Issue link: https://read.dmtmag.com/i/74547
HOW TO SPEAK DPF Dirty exhaust enters the DPF, and soot is trapped on the coated ceramic honeycomb material inside the filter, rendering the exhaust exiting the filter clean. Still, as with any truck component, failures can happen. If you understand DPF maintenance cycles, you'll have a better idea of when you need to get help and when you can get back to watching the scenery. What does a diesel particulate fil- ter do? The U.S. Environmental Protection Agency's 2007 diesel emis- sions regulations required a major reduction of particulates in diesel exhaust smoke. Any truck manufac- tured after Jan. 1, 2007, has a DPF. Most heavy-duty engine makers later added selective catalytic reduc- tion, along with a DPF, to help meet the more stringent requirements of the 2010 emissions regulations. Smoke is smoke. It just floats away, right? There's actually a lot of heavier- than-air stuff in diesel smoke. EPA calls it diesel particulates. You and I would call it soot. These are fine and ultrafine particles of elemental carbon with adsorbed com- pounds such as sulfate, nitrate, metals and organic compounds. And this soot is bad for us? Yes. EPA says diesel particulates are "likely" car- cinogenic. Other agencies, such as the World Health Organization, have gone further than "likely." EPA cites tests showing an increased risk of disease, 42 | Overdrive | August 2012 mostly notably lung cancer, due to long- term exposure. What does a DPF look like? A DPF is not a spin-on type filter like an oil filter or a cartridge-type like a fuel filter. The ceramic filter itself, about the size of a five-gallon bucket, sits in a metal canister that also acts as a collection device for soot. The DPF is found downstream from the engine in the exhaust system. When the DPF starts clogging up, does that impact my vehicle or engine per- formance? Much like a clogged catalytic converter on your car, a plugged DPF interferes with efficient exhaust flow. It can lead to compression or combustion problems if left untreated. In most cases, the DPF burns off accumulated soot through either a "passive" or "active" regeneration. In a passive system, the engine's computers track certain variables – like emissions of nitrogen oxides (NOx) and temperatures – and heat up the DPF to oxidize (burn off) the soot. In an active regeneration, diesel fuel is directly injected into the exhaust stream, usually right behind the turbocharger. This fuel evaporates and coats the DPF catalyst, causing a chemical reaction to oxidize any remaining soot, leaving a residual amount of ash. Either event is likely the reason that dash light came on. Cool. So I really don't have to worry about it all? It depends. If the light is blinking, you don't have to worry. If the light comes on and stays on, it's time to get the DPF cleaned. Isn't cleaning what the regeneration process does? The regeneration process burns off accumulated soot, but it does not clean out the actual filter media that trap the particulates. And because the regeneration process will not burn off all the ash, eventually it will collect in the canister and fill it up. This nor- mally happens around 400,000 miles for heavy-duty engines. But if you have a turbocharger or fuel injector failure, it could lead to the filter media becoming saturated before the mileage interval is met. So the little DPF light might indi- cate a bigger problem, depending on the mileage since the last cleaning. Would that be an emergency situation? It's not an immediate issue unless you're around the 400,000-mile service interval. Usually you'll know you're getting close because the regenerations will be get- ting more frequent. If you notice more and more lights and regenerations well before 400,000 miles, you may have a bad injector or turbo. In any event, if you wait too long, your performance will fall off noticeably as the engine de-rates due to excessive exhaust back-pressure. So it pays to get the DPF looked at as soon as possible when regens are too frequent or the cleaning warnings are too early. How long does cleaning take? There are two types of cleanings and both need to be done by a certified DPF technician. If you need to change out the DPF – usually because it is chipped, cracked, burned or melted – it takes about 2.5 hours, depending on vehicle or engine make. If your DPF is in good shape and just needs to be cleaned, you're probably looking at four to five hours. Some manufactur- ers have quick exchange programs whereby you trade out your dirty DPF for a clean one. How much does it cost? It's not cheap. A DPF cleaning machine costs about $75,000, which helps explain why get- ting the unit cleaned can run you about $500. If you're replacing the DPF, you're probably looking at $1,200. Can I just do it myself? You could, but it's not recommended. The DPF element is made of fragile ceramic material, so you don't even want to bump it. A non- core replacement DPF can cost as much as $4,500. Editor's note: Mack Trucks, Cummins, Detroit and Navistar contributed to this story. Cummins