DPF stands for diesel particulate filter. The filters are employed to reduce the number of harmful particulates that escape the engines of diesel vehicles. Keep reading to learn more.
Euro 5 standards
Since 2009 when the “Euro 5′ standard came into the market, exhaust emissions standards for diesel vehicles of the new generation have mandated the installation of the DPF in the exhaust systems. In reality, most cars registered before 2009 will have a filter fitted as well.
And these measures are taken for good reason since diesel particulate (soot) emissions cause serious health problems in humans. DPFs cut down on diesel soot emissions by 80%, but they aren’t suitable for all. Even if you’re driving not mostly urban/stop-start, some changes to your driving routine may be required in order to keep these systems operating effectively.
What is the process by which diesel particulate filters function?
Diesel Particulate Filters (DPF) collect the soot particles that are preventing them from exiting the system of exhaust. Like any filter, it is essential to empty them frequently to ensure their performance. For DPFs, DPF this is known as ‘regeneration’. Through this process, the soot that is collected is burned high temperatures to leave only ash.
Regeneration can be passive or active
Passive regeneration
The process of passive regeneration occurs automatically on the motorway if the exhaust temperature is high. As many cars are not driven on the motorway very often, the manufacturers of cars have designed “active” regeneration. In this case, the engine management computer (ECU) manages the process.
Active regeneration
When the filter is clogged with soot, it will reach a set limit (about 45%) in the case of a vehicle, the ECU will initiate post-combustion fuel injection to raise the temperature of the exhaust and initiate regeneration. If the engine is turned off while regeneration is underway, it could not be completed, and the warning light comes out to indicate that the filter is partially blocked.
It should be possible to complete the cycle of regeneration and then clear the warning light by driving and then increasing the temperature that way.
Symptoms of active regeneration
In active regeneration, you may be able to observe the following signs:
- Cooling fans are running
- Increased idle speed
- Deactivation of automatic Stop/Start
- A small increase in the amount of fuel consumed
- A hot, acrid smell from the exhaust.
- Engine note changes
If the regeneration fails because of an insufficient drive cycle, the extra fuel injected into the cylinders will not ignite and flow out into the sump. Therefore, the quality of the oil is deteriorating and the oil level will rise. The majority of DPF-equipped engines have an oil quality/viscosity monitor, however, it’s important to check that the oil level isn’t higher than what is the maximum value on the dipstick, as diesel engines are able to run with their own oil when the level is too high – frequently to the point of destruction.
If you do not pay attention to the warning light and keep driving with a comparatively slow stopping and starting, the soot will continue to build up until around 75% when it is possible to expect additional dashboard warning lights to come on. At this point, driving at speed alone will not be enough to clear the filter and you will need to take the car to a dealership to undergo “forced” regeneration.
Forced regeneration
Forced regeneration is needed when “active” regeneration criteria have not been met and the soot levels within the DPF are now at around 70%. If not addressed, the loading of soot will continue. At this level, it is necessary to use a diagnostic tool be used to initiate regeneration. If you are at around 85% soot load, regeneration can no longer be carried out on the vehicle. You must remove all dpf parts and have them cleaned or replaced.
