What is a Diesel Particulate Filter (DPF)

A DPF is a device designed and integrated into the Diesel Engine exhaust systems to trap and remove Diesel Particulate Matter or from the exhaust gasses of the diesel engine. Much like the Catalytic Converter on conventional petrol engines, the DPF works to remove harmful toxins and lower the emissions of your diesel engine making it more environmentally friendly.

The aim is to remove 80% in the average diesel particulate (matter) emissions and although a great concept, it brings about a whole new line of problems. We are taking calls constantly from anxious customers and garages across the country when their DPF light is illuminated on the dash, indicating that there is at least a partial blockage in the DPF system.

Problems Asscoiated with DPF Systems

The DPF works to trap and remove diesel particulate matter from the exhaust gasses of the diesel engine before it exits the exhaust. This is removed into the atmosphere, simply removed from the gasses that flow through the exhaust to help lower emissions. Imagine, a DPF is like a honeycomb on the inside, similar to the Catalytic Converter (CAT) of a petrol engine. As the gasses flow through it, the DPF will trap the harmful diesel particulate matter and with it’s advanced technology break it down to remove as much of it as possible normally (between 80%-100%). The diesel particulate matter is burnt off at very high temperatures in the DPF and left behind is a very fine soot residue. The problem is this soot, it has no-where to go and so will then begin a blockage in theDPF system and this is how common DPF Problems ob5mw6r.

The soot and matter will partially block your DPF causing the DPF light to illuminate on the dash (normally when 45% blockage is reached) at which point regeneration is required to get the DPF back in to it’s safety zone. Regeneration is the DPF’s way to clear the blockage through continuously burning it at higher temperatures and allowing the now harmless produce to escape through the exhaust system. There are two types of Regeneration processes which will be explained further below.

Sometimes the DPF light will appear on the dash intermittently, this does mean there is a partial blockage in your DPF and a regeneration process is required. You should make yourself aware of this process but many people are unsure or have no idea of this DPF system as it’s still very new and not explained to everyone. If you bought your vehicle from new at a dealership, then this would have most likely been explained at the point of sale but in the second hand car trade, you can’t expect this type of information to always be passed on.

What happens is drivers see the light, then see it go off and ignore it – not knowing it’s a partially blocked DPF. They continue to drive and again it will illuminate the DPF light on the dash and go off again but eventually it will stay on permanent and in most severe cases bring on the Engine management light and even the Coil Light which could start blinking. If this happens, you will lose all power and the vehicle will fall into “Limp home Mode”. This is the automatic reaction of the Engine Management ECU and if you’re at this stage then unfortunately it will be a costly repair. This may require the DPF unit to be replaced and having the Engine Management ECU reprogrammed.

A DPF replacement will can cost between  €600 - €2000 new ( +Labour ) from main dealers, depending on the Make and Model of your vehicle.  The next time the DPF light comes on the appropriate action will have to be taken to ensure the damage is not done all over again as if you fail to act, then you could potentially void any warranty given with the new DPF unit costing you double.

What is Passive Regeneration ?

Passive regeneration is an automatic regeneration which often ob5mw6rs on drives where there is prolonged high exhaust temperatures like for example on motorway type runs, but it can’t be said that all cars get the required long journey motorway type trips necessary to complete a passive regeneration of the DPF system and so manufacturers have had to adapt the technology and designing an “active” regeneration process controlled by the Engine Management Computer also known as the Engine Control Module (ECM). 

What is Active Regeneration ?

When the diesel particulate (matter) loading in the DPF reaches a pre-set limit (normally around 50%), the ECU will make minor adjustments to the fuel injection timing system which will in turn increase the exhaust temperatures and help initiate the DPF regeneration process.  This is a smart way of getting a motorway type temperature to build up inside the DPF system and begin a full regeneration to bring the unit back to good health, however, if the journey is a bit stop/start where you’re in a built up city with traffic then the chances are the regeneration will not complete and eventually the DPF light will illuminate on the dash to tell you that the DPF system is partially blocked.

What are DPF Additivies & How They Work ?

The most common type of DPF systems feature an in-built oxidising catalytic converter, which is located close to the engine where you will find the exhaust gases will still be relatively hot so that passive regeneration is possible. In some vehicles there’s not always space nearer the engine in which case some manufacturers use a different type of DPF system, one which relies on a fuel additive to lower the ignition temperatures of the diesel particulate matter particles so that the DPF can be located further away from the engine.

The DPF additive is usually stored in a separate tank and is automatically mixed in with the fuel when you go to fill up.  Only very small amounts of the DPF additive are required for regeneration for example on average 1 litre of DPF additive would cover around 2800 litres of fuel, enough to cover 25,000 miles at 40mpg.  With this type of DPF, regeneration would be initiated by the ECU roughly every 300 or so miles depending on the vehicle and will normally take 5-10 minutes to complete. Normally you won’t even notice this process taking place and if anything, once regeneration is completed you might see a glimpse of white smoke exit the exhaust and that’s it.

If you would like to understand more about regarding DPFs Please find an excellent explanation of the function of a DPF and how they are Not suitable for everyone taken from the AA Uk Website Click Here

What is a EGR Valve ?

If you any questions or would to find out more please Click Here to contact us. 

We can provide DPF and EGR Removal or Replacement services for all of these vehicles and Many More