Everything you need to know
Diesel Particulate Filters or DPF’s as they are more commonly referred too are designed to reduce emissions, caused by diesel soot, by up to 80%. Great, in theory but not so great for the end user. Vehicle manufacturers are given emissions standards which they must meet upon production of a vehicle. The European Emissions Standards were first introduced in 1970 but didn’t seriously effect the motoring world until 2008/2009 when the “Euro 5” standards were implemented.
Although DPF’s were being fitted pre 2008/2009, manufacturers were only doing this in anticipation of the Euro 5 being implemented. As mentioned, DPF’s are designed to reduce emissions by up to 80% and are the only proven method of achieving this. However, they are what they say they are on the tin – a filter. As with any filters, DPF’s become clogged. They catch or trap soot in the honeycomb filter design, therefore preventing them being released into the atmosphere. The unclogging process is what is called DPF Regeneration.
DPF Regeneration There are two different types of DPF Regeneration which are passive and active. Both however are working towards the same end result, clearing of the filter. Passive Regeneration is an automatic process where when the exhaust is at a suitable high temperature, the soot is burnt away. This usually occurs on a motorway journey or when travelling at high constant speeds such as on an A-road.
When such criteria cannot be met, and the main one being high exhaust temperature, the vehicle needs to carry out a Regeneration in another way. This way is called Active Regeneration. Most vehicles program an Active Regeneration function where the ECU (Electronic Control Unit) takes control of a Regeneration. It does this by using a functionality called “post combustion fuel injection”.
The aim of this is too increase exhaust temperatures in order to aid the Regeneration process in burning of the soot collated in the filter. For both to complete successfully there needs to be certain criteria met; Maintained high exhaust temperature Adequate amount of time to complete cycle Accurate live data from components such a DPF Pressure Sensors, Exhaust Temperature Sensors etc No faults in Engine Management system As an Active DPF Regeneration is a computer guided/initiated function, rather than the natural Passive Regeneration we mentioned, you may notice your vehicle behaving slightly differently.
Such behaviors maybe seen in the form of: Fuel consumption can increase (This can be due to the post combustion fuel injection discussed above) General sound of the engine A smell from the exhaust that is acrid and hot smelling Your RPM or Idle maybe higher than normal The engines cooling fans tend to run faster and for longer than usual For vehicles equipped with Start/Stop function, this is disabled in order for the regeneration process to be un-disturbed and also in order for post regeneration cycles to complete (Temperature to settle down to a running standard) There are several consequences to unsuccessful regeneration. Apart from leading to premature Solutions or Replacement, the aftermath can be quite expensive.
The main issue for most cars when a DPF Regeneration fails is the extra fuel injected (post combustion fuel injection) to aid the Regeneration process has to go somewhere when not used. This place is your oil sump. Not only can your vehicle end up with an extremely dangerous oil level (When too high, diesel engines can run on their own oil which results in catastrophic engine failure) but even when the oil level does not rise too high, the quality of oil is severely reduced. It becomes an oil and diesel mixture which can result in the same damage as when too high. Ignoring the DPF light and not aiding the regeneration process as a driver (motorway runs etc) will lead to your soot loading being at an increased level.
On average, when a vehicle calculates around 75% soot loading an Active or Passive Regeneration can not occur. This is when its time to visit the experts – Mobile Car Diagnostics. Also at this stage, you may be advised to have a “Forced Regeneration” Forced DPF Regeneration We see a Forced Regen as an emergency procedure to get you home, for example on the roadside in breakdown conditions. We also advise to not attempt this yourself and only let an experience Technician/Mechanic perform the procedure as this can also lead to an unpleasant situation. In extreme circumstances there is a high risk of Fire. A Forced Regeneration should be carried out using advance diagnostic equipment only.
We strongly advise against any do it you self video you may of stumbled across online. Quite often these trickery procedures are unstoppable and any of the above consequences it this article could occur. Causes of failed Regenerations and premature blocking of DPF’s As with any filter, one day they become too clogged/blocked and even a Regeneration wont help. This is the main case for a blocked DPF.
The DPF will eventually become blocked with Ash. Ash is the by-product of successful regens which eventually fills the filter and reduces its soot carrying capabilities, after all when every you burn anything (including soot) you are always left with ash. However, there are still many other causes behind a blocked DPF or a failed regeneration; For vehicle’s fitted with an additive tank, when the fluid (used to aid regeneration even at low temperatures) is too low the filter can prematurely block and/or not carry out a regen Many faults stored in your vehicles Engine Management System can disable the Regeneration function, never ignore a warning light – no many how small the fault. This can be even more frustrating if the stored fault code does not trigger any dash board warning lights. Even ignoring your Service Light can disable the process. The most popular discussed….short journeys.
As discussed above, the vehicle requires such criteria as high exhaust temperatures for a sustained period of time to perform a regeneration. Short journeys make this impossible and therefore lead to no clearing of the filter thus a blockage. A lot of vehicles require at least 1/4 of a tank of fuel in order for the ECU to recognise it can safely and successfully perform a regeneration. Keep that tank topped up!
The correct engine oil is key for any vehicle fitted with a DPF. To aid a clean regeneration process, they require low sulphur and low ash engine oil. See manufacturers recommendation. Issue’s which result in incomplete combustion increases soot loading and results it premature blocking of the filter. Aspects such as a faulty Exhaust Gas Recirculation valve (EGR Valve) or any inlet and fuel problems can dramatically increase the soot loading.
What are your options? Here at Mobile Car Diagnostics we are DPF specialist’s and offer a wide range of solutions in order to get you back on the road. Our solutions are cost effective and are carried out with the best expertise. Our highly skilled technicians are experts in their field and have the support of some of the best equipment available. We invest heavily not only in ongoing staff training but also a vast array of Main Dealer equipment in order to support our unmatched knowledge. Feel free to Contact Us here today, or if you prefer to speak to one of the experts you can reach us on 07513 637663.