DPF

Diesel particulate filters (DPF) are devices that physically capture diesel particulates to prevent their release to the atmosphere. Diesel particulate filter materials have been developed that show impressive filtration efficiencies, in excess of 90%, as well as good mechanical and thermal durability. Diesel particulate filters have become the most effective technology for the control of diesel particulate emissions—including particle mass and numbers—with high efficiency.

Diesel particulate filters can quickly accumulate considerable volumes of soot. Several liters of soot per day may be collected from an older generation heavy-duty truck or bus engine. The collected particulates would eventually cause excessively high exhaust gas pressure drop in the filter, which would negatively affect the engine operation.

Therefore, diesel particulate filter systems have to provide a way of removing particulates from the filter to restore its soot collection capacity. This removal of particulates, known as the filter regeneration, can be performed either continuously, during regular operation of the filter, or periodically, after a pre-determined quantity of soot has been accumulated. In either case, the regeneration of filter systems should be “invisible” to the vehicle driver/operator and should be performed without his intervention. Thermal regeneration of diesel particulate filters is typically employed, where the collected particulates are oxidized—by oxygen and/or nitrogen dioxide—to gaseous products, primarily to carbon dioxide.

Disadvantages of DPF

The Diesel Particulate Filter reduces engine power because of the restriction in the exhaust caused by the filter. The cylinders have to work more to expel the exhaust gases (the so-called pumping work) and therefore the net power that goes to the wheels is reduced. The power loss is higher as the load and rpm increase.
Reduced fuel economy, because of lower engine performance and wasted fuel used in regeneration of the filter.
Increased wear and tear caused by soot backing up into the turbo and Exhaust Gas Recirculation (EGR) and diesel in the oil. During re-gen fuel is injected into the engine during the exhaust stroke. Small amounts of this fuel leaks past the piston and into the engine oil, thus dilutes the oil, which reduces the oil's ability to lubricate the engine properly, causing extra wear and reduced engine life.
DPF is very expensive to change, in the region of 1000£ and to clean 300£ (and more frequent cleaning afterwards). Useful life of a DPF ranges between 80k and 125k miles, depending on the vehicle usage.

From February 2014 the inspection of the exhaust system carried out during the MoT test will include a check for the presence of a DPF. A missing DPF, where one was fitted when the vehicle was built, will result in an MoT failure. A vehicle might still pass the MoT visible smoke emissions test, which is primarily intended to identify vehicles that are in a very poor state of repair, whilst emitting illegal and harmful levels of fine exhaust particulate. It is an offence under the Road vehicles (Construction and Use) Regulations (Regulation 61a(3))1 to use a vehicle which has been modified in such a way that it no longer complies with the air pollutant emissions standards it was designed to meet. Removal of a DPF will almost invariably contravene these requirements, making the vehicle illegal for road use. The potential penalties for failing to comply are fines of up to £1,000 for a car or £2,500 for a light goods vehicle.

DPF

Disadvantages of DPF

Reduced fuel economy, because of lower engine performance and wasted fuel used in regeneration of the filter.

DPF is very expensive to change, in the region of 1000£ and to clean 300£ (and more frequent cleaning afterwards). Useful life of a DPF ranges between 80k and 125k miles, depending on the vehicle usage.

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