DPF-Cleaning: Diesel Particulate Filter


1 - Why does my DPF get dirty?

The particulate filter, commonly referred to as the DPF, is mounted separately from the engine block in the same area as the catalytic converter. The DPF is responsible for removing diesel particulate matter (or soot) from the exhaust gas of a diesel engine. In order to regenerate the filter, which is continuously accumulating soot, carbon deposits must be burned off by increasing the temperature of the exhaust gas at the inlet of the filter.
During regeneration, the temperature of the exhaust gas can be regulated precisely. The transmitter informs the engine control unit (ECU) of the exhaust gas temperature. It is thus possible to calculate precisely the amount of post-injection fuel required to increase the temperature of exhaust gas during the regeneration phase.

2 - Regeneration

To prevent the DPF from becoming dirty or clogged, which consequently impairs its function, it must be regenerated regularly by a process of burning off the soot particles that have accumulated inside the filter.
The different strategies for regeneration
Passive regeneration
 Soot particles are burned off steadily without the intervention of the ECU. This is achieved at standard highway speeds (3000 r/min). The temperature of the exhaust gas will reach around 660°F - 930°F.

Active regeneration

In cases of predominantly urban use, the temperature of the exhaust gas fails to reach sufficient temperatures to achieve passive regeneration. Consequently, soot particles are not eliminated and instead accumulate inside the filter. When a clogging threshold is reached (18 grams), the engine’s computer will trigger active regeneration.

The degree of carbon accumulation inside the DPF is calculated using two models programmed within the ECU:

-    A model based on the driver profile, which calculates saturation according to a specific pattern of signals coming from the temperature transmitters of the exhaust gas as well as the oxygen sensor.
-    A model based on the flow resistance of the DPF, which calculates saturation according to signals reassembled by the differential pressure sensor, temperature transmitters, and air flow meter, which then all inform the ECU of the degree of saturation inside the DPF.

The pressure sensor measures the difference in pressure between the inlet and the
outlet of the DPF, the difference in pressure corresponding to the degree of saturation
inside the filter. The more the filter is clogged, the higher the voltage (in volts)
transmitted by the sensor to the ECU. At a specific voltage, corresponding to the
quantity of carbon particles (grams), the ECU will activate forced regeneration of the
DPF by raising the temperature of the exhaust gas to 1020°F/1200°F.

To achieve this increase in temperature, the ECU will perform several actions:

-    Regulating the flow of air through the electronic throttle control (ETC).
-    Deactivating the EGR valve from recycling exhaust gases in order to increase the combustion temperature.
-    Triggering a first post-injection following the principal injection in order to increase the combustion temperature.
-    Triggering a second post-injection, causing the unburned fuel to evaporate inside the combustion chamber. The unburned hydrocarbons are oxidized by the vapor inside the catalyst converter. The heat generated during this stage can reach temperatures of 1140°F inside the DPF.
-    The transmitter signal, located upstream of the DPF, is used by the ECU to determine the amount of fuel to be injected in the second post-injection.

Forced regeneration 
On very short drives, it is impossible to reach the temperature needed to regenerate the DPF. If the saturation level reaches a threshold of 24 grams, the indicator lights on the DPF will cluster.

This signal prompts the driver to perform a regeneration route; that is, to run the vehicle at high speeds over a certain distance in order to reach temperatures sufficient for the regeneration of the DPF.

 Manual regeneration
If the forced regeneration is not successful and saturation has exceeded the threshold to a level of 40 grams, in addition to the appearance of the glow plug and engine light warning indicators (see below), it is necessary for the driver to take the vehicle to the dealership or a garage.
In this case, active regeneration is blocked by the ECU in order to prevent degradation of the filter. At this point, the DPF must be regenerated in a garage by experienced technicians.

In this case, active regeneration is blocked by the ECU in order to prevent degradation of the filter. At this point, the DPF must be regenerated in a garage by experienced technicians.
If saturation has exceeded a threshold of 45 grams, regeneration is no longer possible. At this point, there is too much risk that the DPF will be faulty and must therefore be replaced.
Kilometer regeneration

This method of regeneration depends on the distance traveled. It safeguards the DPF from exceeding unhealthy levels of saturation. The ECU automatically triggers active regeneration when no regeneration has been activated in the last 750-1000 kilometers, regardless of the saturation level.

3 - Carbon Cleaning regeneration

Carbon Cleaning is the least expensive method. Performed without disassembly and requiring very little intervention time. It is a breakthrough alternative eliminating the need to replace expensive parts, possible thanks to the specially designed hydrogen treatment. This treatment can be done every 10,000 miles, in order to prevent any risk of excess saturation. In addition to acting as a preventative measure, the treatment can also resolve existing problems with the DPF. In effect, the Carbon Cleaning solution is your alternative solution prior to having to resort to replacing your expensive engine parts. The cost of the service is $95