As the owner of a 1.6 TDI, your vehicle is equipped with a particulate filter (DPF) as standard. This anti-pollution provision is, however, responsible for a good number of problems. We will detail them for you in this article to help you better understand what is hidden behind this part, and especially behind its malfunctions on this engine.
Operation of the DPF
A particle filter is an “anti-pollution” device, which captures fine soot particles (black smoke and other poor combustion products), stores them, then burns them during a cycle called regeneration. Thus, these micro particles become nanoparticles, undetectable (or almost) by particle measuring machines.
The effectiveness of this “anti-pollution” system is therefore highly questionable, given that it only transforms particles into even smaller and less detectable elements. But its operating principle is as described above.
Regeneration of the DPF
Principle
The particle filter becomes loaded with soot during engine operation. This load is measured using pressure sensors, which measure the extent to which the passage of exhaust gases is “obstructed” by stored particles. This charge corresponds to a total weight of stored particles. Once the limit (“storage”) value is reached, a regeneration, i.e. a process of “emptying” the DPF, begins. During this process, fuel is injected at the end of combustion into the cylinder (post-injection), just before the exhaust valves open. This allows the fuel molecules to pass through the exhaust pipes and the turbo, to arrive in the particle filter, where it will be burned thanks to a process which alternates enrichment phases (to therefore provide a surplus of fuel) and depletion (to provide a surplus of air necessary to burn the residues in the DPF mixed with the fuel).
On 1.6 TDI engines, the moment of regeneration is the only moment when the lambda probe, present at the inlet of the DPF, starts to regulate combustion in the DPF, i.e. to measure the stoichiometric ratio (air/fuel ratio) to best adjust the injection for rapid and efficient regeneration.
Enrichment is done through post-injection, i.e. injection at the end of the combustion cycle. The depletion is done by reducing the quantity injected to preserve part of the clean air which enters the cylinder, to make it come to fuel the combustion in the DPF. Regeneration lasts on average 2-3 minutes for a charged particle filter in perfect condition, and between 20-30 minutes for a particle filter at the end of its life.
DPF regeneration status
The particle filter is either in regeneration mode (1) or inactive mode (0).
The transition from one to the other is done via the differential pressure parameters, the only way to measure the "filling" rate of the DPF. This setting can be checked in the “Advanced value measurements” with the VCDS or any other OBD diagnostic tool. The computer can remain stuck in the regeneration state: when the latter fails (contact switching off before the function is completed), it will restart automatically during the next restart if the ash threshold is not reached.
DPF thresholds
By particle filter thresholds, we must understand limits:
- differential pressure (pressure difference between the inlet and outlet of the DPF) maximum and minimum
- minimum temperature (to start a regeneration) and maximum temperature (to avoid causing a fire) in the particle filter
- soot rate measured and calculated (using a conversion factor of the differential pressure into soot rate) maximum (launch of a regeneration) and minimum (from when the regeneration is considered sufficient, i.e. not need to restart it on the next reboot)
Forced regeneration
Terms
The forced regeneration of a particle filter on these engines can occur in several ways:
- indicator light on the dashboard
- strong burning smell from the exhaust and in the passenger compartment
- idle speed which rises to 1000 rpm instead of the usual 780 rpm when the vehicle is stationary (red light, stop)
- engine which exhibits “shaking” and operation is noisier and “stronger” than usual (injectors clicking, engine shaking shortly after starting when the vehicle is stationary, etc.)
- a slight loss of power during the regeneration phase described above, due to reducing the injection to start the process downstream of the engine
- motor fan running at full speed despite the fact that the outside temperature is not necessarily high
- more or less thick white smoke (this often depends on the time of year and especially the outside temperature)
Solve the problem
The problem of the DPF which smokes white or regenerates on each restart can be solved in 3 ways:
End the current forced regeneration
Drive for at least 30min once the engine is up to temperature (so around 40-45min in total), preferably on the cruise control on a highway/motorway, without pushing the vehicle into revs, this slows down the process, you are on a vehicle recent, not an ancestor of the 90s, regenerations are managed by the computer autonomously, hence the preference for driving through the regulator, this allows the computer to best manage the parameters to regenerate as quickly as possible
Replace the particle filter
If the latter regenerates too often, its efficiency is almost non-existent, it leads to overconsumption and causes high temperatures during each operation, in fact it is easier to replace it. This operation requires recoding to let the computer know that the particle filter is starting new, so that it resets all the aging coefficients to zero.
Remove the particle filter
A much less expensive, faster and very effective operation, removing the DPF allows for numerous savings (fuel consumption -20% on average, much less expensive part), however it is not accepted by technical inspection and prohibited on the road.
We offer you all the parts necessary to carry out this removal as well as mechanical intervention services (contact us):