What Is The Purpose Of A Diesel Particulate Filter
In order to understand exactly what causes your Diesel Particulate Filters (DPF) to fail one needs to first gain insight into the purpose of the DPF.
The primary function of the DPF in the exhaust system is to “clean” exhaust emissions before these gases enter the atmosphere. It achieves this by effectively trapping the diesel soot, harmful contaminants and particulate matter in the filter.
The Structure of the DPF
The DPF has a complex ceramic honeycomb design structure which creates a massive surface area close to the size of a rugby field when laid out. This is contained in a cylinder which is roughly 20cm x 15cm (size varies). The ceramic surface is typically enhanced by the use of precious metals such as platinum, palladium and rhodium. These help to oxidise pollutants which reduce poisonous emissions. As the exhaust gases flow across the surface area the soot and the undesirable components are trapped.
Although this honeycomb design does the job effectively it unfortunately starts getting blocked up by the soot. Ideally, when the driver follows the manufacturer guidelines, the soot is burnt off in what is called DPF Regeneration.
Herein Lies The Problem With Diesel Vehicles!
Most urban drivers travel short trips at low speeds all the time. The typical trips are to:
- drop and fetch the children from school
- go to the shops
- go to work
- visit friends and family
- travel in stop/start traffic most of the time
The other issues which make the problem so much worse are:
- not servicing the car regularly
- using the incorrect oils which contain additives which cause clogging
- using low quality diesel fuel
- regularly running the tank with low fuel
- ignoring DPF warning lights
In these cases, the DPF never gets a chance to regenerate.
This results in the DPF clogging up prematurely which can lead to catastrophic failure.
How Do You Know If The DPF is Blocked Or Not
The following warning signs indicate your DPF is getting seriously blocked:
- the engine seems low on power
- the car won’t rev up
- excessive black smoke from the exhaust
- much higher fuel consumption
- and finally, the warning light illuminates on the dash
If any of these warnings start happening – Contact GP Motor Works immediately!
How To Avoid Your DPF From Failing
So the very important question is – how do you maintain your DPF?
It is crucial to understand the DPF absolutely has to clean-out the soot which has built up in the honeycomb structure! There are two ways you can help to effectively maintain your car’s DPF and extend it’s lifespan. Both involve getting the regeneration process to work as it’s designed to do:
Passive regeneration
Frequently get out onto your nearest highway and drive consistently at the speed limit for 30-50 minutes. This means choosing a time when the highway is not busy as stop/start travelling defeats the object. This process causes the exhaust temperature to run at a higher level for an extended period. When these conditions are met – those catalyst precious metals we talked about, oxidise the soot and contaminants and the remaining CO2 leaves via the exhaust.
It is important to note this passive regen occurs naturally as long as the engine is put under consistent heavy load and higher temperatures (above 315 degrees C) for extended runs.
Active regeneration
The truth of the matter is most drivers of diesel cars simply don’t adhere to the manufacturer’s guide on how to passively regenerate the DPF.
Fortunately, active regeneration is automatically started when the soot levels reach a set limit as determined by the vehicle’s ECU. Basically, extra fuel is injected into the exhaust which raises the temperature to around 600 degrees C. This intense heat actively burns the excess soot which opens up the channels in the honeycomb structure.
The success of this process is totally dependant on ensuring the journey is long enough as well as keeping the speed above 90 km/hr.
Active regeneration is taking place when you notice the following:
- There is a change in the engine sound
- Increase in fuel usage
- Idle speed faster than usual
- Cooling fans running continuously
- Automatic stop/start is temporarily deactivated
Forced Regeneration
This is normally required when the soot levels reach around 70% and the active regeneration measures have not been fulfilled. This requires you to urgently book your car in at GP Motor Works.
We will connect a diagnostic machine and initiate the forced regeneration.
It is vital to understand that above 85% blockage the DPF system can no longer be regenerated. The unit will have to be removed and replaced. Even using a cleaning additive at this stage is unlikely to help.
Damage Caused By DPF Becoming Severely Blocked
We have written a number of real-life examples showing what happens when the DPF becomes completely blocked. This is not a trivial matter as the damage to the DPF itself as well as the connected systems can be extensive.
Basically, the exhaust gases are blocked from exiting the exhaust. This creates back pressure which damages the turbo/s chargers, cylinder head gasket and the engine. In many instances, the car may not start at all and will have to be towed in.
Our Advice To Prevent DPF Failure
There are a number of things drivers can actively do to ensure they get the best out of the DPF:
- Take frequent trips on the highway when there is little traffic (avoid stop/start)
- Use the correct oil and don’t miss the scheduled oil change intervals
- Use premium diesel fuel
- Don’t ignore the DPF warning light
If you are unsure about any of this please get in touch with us immediately.
