Particulate Particulars

Service & Repair Brooke Wisdom March 5, 2011

With scheduled cleanings and a little care, a diesel particulate filter should enjoy a long service life.

Diesel Particulate Filters (DPFs) hardly enjoy an easy ride. The can-shaped addition to exhaust systems — needed to meet 2007 emission standards — faces an ongoing attack in the form of high temperatures, pressures, vibrations and corrosive chemicals. In the face of all that, they are expected to capture soot, reduce everything to a fine ash and hold the remains until it is time for a cleaning.

But decisions and steps in the shop can help determine whether the filter will make it from one scheduled cleaning to the next.

The choice of engine oil certainly can make a difference. “Most OEs have designed the aftertreatment systems for exclusive use with CJ-4 oil,” notes Matthew Leustek, a Caterpillar on-highway engine core technology and systems engineer, referring to the low-ash formulas that were made possible with the widespread introduction of Ultra Low Sulfur Diesel (ULSD).

“Not using CJ-4 will lead to measurably worse fuel economy over time due to higher ash accumulation rates, potentially lead to DPF failures, potentially lead to low-power complaints [because of elevated back pressure], and may lead to the inability to effectively ‘ash service’ the DPF in extreme cases.” It will be difficult to measure the change in fuel economy from month to month, but a trend will emerge over a year, he says.

Granted, a typical build-up of ash should be largely unnoticed by drivers, notes Ed Saxman, product marketing manager for Volvo Trucks North America. “In reality, both the inlet air filter and the DPF are large enough that, with proper maintenance, there is not a significant difference between a new filter and a dirty filter.”

A DPF usually will arrive in a shop when it is time to address its increasing load of ash. That is when teams will need to decide whether to clean the equipment themselves, or participate in an exchange program offered by an OEM.

While the cleaning process largely uses a controlled shot of air, it involves more than reaching for the hose attached to the shop compressor.

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