Particulate filters are an integral component of any 4x4 vehicle that runs on a diesel engine. This is because particulate filters are designed to trap and eliminate the soot that would have otherwise been released into the environment from a vehicle exhaust system.

Thus, the effectiveness (or lack thereof) with which particulate filters work will often determines whether an automobile owner complies with environmental protection laws formulated to deter air pollution from vehicle emissions.

Here are answers to three questions that a first-time 4WD vehicle owner may have about diesel particulate filters.

How Do Particulate Filters Work? 

Diesel particulate filters work through the process of regeneration. Through this process, particles of soot that may have accumulated on the filters are burnt off at high temperatures. Exposure of soot particles to the high temperatures turns these particles into a residual ash-like compound, thereby allowing the regeneration cycle to continue.

Particulate filters used with diesel engines are named after their mode of regeneration. This nomenclature gives rise to active regeneration filters and passive regeneration diesel particulate filters.

What Differences Are There Between The Two Types Of Filters?

Active regeneration filters work by bringing increasing heat energy levels within the filter such that the temperature inside the filter is higher than the temperature required to burn particles of soot. The additional heat energy needed in an active regeneration filter has its source in the heat energy given off by the burning soot particles.

In a passive regeneration diesel particulate filter, a catalyst is introduced into the filters. The catalyst is responsible for bringing down the ignition temperature of accumulated soot particles. Once the ignition temperature goes below the temperature of exhaust gases being produced, the regeneration process commences.

In a large number of cases, there's also a significant difference between the cost of an active regeneration filter and its passive counterpart. This is because active filters are designed with a higher degree of complexity. As a result, the installation of active regeneration filters is also often more complicated than the installation of passive filters. DIY-minded 4WD vehicle owners would have better luck with a passive regeneration filter.

How Does One Know The Type Of Filter Fitted On Their 4WD?

Passive regeneration diesel particulate filters are sensitive to the sulfur-content in diesel fuel. Thus, this type of filter will often only be fitted on 4WD vehicle engines that operate on ultra-low sulphur diesel only.