“ engine’s aftertreatment system may be unable to properly manage the engine’s drop in performance. But when that happens, the DPF is likely lower on the list of concern than a coming engine overhaul. Coolant leaks, oil leaks, failed injectors, and dirty intake air can create aftertreatment issues,” says Ray Hasting, Mack Trucks’ director – e-mobility and national vocational accounts. “Loose exhaust clamps create the highest frequency of active regens. This affects how well the diesel oxidation catalyst will convert gases, as well as the DPF’s ability to regenerate the soot into ash. “We see oil leaks poisoning and deactivating the precious metal coatings,” Deayton agrees, referring to the upstream issues. If the regen activity seems excessive, it’s time to look upstream for the root cause of the problems, such as oil leaking from the piston rings, or other leaks in the combustion chamber, Agebrand says. Restricted exhaust flows can shift a filter’s substrate or lead to a crack or outright break in the material, adds Cory Just, Navistar’s director – dealer field service.Īn active regen’s high heats can even create problems of another sort, as the otherwise fluffy ash sinters and fuses into ever-tougher blocks that are difficult to clear away. “This will cause accelerated wear on the turbo seals valves,” says Ralph Deayton, operations manager at the DPF Company, which cleans and restores such filters. Sustained back pressures can lead to several issues, too. And once the filter becomes too restricted with anything – the unaddressed soot, or even the resulting ash – the engine will de-rate, leaving drivers with just enough power to limp off the road. Ignore the warning lights that call for the added heat, no matter the truck’s application, and the back pressure begins to climb. “Even when we call an engine hot, it’s many times not hot enough for a DPF … It’s a lot of heat, and really the only way Class 8 engines get there is you need about a 50% workload or more for some extended period of time, like 30 minutes or more.” “You’re looking at 250-300 degrees Celsius for this regen operation,” Agebrand says. Even coolant heaters and pre-heaters that help to crank engines in frigid temperatures will fall short of DPF needs. Indeed, there is no substitute for this all-important engine heat. This filter has put in 760,000 miles of service. “It’s just a question of temperature.” A DPF is designed to last at least 400,000 miles. But lighter loads, extra idling, excessive horsepower, or heavy stop-and-go traffic will typically require parked trucks and more of the “active regens” to tackle the contaminants. Most maintenance headaches are linked in some way to the underlying “regeneration” process that reduces soot, oil, fuel from failed injectors, or leaking coolant into the ash laden with nothing but oil additives and wear metals.Ī heavily loaded over-the-road engine generates much of the heat needed for the “passive regens”, requiring drivers to take little action. Filter-fouling sulfur levels are now a distant memory.īut there’s only so much a well-engineered ash can can do. Many of the earliest failures had more to do with limited supplies of ultra-low-sulfur diesel, he adds, referring to the fuel change that emerged with the aftertreatment systems in 2007. “The DPF, to some extent, has had a little bit of a bad rap,” offers Johan Agebrand, director – product marketing at Volvo Trucks North America. Black smoke that once spewed from exhaust stacks is largely a thing of the past thanks to these devices that stand guard against particulate matter. They get no respect - at least, not the respect they arguably deserve. Diesel particulate filters could be considered the Rodney Dangerfield of truck components.
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