot leads to premature clogging and change cycles for the DPF. One way to counteract this issue is to focus on removing any controllable sources of soot or particulate matter.
One particular controllable source is the amount of sulfur in fuel. And this is where ULSD comes into play because its sulfur content is only 15 parts per million (ppm), down from the 500 ppm in the previous low sulfur fuel.
A Frequently-Asked-Questions document, produced by International Truck and Engine Corporation and posted on the Ryder Truck Leasing Web site, www.ryder.com, says this: "Misfueling once or twice won’t create problems; however, continuous use of diesel fuels containing more than the recommended 15 ppm of sulfur will cause a poisoning effect of the catalyst in the exhaust system and ruin the emissions system, causing the vehicle to break down with costly repair implications and void warranties."
"Anything that goes into the fuel tank," Aquaro warns, "will impact the DPF. So make sure you’re putting in the right fuel."
- Engine oil. To meet 2007 emissions requirements, engine oil manufacturers have developed a new standard: CJ-4. The standard for pre-2007 oils is CI-4 Plus, which was designed to meet 2004 EPA regulations.
What makes CJ-4 more compatible to 2007 engines? The difference is lower levels of phosphorous, ash, and sulfur. If used in 2007 engines, these additives could prematurely plug up the diesel particulate filter (DPF), increasing maintenance issues.
What are the risks if the previous standard, CI-4 Plus, is used in a 2007 engine? "You may find that you have to replace the DPF at a much earlier than anticipated time," says Dennis Bachelder, senior associate for Engine Oil Licensing and Certification at API, with over 25 years experience in the areas of fuels, lubricants, and exhaust emissions. "You then face performance problems as a result of any backpressure from a plugged-up DPF."
Would this practice void engine warranty? "It’s a risk, but that’s the call made by the engine manufacturer on a case-by-case basis. But one thing’s for sure: replacing the DPF is not cheap and will result in performance problems and cost issues incurred by downtime for the repair," Bachelder explains.
- Oil change intervals. "Abide by manufacturer oil change intervals," Aquaro advises. "That can have a huge impact on DPF longevity. If the manufacturer says to change oil at 6,000 miles, you should change it at 6,000 miles. Those numbers aren’t just pulled out of the air. Engines are tested extensively to arrive at those intervals." WT