Common Misconceptions


DPF removal. We are seeing lots of consumers getting recommendations to remove their DPFs as they are “problematic”, “expensive” and many other reasons. There are lots of companies offering this service by way of physical removal and a software edit to allow the cars computer to continue to function blind and unaware


This always causes problems of varying degrees, from reduced injector life, to constant smoke, the list is extensive. Aside from the fact that it is illegal and an MOT failure and you are polluting the environment.


When a few lines of computer code are altered amongst a complex web of 2-3 million interweaved commands it will have a detrimental effect. The companies and individuals performing these ‘deletes’ do not need any technical knowledge of how the system works. The kits for performing the software edits are readily available to anybody with a computer. Unfortunately they are advising people posing as experts.


DPFs are actually quite reliable. They are a self regenerating system that relies on the correct function of other components to complete their cycle.


If your DPF light is coming on it is a good early warning sign that something else is wrong. If the engine management system is working correctly your DPF will take care of itself. Don’t be convinced you are saving money by removing it, the saving is short term and you will still have the same fault that blocked it in the first place which is also making your engine run inefficiently. It will almost definitely be down on power and using more fuel because it is just turning diesel into soot which is why the DPF cannot clean itself. The faults causing this WILL get worse not better so removing the symptom (DPF) will not fix the fault. Likewise just replacing a blocked DPF with a new one will not fix the reason the original blocked in the first place. We often find owners who have just had a blocked DPF replaced will be facing the same situation a few months later. We generally find once the cause has been rectified a blocked DPF will clean itself in a few miles and does not need to be replaced. Worst case normally involves physically removing the accumulated ash from the DPF if the car has been driven for too long with a fault.


So for a blocked DPF you need to look at why your fuel is not being burnt efficiently and this will take some expertise as it is not always straight forward but I am sure you can see the logic here.


The Bottom Line      


Lawgistics have kindly provided the legalities of the matter as we believe it is important people are presented with the facts.                                       


An investigation has found that thousands of UK drivers are illegally driving modified cars without diesel exhaust filters. Diesel exhaust filters can become clogged and likely to malfunction and break because they process large amounts of particulate matter. To replace a broken filter can cost over £1000, so to avoid this some drivers have opted to have the filter removed or have been advised to have it removed as a solution to persistent problems. 


The procedure to remove the filter is legal but driving the car without it is illegal and any vehicle found with a modified filter will be subject to a fine of £1,000 for a car or £2,500 for a van.


Current emissions tests are unreliable for detecting the presence of the filter, which is one reason drivers are be tempted to do it. Current MOTs have been described by some commentators as unfit for purpose as they only require a visual test of the outside of the DPF to see if the filter is functional.

However, from May 2018 the DVSA plans to introduce changes to emission tests that will improve their ability to detect filters that have been tampered with.  The DVSA Chief Executive Gareth Llewellyn is quoted as saying:  “Vehicles found to have tampered with or missing DPF filters will fail their MOT...the DVSA continues to pursue such offences and will take action against any MOT garages found to be conducting illegal modifications.”  In September 2017 two mechanics from Sheffield were banned form MOT testing for two years for carrying out DPF removal and advertising the service, as the practice brings the MOT scheme into disrepute. 


Over 1800 diesel cars from 2014 to end of 2017 in the UK have been found by the DVSA to be on the road without the legally required diesel particulate filters and without action the figure is likely to rise as consumers and those in the trade view it as a potential solution to issues. However, the pollution produced by the particulate matter in the diesel fumes can be damaging to the heart and lungs as well as unborn children in the womb. Noxious fumes created by diesel engines have been linked by The World Health Organisation to 38,000 premature deaths every year. 


DPF removal is not a remedy or a repair in accordance with the Consumer Rights Act 2015 and we don’t advise it is offered as such under any circumstances.  


DPF deletion will not fix the fault that caused it to block in the first place.




Another good example is EGR removal/deletion. The EGR or Exhaust Gas Recirculation’s main function is to reduce oxides of nitrogen which is a greenhouse gas, by bleeding oxygen depleted exhaust back in with the fresh air under certain engine conditions.


This does come with a drawback. Exhaust contains soot, and if your engine is not burning its fuel efficiently it can soot up your intake. Again one component being blamed for another failure.


What lots of people don’t realise is two things. Firstly the exhaust gas increases the combustion temperature at idle and light load, this improves combustion efficiency and increases the life of injectors and DPF’s to name just two. Secondly modern systems pump exhaust gas flow through a heat exchanger. Modern engines are very thermally efficient, so much so that they struggle to heat the water to running temperature in cold weather. The heat exchanger takes heat from your EGR and heats the water, often directly into the cabin heater to warm you quicker on a cold day. Blanking the EGR stops both of these things happening.




If you have had an MOT failure due to DPF removal all is not lost. We can reinstall your original software and fit a new DPF. In most cases the reason the DPF was removed will still need to be found, luckily you are in good hands.

 

Diesel Particulate Filters (DPF)