Diesel Particulate Filter - DPF

The use of Diesel Particulate Filters (DPF) is a regulatory requirement in many countries. Diesel exhaust emissions standards for new cars have required fitment of a DPF in the exhaust of diesel Cars and Utes since 2009 when the 'Euro 5' standard came into force. Standards aim to deliver an 80% reduction in diesel particulate (soot) emissions, but the technology is not without its problems. There may be a need for both emission testing and to manually clean the diesel particulate filter on your vehicle.car tuning and/or 4x4 diesel tuning procedures. 

The DPF looks similar to a traditional exhaust muffler, but is mounted close to the engine. Inside is a complex honeycomb ceramic structure designed to filter the exhaust gases while minimising flow reduction. 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:

Diesel Particulate Filter active regeneration system

Active Regeneration System

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 showing that the filter is partially blocked.

passive regeneration Diesel Particulate Filter

Passive Regeneration System

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 vehicle 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. Car ECU remapping & tuning may allow for improvements in power and performance. 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.

A DPF has a design life of around 140,000 km, 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.

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

  • High km’s and compacted with fine soot.
  • Failed sensors preventing DPF regeneration.
  • Leaking injectors, valve stem oil seals, worn piston rings.
  • DPF unable to regenerate due to mainly slow short trips i.e. City running only.
  • Poor performance tuning (too rich)

There is only so many times a DPF can regenerate before the compacted soot reaches a critical saturation level at which point DPF removal or replacement is imminent. Eurotune have DPF solutions starting from just $395+GST . Call us today.