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Diesel Particulate Filter (DPF): What You Need to Know

People who own diesel cars, definitely have diesel particulate filters. However, most people lack the slightest clue on how to maintain the particulate diesel filter in their vehicle which results in the filters clogging with soot.

For two decades now, we have been fitting diesel particulate filters in diesel fuel vehicles. Nonetheless, if tampered or lack superior maintenance your vehicle ends up with serious consequences.

Diesel particulate filter as the name filter suggests trap or ‘filter’ particles. The particles are diesel exhausts soot particles and therefore you have to empty occasionally to maintain good performance in your vehicle.

The DPF (Diesel Particulate Filter) requires cleaning regularly, by a process referred to as regeneration. The process is either active, forced regeneration or passive.

In this article, we will explain exactly all what you need to know about diesel particulate filter and ways of maintaining it.

What is a diesel particulate filter (DPF)?

DPF (Diesel particulate filter) is a trap or rather a filter just like the name filter
DPF captures and stores exhaust soot or soot traps from your vehicle.
Credit: rac.co.uk

Diesel particulate filter is a trap or rather a filter just like the name filter, that captures and stores exhaust soot or soot traps from your vehicle with the aim of reducing emissions from diesel vehicles.

However, because the soot trapped is infinite capacity, you need to empty it periodically in order to avoid blockage and regenerate the diesel particulate filter (DPF).

The regeneration process burns off the trapped soot which is deposited in the vehicles filter reducing harmful exhausts emissions to the environment.

This also prevents the release of the tell-tale black smoke which we used to see many years ago from diesel cars especially when the vehicle was accelerating.

At high temperatures, the accumulated soot is burnt off around 600degrees Celsius leaving only ash residue which effectively regenerates or renews the filter ready filter more particles. From the vehicle.

In simple terms, diesel car owners refer to the regeneration process as of taking soot pollution from the car’s engine and storing it ready to get rid of it. That is the reason why you have to clear the soot occasionally.

The diesel emission re harmful to our health and to the environment at large. The good news came in the year 2009 when the Euro 5 Exhaust emission legislation was introduced to help lower vehicles CO2 emissions and effectively made diesel particulate filters a must have for any diesel car.

Since then, the diesel particulate filters are fitted in all diesel cars or one in every two cars a year are diesel powered.

After all, the measures put in place to have the safety filter. As we can call it has shown incredible results. There is no emission of the harmful back smoke.

What causes a diesel particulate filter (DPF) blockage?

Every vehicle and car engine combination have different reasons as to why the filter can block. They can be caused by reasons like the rate at which the car is releasing the soot, oil quality, driving style, fuel quality and the location of the particulate filter (DPF).

All the above reasons one or another, causes diesel vehicles filters to block and fail to regenerate fully.

Generally, most problems arise with vehicles that are doing town rounds since the regeneration process is not happening as it should.

In this case, a diesel vehicle driver should be on the lookout for a message or an illuminating light that shows the diesel particulate filter (DPF) is not functioned as per the requirements.

The message is a warning that if you continue to drive in the same manner, the soot accumulates and the vehicle goes into a limp mode where even driving in speed is restricted.

This buildup of the soot where the vehicle accelerating speed has been filtered requires the mechanic help to carry out a forced regeneration on the vehicles filter.

The breakdown of what causes filter particulate blockage:

  • Frequent small journeys where the diesel vehicles engine fails to get hot.
  • Wrong and poor quality engine oil.
  • When the fuel level is low. Generally, when the oil is less than a quarter active regeneration fails to take place.
  • If your car uses Eolys addictive. Low levels of oil in the tank prevent regeneration.
  • Problem with vehicles fuel system resulting in excessive soot.

How do you maintain your vehicles diesel particulate filter (DPF)?

When extra fuel is automatically injected it means there is an active regeneration as part of the cars ECU.

Maintaining a good diesel particulate filter (DPF) is to ensure that your vehicle is able to fully regenerate by itself when the filter has soot, or when the diesel particulate filter (DPF) warning light pops up.

