DPF: what is the particulate filter and what is it for?

The fight against CO2 emissions has hit diesel engines hard, but manufacturers have managed to make these engines less polluting thanks to the adoption of the particulate filter.

The abbreviation DPF is the acronym for Diesel Particulate Filter and this is a device fitted on all new-generation diesel cars from category Euro 4 onwards. Thanks to the DPF, there’s a significant reduction of all PM10 particles coming off the exhaust by consequently decreasing polluting emissions released into the atmosphere.

Inside the DPF there’s a silicon carbide filter equipped with channels and alveolar cells that filter and retain the particulate matter. To help the filtering process, the filter uses a cerine-based additive that causes the aggregation of the particles into larger agglomerations so they can be more easily filterable.

DPF regeneration: what it is and what it is used for

To keep the particulate filter efficient, it is essential that it carries out and completes the “DPF regeneration”, an automatic process that takes place thanks to the self-diagnosis of the filtration system and various pressure sensors situated before and after the filter. Depending on the pressure differential and the calculated percentage of soot in the filter, the system starts the regeneration.

The duration of the operation is about 5 or 10 minutes and during this period it is advisable to keep the RPMs constantly at or over the 2500mark, until the regeneration is completed.

After a certain number of regenerations the vehicle will signal the need of topping up the level of additive present in the filter. In some cars the filters are designed and produced to operate without the use of additives. This is a pro because they require less maintenance but also a con because the additive helps reaching higher temperature faster and make it easier to complete a regeneration in less time.

DPF cleaning: why it’s important

The DPF also uses further combustion, thanks to the help of extra diesel injections, to reach higher temperatures quickly. Such high temperatures allow the particles to be transformed into smaller and less polluting particles that are subsequently expelled together with the other exhaust gases. The extra combustion causes the fuel in excess to slide through the piston rings into the oil sump, slowly degrading the engine oil. For this reason, it is very important to complete the regenerations once started otherwise the system will need more regeneration attempts, degrading the oil at an higher rate.

How much does it cost to clean or replace a particulate filter?

If the regeneration does not take place, the DPF becomes clogged causing a loss of performance and an increase in consumption. As mentioned in the previous paragraph, frequent regeneration attempts lead to a dilution of the engine oil, which then needs to be replaced more frequently.

Keeping the particulate filter in perfect working order is critical to avoid mechanical issues and to avoid having to deal with huge cleaning or replacement expenses.

On average, a DIY cleaning kit has a price of about $1500, while the replacement of the DPF can cost up to $8,000-10,000 for the most expensive devices.

Click here to find the best diesel mechanics in Adelaide

 DPF delete

The particulate filter is removed off the car, the interior parts of the filter are removed and the filter is refitted to the vehicle. In some instances, the filter is removed and replaced with a section of the exhaust system without the filter (straight pipe). The technician proceeds then working on the vehicle control unit software, deactivating the regenerations and the various sensors that monitor the level of blockage of the filter.

This procedure not only resolves all the issues mentioned before, it also slightly improves the performance of the vehicle (thanks to the reduced back pressure) and it improves the fuel economy. It also saves maintenance costs to the driver as the vehicle won’t need regular DPF fluid top ups anymore.

Is DPF delete legal in Australia?

No, it is illegal to remove the DPF or any other component of the exhaust system in Australia. If the modification increases the emissions value of the vehicle it can only be used with an ADR exemption or for racing purposes and the standard on-road use would be strictly forbidden. This will also void the vehicle warranty and the insurance policy.

Click here to find the best mechanics for DPF delete in Adelaide