Diesel Repair: DPF (aka Diesel Particulate Filter) Part II

We are continuing with the theme of diesel particulate filters. In Part I we discussed the purpose of DPF and how it must meet the industry standard emissions regulations. More diesel service centers are finding that drivers are in need of diesel repair for problems created by a disengaged DPF.

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To help diesel vehicle owners understand the importance of the DPF, here is a brief explanation as to how the DPF works to control exhaust emissions.

Active vs. Passive -- Manufacturers use one of these two approaches to regenerate DPFs.

Passive Regeneration: Passively regenerating DPF systems are commonly found in the retrofit marketplace for construction equipment. In these applications, the vehicle's duty cycles and temperature profiles can be observed prior to filter installation. Passive systems rely on precious metal-coated substrates to heat the normal exhaust flow to temperatures that trigger regeneration. Although more sensitive to duty cycle and temperature, once installed, these DPF systems are considered to be more user friendly, as they do not require fuel additives, have no moving components, and only need to be serviced for annual cleaning.

Active Regeneration: Light diesel trucks have very different duty cycles. Active regeneration is employed when the exhaust temperatures are too irregular for a passive system to regenerate consistently. Active regeneration is accomplished by changing parameters in the engine to increase the exhaust temperatures in the DPF. This requires precise knowledge of engine parameters and access to the engine control unit. Because of this, the engine management approach is performed by the OEMs that have direct access and control over their engine design. Among the active strategies used are: late or post-injection of fuel into the combustion chamber, changes to the turbo boost, changes to the EGR valve, intake air throttling, and retarding the injection timing. All these methods can raise the exhaust temperature, but they also have negative impacts on the vehicle's fuel economy, power, and engine wear.

Filter Regeneration vs. Cleaning: Every DPF has what's called a wall-flow filter positioned in the exhaust system. As the exhaust gases pass through this filter, emissions of particulate matter, carbon monoxide, and hydrocarbons are trapped in the filter and reduced by more than 90%. This trapped diesel particulate matter settles inside the filter walls until temperatures reach levels that allow for combustion. The process of combusting these trapped particulates without an intolerable buildup of engine backpressure is called filter regeneration. The process of cleaning the DPF involves taking the filter out of the exhaust system and putting it in a special cleaning chamber.

For more questions about the purpose of the DPF, and for any problems it may cause, be sure to ask your diesel repair specialist.

In need of diesel repair? Contact our ASE Certified Technicians at Wentland Diesel Service by calling 541-938-3875 or go on-line at http://www.wentlanddiesel.com/ for more information. Our auto shop provides car and truck repair, including diesel service, to the vehicle owners in   Milton-Freewater, OR, Walla Walla, WA, Pendleton, OR and surrounding areas.

Engine Repair: DPF (aka Diesel Particulate Filter) Part I: A Ticking Time Bomb!

Many vehicle owners don't give much thought about engine repair until they start to notice problems in their vehicle's performance on the road. These problems include the issue of emissions control. No one has ever said, "I wish this air was a little less clean." But some diesel vehicle owners are known to remove or tamper with their diesel vehicle's exhaust particulate filters. Because of this, vehicle emissions regulations have become stricter as time goes by. That means all newer diesels (2007 and newer) sold for on-highway use are required to have functioning emissions equipment. However, auto shops are reporting that they are seeing more and more owners of diesel vehicles coming in for engine repair because they have either removed, or tampered with the exhaust particulate filter.

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History Is Repeating Itself

In the 1960s, automotive emissions were nearly unregulated. In order to reduce air pollution, America decided to mandate vehicle tailpipe standards that were radically cleaner than before. The new laws didn't specifically require manufacturers to add catalytic converters and air injection systems—but that's the technology automakers chose to meet the new standards. Back then, vehicle enthusiasts felt wronged by the new hardware that showed up under their cars. They complained about reduced fuel economy, overheating, too much complexity, and poor vehicle performance. The catalytic converters, EGR components, and air pumps made working under the hood much more difficult—so hard-core enthusiasts ended up removing them.

But then what happened? Those same diesel vehicle owners were scheduling an engine repair or a more major engine rebuild, including the diesel particulate filter (DPF), to take care of engine performance problems. A wise vehicle owner will find out what the DPF does, and what it costs to replace before tampering with it.

What is the role of the DPF?

All engines emit pollutants (i.e., chemicals and compounds created by our vehicles that end up in our air that shouldn't otherwise be there) into the air we breathe. To reduce the amount of these pollutants, newer diesel engines have been fitted with a filter in the exhaust pipe to capture soot particles. This matrix of materials (a composite of cordierite, silicon carbide, or metal fibers), called a diesel particulate filter (DPF), traps the particulates (soot) flowing out the exhaust pipe. DPFs capture soot until they fill up and create too much backpressure. At that point, DPFs can regenerate (clean) themselves in one of two ways: active or passive.

Watch for Part II coming soon in which we will describe Active and Passive Regeneration in more detail.

Is your diesel particulate filter leading you to a premature engine repair or major engine rebuild? Contact our ASE Certified Technicians at Wentland Diesel Service, a full-service auto repair shop, by calling 541-938-3875 or go on-line at http://www.wentlanddiesel.com/ for more information. Our auto repair shop provides diesel fuel injection service, as well as automobile and truck repair, to the vehicle owners in  Milton-Freewater, OR, Walla Walla, WA, Pendleton, OR and surrounding areas.