DPF Filter Delete/RemovalThe 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 (soot) emissions but as owners are finding out with great expense, the technology is not without its problems.


The DPF looks similar to a traditional exhaust silencer, but is mounted close to the engine. Inside is a complex honeycomb ceramic structure designed to filter the exhaust gases while minimising flow reduction (which would otherwise limit performance). By forcing the exhaust gases through the walls between the channels of the DPF, the particulate matter is deposited on the walls, so reducing the amount of air pollution. Once the DPF reaches a certain level of ‘Saturation’ it performs a regeneration cycle to burn off the particulate matter inside the filter.

There are two types of regeneration:

  • Active DPF Regeneration Removal
  • Passive DPF Renegeration Removal


When the soot loading in the filter reaches a set limit (about 45%) the ECU will initiate post combustion fuel injection to increase the exhaust temperature and trigger regeneration. If the journey is a bit stop/start or you take your foot off the accelerator 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.


Passive regeneration takes place automatically on motorway-type runs when the exhaust temperature is high. Because many cars don’t get this sort of use car manufacturers have to design-in ‘active’ regeneration where the engine management computer (ECU) takes control of the process.

A car which is primarily used for motorway use will generally run at warmer temperatures and therefore produce far less particulate matter than one used in a stop/start city environment. A vehicle used on the motorway is also going to be able to regenerate more often and effectively as it is in the perfect driving environment for the regeneration process to occur.

The operation of the DPF is controlled by the ECU and requires multiple signal feeds from various sensors in order to operate effectively. The most common type of DPF runs two pressure sensors and a varying number of temperature sensors. There is differential pressure sensor mounted in the engine bay which picks up the pressure both before and after the DPF. It is the variance in pressure between these two pick-ups which allows the ECU to calculate the percentage saturation of the DPF. Once the ECU establishes the saturation level it is able to force a regeneration cycle. The progress of the cycle is monitored by the temperature sensors and takes constant feedback from the differential pressure sensor which enables to know when the burn off process is complete.


Some manufacturers use additives to reduce the ignition point of the soot particles by secreting small amounts of fluid into the fuel tank which mixes with the fuel. The additive is a service item and is designed to require refilling every 75,000 miles approximately. Ignoring the warning for low additive will mean the DPF will not regenerate properly and will almost certainly require a new DPF. Certain models of vehicles however require the DPF to be changed with the additive top up which makes for expensive servicing bills.


A DPF has a design life of around 75,000 miles but this can be subject to large variation depending on vehicle use and engine condition. Every time the ECU forces a regeneration cycle it burns the particulate matter down to a much smaller amount of finer soot, they don’t get completely removed from the filter. Over time, the fine soot content builds up to a point where a regeneration cycle is no longer able to be performed; at this point the filter either needs emptying or replacing.

Removing the DPF is often advised to check the opacity of the exhaust emissions which can give some indication of any potential running issues which can impact on the operation of the DPF. Issues such as leaking injectors and engines burning oil can massively reduce the life of a DPF.


There are a multitude of reasons a DPF can fail, the most common are highlighted below:

  • High mileage and compacted with fine soot.
  • Failed sensors preventing DPF regeneration.
  • Lack of additive in fuel (where fitted) causing incomplete burn off.
  • Engine issues i.e. leaking injector, valve stem oil seals, worn piston rings.
  • DPF unable to regenerate due to driving conditions i.e. City centre.
  • Poor performance tuning.
  • Driving in too low of a gear on a motorway disallowing the regeneration to commence.

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  • Are you having problems with your DPF?
  • Are you facing a large bill for your DPF replacement?
  • Is your DPF causing you poor fuel economy?

DPF Removal can solve your problems
Ribble Valley Diesels is an authorised Celtic Tuning dealer. Celtic Tuning are genuine software developers and as such have unrivalled knowledge and experience in DPF Removal from modern ECU’s. Our DPF delete software will ensure that you have trouble free motoring after the DPF removal and give you piece of mind that your vehicle will not go into limp mode due to DPF regeneration ever again.

Modern turbo diesel management systems all accommodate the use of a ‘diesel particulate filter’ as it has become mandatory as part of Euro Emission controls. The problem many are finding is that any driving other than motorway use will cause the DPF to clog up and force it to regenerate. There is only so many times a DPF can regenerate before the compacted soot reaches a critical saturation level at which point DPF replacement is imminent. With the DPF not being part of an MOT emission test it is not a requirement for it to ‘function’ as a DPF. Our DPF remap in basic switches off the functionality of the DPF ensuring it never attempts to regenerate again. What is required is that the DPF filter is removed from the centre of the exhaust core ensuring all sensors are still in place and functioning. When finished, the DPF still looks to be in situ with all sensors operational just not DPF trap and no regeneration problems.


DynoIT - VO06UMVCeltic Tuning’s DPF Removal software will ensure that your vehicle operates without the DPF being present. Most customers also benefit by having a performance remap alongside the DPF remap which provides even better gains than just the DPF Removal itself. The benefits of DPF removal are as follows:

  • No expensive DPF replacement costs.
  • No more limp modes when the vehicle decides to do a forced regeneration.
  • Improved MPG due to the removal of an air restriction allowing the engine to breather better.
  • Improved power output of the vehicle. We have tested many vehicle’s on our dynamometer before and after DPF removal and every single one has provided a performance gain. An example of one is the Fiat 500 1.3 Multijet 75bhp which gained 8bhp and 10lbft after having DPF removal.
  • After DPF removal it is possible to use bio fuels as they can no longer cause issue to the DPF filter.


It is not illegal to remove a DPF filter form your vehicle. It is an offence under the Road vehicles (Construct ion and Use) Regulations (Regulation 61a(3)) 1 to use a vehicle which has been modified in such a way that it no longer complies with the air pollutant emissions standards it was designed to meet. Removal of a DPF will almost invariably contravene these requirements.

From February 2014 the inspection of the exhaust system carried out during the MoT test will include a visual check for the presence of a DPF. A missing DPF, where one was fitted when the vehicle was built, will result in an MoT failure.

Therefore, by fitting a bypass pipe you will find that your vehicle fails an MOT test. Other methods such as removing the internal filter will be visually standard and will enable you to reinstall a filter a future date should you wish to. Please note this is not to say this will not fail an MOT by completing this.


Celtic Tuning have an extensive reseller network which covers 16 different countries and over 80 outlets. Our expertise covers all aspect of engine related works from DPF Removal, EGR Removal, Economy tuning, Performance Tuning right through to full custom conversions on high performance engines. If you feel that this could be of benefit to your business then please get in contact, a DPF Remap could add an additional arm to your business generating you additional income.