DPF stands for diesel particulate filter. The filters are employed to minimize the number of hazardous particulates that escape the exhaust systems of diesel cars. The intention is to make the air cleaner and safer, particularly in tight spaces. EHC Teknik produces DPF filters for various applications, and we’re more than happy to answer any questions that you have regarding this technology. Learn more about it here.

Euro 5 standards

Since 2009, when the “Euro 5′ standard took effective, exhaust emission standards for all new diesel vehicles have effectively required the fitment of the DPF into the exhaust system. Actually, many vehicles which were built before 2009 will come with the filter in place.

The measures are well-intentioned, as the diesel particulate (soot) emissions can cause severe health issues for humans. DPFs lower the emission of diesel smoke by 80percent, but they’re not suitable for everyone. Even if you drive not mainly urban/stop-start, changes to driving style may be required in order to keep these systems operating effectively.

What is the process by which diesel particulate filters work?

Diesel Particulate Filters (DPF) capture the soot particles that are preventing them from being emitted into in the system of exhaust. Like any filter one must be cleaned frequently to ensure their performance. For a DPF this process is called ‘regeneration’. In this process, the collected soot is burnt off with high temperatures so that there is only the ash.

Regeneration can be passive or active

Passive regeneration

  • Passive regeneration is a process that occurs automatically on motorways when the temperature of exhaust is high. Since many cars aren’t frequently driven on motorways frequently, car manufacturers have come up with “active” regeneration. In this case, engines management computers (ECU) takes control of the process.

Active regeneration

  • If the filter is filled with soot up to a set limit (about 45%) your vehicle’s ECU will start post-combustion fuel injection to increase the exhaust temperature and initiate regeneration. If the engine is switched off while regeneration is in progress, it may not be completed and the warning indicator will come on to indicate that the filter is not fully blocked.

It should be possible to complete a regeneration cycle and then clear the warning light through driving and raising the temperature as a result.

Symptoms of active regeneration

  • In active regeneration, you may experience the following symptoms:
  • Cooling fans on
  • Increased idle speed
  • The automatic Stop/Start feature is disabled.
  • A slight increase in the fuel consumption
  • A spicy, pungent smell emanating from the exhaust.
  • Change to the engine note

If the regeneration fails because of a lack of motor cycle, any extra fuel injected into the cylinders won’t ignite and flow out to the sump. Therefore, the quality of the oil will decline and the level of oil will rise. Most DPF-equipped engines will have an oil quality/viscosity indicator, but it is imperative to verify that the oil’s level doesn’t exceed the maximum level on the dipstick since diesel engines can run on their own oil if the level is high, usually to the point of destruction.

If you ignore the warning and continue to drive at a moderately slow stop/start pattern, soot will continue to build up until the level is around 75%. When you can expect to see additional dashboard warning lights come on. At this point driving at a fast pace will not suffice to remove the filter. You’ll have to take your car to a repair shop to get “forced” regeneration.

Forced regeneration

Forced regeneration is needed when “active” regeneration criteria have not been met and soot levels within the dpf have increased by about 70%. If left the soot loading will continue to increase. At this point the diagnostic tool should be employed to force regeneration. Around 85% of soot load, regeneration can no longer be carried out on the vehicle . In this case, you will need to get rid of your DPF to be replaced or cleaned.