  • Always ensure that you use low ash oil for the engine. Failure to use the specified engine oil for your vehicle ultimately results in the soot build up.
  • Avoid short journeys if your vehicle is the diesel engine. We hardly use our cars the same way. However, small or short trips with a diesel engine vehicle will make the car owner experience soot build up as the regeneration process is not taking place fully as it is required.
  • 100% Biofuel diesel. Biofuel diesel contributes to the formation of more soot and builds up at the filter. The bio-oil does not burn fully and produces more particles as required with regular cars.

We have two types of regeneration:

  • Active regeneration
  • Passive regeneration

Active regeneration

When extra fuel is automatically injected it means there is an active regeneration as part of the cars ECU. This is where the filter will reach a predetermined unit mostly at 45% and raises the temperature of the exhausts burning off the trapped and stored soot.

Problems arise when the vehicle’s journey is short as the process of regeneration fails to go a full cycle.

If this happens where the soot blocks the filter, look out for a warning light on the dashboard. This now means that it is time to visit a mechanic who carries the forced regeneration.

However, if you continue driving for around ten minutes at a speed higher than 50mph, the warning light clears which means the filter is also minimizing the blockage.

Symptoms to look out for and know if the vehicle is having active regeneration:

  • Engine note changes.
  • Fuel consumption slight increase.
  • Idle speed increases.
  • Acidic, the hot smell coming from the exhaust.
  • The cooling fans are running.
  • Automatic deactivation of the start and stop.

Passive regeneration

Passive regeneration happens when the vehicle is running at a speed on the long motorway journeys. Which enables the exhaust temperatures to increase to high levels and completely burn off the buildup soot which is at the filter.

We recommend diesel car owners to regularly give their vehicles a considerable 30-50 minutes of a sustained quality speed on the motorway to help and clear the filter.

However, most drivers hardly take this kind of driving. That is why manufacturers designed an alternative kind of regeneration.

What do I do if both active and passive regeneration fail to work?

If your vehicle is not having passive or active regeneration, then a warning light comes up to show that the soot had completely blocked the filter.

This is the time to have your vehicle checked out. If the warning light stays on, it turns to red still additional DPF lights pop up. It is advisable not to ignore these signs as they may result in the vehicle getting expensive damages.

This is where forced regeneration now comes to play.

Forced regeneration is definitely expensive as you have to carry the process in the workshop with the help of a mechanic.

Forced regeneration is the process of removing excess or build up soot in this case in the garage to automatically make the vehicle regenerate again by itself.

Failure to have forced regeneration happening, the vehicle develops limp mode as the filter is clogged and it is not emitting smoke. Some vehicle models will work well after being subjected to a moderate speed of 50 mph.

Do I require diesel particulate filters to pass through the MOT?

Yes. Reason? In any case, if you remove the filter, the vehicle fails its MOT. Since 2004, diesel particulate filter has always been part and parcel of the MOT tests.

Removing diesel particulate filter causes the warning lights to show. This is simple terms is MOT point of failure. The warning lights on the dashboard should always remain during the vehicle test.

The Bottom Line

Generally, diesel produces a lot of soot. Which is in particulate matter that can cause health problems like respiratory problems and cardiovascular diseases.

Since 2009, modern diesel vehicles are fitted with diesel particulate filters in their exhaust so as to stop the soot from passing through to the atmosphere and causing environmental problems.

This aim cut over 80% of the particle emissions from diesel vehicles.

Important notes

To avoid all the issues that result with clogged exhaust here are five points to consider you are trouble free.

  • Drive faster
  • Always have the EGR valve checked frequently.
  • Use the right engine oil.
  • Drive for long distance and keep out of cities and towns
  • Lastly, buy the right engine vehicle.

Okay, now you have all the information you need to know. Keep the diesel particulate filter on your vehicle in good shape.

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Tim MillerFounderOBD Advisor

I’m Tim Miller from Denver, Colorado. I’m the founder of obdadvisor.com, an automotive blog about "Diagnostic Tools and Auto Repair". My fan page is facebook.com/autozikcom. I've been working as an automotive mechanic and blogger for over 10 years writing articles to share my experiences and expertise.

Web: https://www.obdadvisor.comEmail: [email protected]
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