What is DPF ?
The exhaust emissions standards for new cars have effectively required fitment of a DPF in the exhaust of diesel cars since 2009 when the ‘Euro 5’ standard came into force. In fact, many cars registered before 2009 will have had one fitted too in anticipation of the change in standards.
Standards aim to deliver an 80% reduction in diesel particulate emissions but the technology’s not without problems – AA patrols are regularly called to cars with the particulate filter warning light on indicating a partial blockage of the filter.
Even if your driving isn’t mainly urban/stop-start, changes to driving style may be required to keep these systems working properly.
How do they work?
Diesel Particulate filters (DPF) or ‘traps’ do just that, they catch bits of soot in the exhaust.
As with any filter they have to be emptied regularly to maintain performance. For a DPF this process is called ‘regeneration’ – the collected soot is burnt off at high temperature to leave only a tiny ash residue.
Regeneration is either passive or active
Passive regeneration takes place automatically on motorway or fast A-road runs when the exhaust temperature is high. Because many cars don’t get this sort of use vehicle manufacturers have had to design-in ‘active’ regeneration where the engine management computer (ECU) takes control of the process.
When the soot loading in the filter reaches a set limit (about 45%) the vehicle’s ECU will initiate post combustion fuel injection to increase the exhaust temperature and trigger regeneration. If the journey is too short while the regeneration is in progress, it may not complete and the warning light will come on to show that the filter is partially blocked.
It should be possible to complete a regeneration cycle and clear the warning light by driving for 10 minutes or so at speeds greater than 40mph.
Symptoms of active regeneration
During active regeneration you may notice the following symptoms:
- Cooling fans running
- Increased idle speed
- Deactivation of automatic Stop/Start
- A slight increase in fuel consumption
- A hot, acrid smell from the exhaust.
- Engine note change
If the regeneration is unsuccessful due to an insufficient driving cycle the extra fuel injected into the cylinders will not burn and will drain into the sump. As a result, oil quality will deteriorate and the level will rise. Most DPF equipped engines will have an oil quality/viscosity sensor but it is important that you check that the oil level does not increase above the maximum level on the dipstick as diesel engines can run on their own oil if the level is excessive – often to the point of destruction.
If you ignore the DPF warning light and keep driving in a relatively slow, stop/start pattern, soot loading will continue to build up until around 75% when you can expect to see other dashboard warning lights come on too. At this point driving at speed alone will not be enough and you will need to take the car to a dealer for ‘forced’ regeneration.
Forced regeneration is required where `Active` regeneration criteria have not been met or where soot levels have increased within the DPF to a point where normal regeneration cannot be performed: typically around 70% soot loading. At this point the vehicle will enter a ‘restricted performance’ mode to prevent further damage. If left the soot loading will keep rising.
At this level of soot loading a diagnostic tool must be used to force regeneration. Above around 85% soot loading regeneration can no longer be performed on the vehicle and the DPF will need removing to be cleaned or replaced.
What can prevent normal regeneration taking place?
- Frequent short journeys where the engine does not reach normal operating temperature
- Wrong oil type – DPF equipped cars require low ash, low sulphur engine oils
- A problem with the inlet, fuel or Exhaust Gas Recirculation (EGR) system causing incomplete combustion will increase soot loading.
- A warning light on or diagnostic trouble code logged in the engine management system may prevent active or catalyst regeneration
- Low fuel level will prevent active regeneration taking place. As a general rule ¼ tank is required
- Oil counter/service interval – exceeding the service interval may prevent regeneration
- Additive tank low or empty – if the vehicle uses Eolys™ additive a low level may prevent regeneration.
If you continue to ignore warnings and soot loading keeps increasing then the car won’t run properly and the most likely outcome will be that you will have to get a new DPF costing at least £1000 plus labour and diagnostic time.
The ash residue which remains after successful regeneration cannot be removed and will eventually fill the filter. DPFs are designed to last in excess of 100,000 miles but, if the vehicle is operated correctly, many will far exceed this mileage.
The most commonly fitted type of DPF has an integrated oxidising catalytic converter and is located very close to the engine where exhaust gases will still be hot. This heat means that passive regeneration is more likely to be successful.
Some models, across a wide range of manufacturers, use a different type of DPF which relies on a fuel additive (Eolys™ fluid) containing Cerium (III) Oxide. Cerium ignites at a lower temperature and adheres to the soot particles meaning regeneration can occur at a lower temperature.
The additive is stored in a separate tank next to the fuel tank and is automatically mixed with the fuel whenever you fill up. Only very small quantities are used so a litre of additive should treat around 2800 litres of fuel – enough to cover 25,000 miles at 40mpg. It lasts about 70000 miles and is replenished during a service – at extra cost.
You will have to pay to get the additive tank refilled at some time in the car’s life – expect to pay between £150 and £200 including fluid and labour
Don’t be tempted to ignore a warning light showing that the additive tanks need refilling. It’s absolutely essential this tank is refilled as without it regeneration is unlikely to be successful and a new DPF may be needed – at significant cost. Fuel consumption can increase as a result of failed regenerations too.
Diesel Particulate Filter Cleaner
JLM Diesel Particulate Filter Cleaner solves the block problem. There is no need to dismantle the diesel particulate filter. This saves time and therefore money. Add the contents of a bottle to a full tank of fuel and drive the car again. The cleaner ensures that the soot in the diesel particulate filter burns at a low speed, when the engine is under a light load and even during short journeys.
On top of this JLM Diesel Particulate Filter Cleaner reduces the HC and CO emissions and soot emissions by no less than 20 percent. A can of cleaner could be the difference between passing and failing the MOT test. In addition, JLM Diesel Particulate Filter Cleaner ensures that fewer soot particles are deposited in the filter, meaning that the customer visits the workshop less often. JLM Diesel Particulate Filter Cleaner also conditions the engine and diesel particulate filter for a longer period of time with better performance and lower fuel consumption as a result.
Conventional cleaners contain iron to initiate the regeneration process. JLM Diesel Particulate Filter Cleaner comprises a high concentration of a patented platinum-cerium compound. The combination of platinum and cerium ensures, in the first instance, significantly improved regeneration and cleaning of the diesel particulate filter compared with conventional cleaners. The higher the concentration of platinum the better the regeneration.
Because JLM cleaners contain less iron than other manufacturers’ cleaners there is also a smaller build-up of ash in the diesel particulate filter. As a result, the service life of the filter is prolonged. Other manufacturers add more iron to the additive to achieve the same results and advantages as JLM. The result is an increase in the amount of ash in the filter, which means that the filter has to be cleaned more often and does not last as long.
For this reason, manufacturers of conventional cleaners reduce the amount of iron in the additive. This results in a drastic decrease in the regeneration performance. This is why you should use JLM Diesel Particulate Filter Cleaner. JLM Diesel Particulate Filter Cleaner restores the exhaust system and with it the fuel consumption, power and emission of exhaust gases to the original factory condition. JLM Diesel Particulate Filter Cleaner is proven to be suitable for passenger cars, commercial vehicles and heavy duty diesel retrofit systems.
Once the filter has been cleaned using Diesel Particulate Filter Cleaner it can be preventively maintained using Diesel DPF ReGen Plus 100 ml / J02200