How do they filter?
The have a ceramic core full of small but deep cells.
Alternate cells are blanked off at either the front or the back, meaning that any gas is forced through the wall into an adjacent cell.
This leaves the soot embedded on the surface of the wall.
How do they clean themselves?
As the cells progressively fill with soot , more and more of the cell’s wall is blanked off which gradually increases the exhaust back pressure.
This back pressure is measured as “pressure differential” between the front of the DPF and behind the DPF by usually two small rubber hoses that lead to a variable switch, called a “Pressure Differential Switch” or “Pressure Differential Sensor”
The time this filling process takes varies with the management strategy devised by the manufacturer but typically is around 800 to 100 kilometres.
Subaru and some others use a shorter cycle of around 150 kilometres. So they have more frequent, but shorter regeneration.
Types of sensors present (temperature, O2 and Pressure) and their role
Pressure Differential Sensors or switches measure the exhaust back pressure and signal the cars ECU about the DPFs soot loading. The ECU thus knows when to regenerate the DPF.
They are usually mounted on the transmission tunnel or engine firewall and are connected to the DPF by two rubber hoses, to the front and rear of the DPF s internal ceramic core
Temperature Sensors measure the exhaust gas temperature (EGT) and so allow the computer the ability to thermostatically control the regeneration temperature.
How long do DPFs last?
Variable, but if all goes well a minimum of 200,000 km’s can be expected. With perfect service and driving conditions up to double this is possible.
Often a fault can develop with the vehicle, such as leaking fuel injectors faulty sensors, induction leaks etc that can shorten the life of the DPF.
I do know a customer who managed 500,000 Kms out of his original Mercedes Sprinter DPF without cleans or replacements!
Two ways they can fail, eg Blocking or melting
1-Usually DPF failures are a blockage caused by soot. This is because the DPF is not able to burn it off.
Either the car’s ECU is not aware of the pending blockage (sensor failure) or it’s inability to cope with the huge amount of soot being produced due to a mechanical fault with the vehicles systems.
2-A DPF’s core can be cracked or melted due to overheating. Overheating can be caused by the temperature signal not being accurately transmitted to the ECU or by a mechanical failure in the vehicle’s which allow an uncontrolled flow of either engine oil or diesel fuel into the DPF.
Service the vehicle meticulously.
Use the best oil.
Buy fuel from a high volume, reputable brand service station, probably also on a main road.
If the vehicle is used in a metro environment try to take a 1/2 hour to 1 hour trip on an expressway or country road at least once each fortnight.
Consider the following ;
Don’t use additives either fuel or oil. They may be compatible but they may not. Don’t gamble.
So your DPF dash light has come on!
If the car is still running well, try a 1/2 hour drive on a highway or freeway, dropping down a gear or two so as to bring the engine rev’s up to 2500 approx so as to help geerate more exhaust heat and allow the vehicle to perform a “passive regeneration” by itself.
If that fails taker it to your repairer and ask him to check the car with his Scan Tool.
At this stage a “forced regeneration” performed by the Scan tool would be the next option.
Subject to the cars mileage it may become necessary to further investigate possible mechanical failures in the vehicle.
DPF replacement is the last option and only when the cause of the existing failure has with reasonable certainty been identified and corrected.
Repair Options ?? CALL US !
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