WHAT IS THE DPF SYSTEM?
Since the Introduction of ‘Euro 5’ standards in 2009, emissions requirements for new diesel vehicles require Particulate Filters to be fitted to the exhaust from the factory. Even before this change of regulations, many vehicle manufacturers where already fitting DPFs in anticipation of the new regulations. The ‘Euro 5’ and future standards aim to deliver reductions in soot output (diesel particulates) of up to 80%! Sounds brilliant, but these filtration systems are not free from issues causing DPF warning lights, engine limp home mode, reduced efficiency/mpg and poor engine performance.
Regeneration of the DPF is required for efficient operation of the filter and engine, this can happen passively (while driving under normal conditions) or actively (while driving or also a “forced” regeneration). The filter will passively regenerate when under normal driving conditions that allow it to reach a high enough temperature to burn off the deposits in the filter, this could be for example on the motorway. An active regeneration process is completed by the ECU causing an increased temperature of the exhaust gases passing through the filter, which then allows burning away the carbon deposits. To control this process a sensor transmits data to the engine control unit that then calculates the increase in post-injection fuel quantity required to increase the temperature enough to complete a regeneration.
As with all filters, the DPF must be regularly emptied, if regeneration is not carried out or fails the DPF will start to fill up, eventually becoming partially blocked. A lot of DPF issues begin as passive regeneration can only occur at high speeds on a motorway, or under increased engine load, so when a vehicle is continually used for shorter local journeys, where the engine cannot get up to temperature properly this can quickly lead to the DPF blocking up.