Diesel Particulate Filters (DPF) have been around for a long time, however, after some recent research, some car manufacturers are now beginning to install petrol particulate filters, also known as gasoline particulate filters (GPF) and otto particulate filters (OPF), in some of their car models.
It was never really believed that petrol engines release harmful exhaust gases, however, during recent years, this idea has changed. The recent studies also show that large diesel vehicles emit up to 10 microns of particulate matter in diameter. To get a perspective on this, a human hair is around 70 microns. However, in 2001, the knowledge of nanoparticles came to light.
Compared to microns, nanoparticles weigh much less, however, two main concerns were raised; they exist in large quantities and are capable of covering big surface areas, and they are more likely to penetrate deeper into an individual’s lungs than larger particulate matters. Previously, the number of particulates that came from an exhaust was measured by weight but now that nanoparticles need to be considered, alternative measurement techniques can help detect nanoparticles because they do not carry much weight at all. Therefore, petrol particulate filters are designed to catch all sizes and kinds of harmful particles.
In 2009 the Euro 5 Emission Standards ensured that all diesel vehicles had a particulate filter installed to reduce CO2 emissions. Some manufacturers have equipped a Petrol Particulate Filter within some of their models, adapting and using the knowledge from Diesel Particulate Filters.
What Is A Diesel Filter?
Diesel engines burn fuel differently to petrol ones, therefore a lot of soot is created as a byproduct of the combustion process. This substance is harmful to the environment and to the health of humans, therefore, it is the filter’s job to trap and remove diesel particulate matter from exhaust gases before they can be released into the atmosphere.
The filter also has to eliminate the soot and it does this by exposing it to high temperatures, which burns the particulates leaving very fine ash residue. Unfortunately, over time, the ash will accumulate in the filter and it can eventually cause blockages, which is where the regeneration process is required. This is where the blockage is subjected to very high temperatures and then the harmless products produced can be released with the exhaust gases.
There are two types of regeneration:
- Passive regeneration: This occurs automatically when you travel on long motorway journeys, for example, and your exhaust temperatures remain at a high level for a long period of time.
- Active Regeneration: If you only make short trips in your vehicle and passive regeneration cannot occur, your engine control unit (ECU) will sense if there any blockages in your DPF and if there are, it will inject more fuel into the engine, in order to raise the temperatures in the exhaust system and allow regeneration to happen.
For more information on diesel particulate filters and why your dpf warning light may be illuminated, check out our articles – What Is A DPF (Diesel Particulate Filter) and DPF Cleaning Service – Nationwide .
What Is a Petrol Particulate Filter?
Similar to a DPF, a petrol particulate filter (PPF) prevents harmful particulate emissions. It is fitted in the exhaust system and captures soot particulates in direct-injection petrol engines. The filter is structured like a honeycomb and it is created from synthetic ceramic material. As the exhaust gas passes through the exhaust system into the filter, the soot particulates are trapped.
There is one main difference between a DPF and a PPF; a diesel filter has a larger capacity than a petrol filter, as it can hold up to 8g of soot in it and a petrol filter can only hold around 1g of soot. However, if we consider how many particulates each engine emits, a petrol engine releases 30 times fewer particulates.
Why Are Particulate Filters Important To Have?
These filters are important to have, the reason being is that the new EU regulations are aimed at reducing CO2 emissions produced by cars and other road vehicles. However, petrol engines that are for construction purposes or machinery are not included in this regulation; this is likely to change in years to come.
Particulate filters in petrol cars can help reduce the amount of pollution and harmful gasses in the air, which in turn has a positive impact on our atmosphere. With the increasing number of vehicles in use, due to the recent diesel gate scandal, more and more people are choosing to purchase petrol-fueled vehicles and other types, instead of diesel-run vehicles.
How Does The Petrol Filter Work?
Some car manufacturers such as BMW and Volkswagon have implemented Petrol Particulate Filters in a few of their new vehicles. The filter is located near the turbo and it is effective almost immediately after the engine is started.
When you are driving, the exhaust passes through the walls of a series of channels that are sealed off at different ends. The particulates that are captured are then superheated, which removes the harmful substances, leaving carbon dioxide. Concurrently, the unwanted nitrogen oxides and hydrocarbons are changed into carbon dioxide, water and nitrogen.
Once the filter has done its job, the exhaust gases pass through a three-way catalytic converter which ensures that the exhaust is meeting the latest level of the EU’s emission standards and the number of harmful pollutants leaving the exhaust is reduced.
How Does Petrol Particulate Filter Regenerate?
As we have mentioned, there are many similarities between a DPF and a PPF, one being that the filter will eventually become clogged with particulate matter (soot). Therefore, in order for a petrol filter to burn off the soot, deceleration must occur. To elaborate, deceleration can be done by pressing on the brake pedal or carrying out ‘engine braking’, which is when you release the accelerator pedal.
This then ceases the fuel injection and increases the airflow going through the engine and the exhaust system. Consequently, the temperature of the petrol filter will increase enough to ignite the trapped particulate matter.
However, in situations when deceleration is not possible, the system that controls your engine will delay the spark timing, which will create a light air-fuel ratio, or in other terms, your engine will begin to run ‘lean’. This, in turn, will allow more oxygen to be available and regeneration can be initiated.
How Can You Tell If Your Petrol Engine Has A Filter?
Not many petrol-fueled vehicles have a Petrol Particulate Filter installed. This is because currently, only a few car manufacturers such as Volkswagen and BMW have taken the initiative to install them on a few of their models. It is expected that more car companies are going to place them into their car models within the next five to seven years. As time goes on and more technology progresses, we should see a huge roll-out of filters on petrol vehicles.
It is not expensive to purchase a particulate filter, so the cost is not too high for manufacturers to install them, or consumers to buy cars that have them installed.
Petrol Particulate Filter Replacement & Cleaning
It should be noted that petrol filters are much more delicate than DPF’s, as they can’t hold as much trapped soot before regeneration is required. However, a positive is that an additive does not need to be used to assist in the cleaning or regeneration of the filter, whereas, with diesel filters, it can be needed at times.
Sinspeed is an automotive garage based in Greenwich, London. We offer a wide range of services, including petrol particulate filter servicing (cleaning) and replacement. If you find that your petrol filter is not regenerating or it has remained blocked for an extended period of time, you should consider getting it inspected. So, book in with us today, either by filling in our easy online form or giving us a call on 0203 815 9441.