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What is a DPF or OPF exhaust?

A guide from bravoauto to DPF and OPF systems.

What is a DPF or OPF?

DPFs are found in diesel engine cars and stands for Diesel Particulate Filter. OPFs are found in petrol engine cars built since September 2018 and stand for Otto Particulate Filter. These systems work in very similar ways and are part of the exhaust. They force the exhaust emissions through the filter which then captures many of the harmful emissions produced by the engine. In this guide we’ll discuss both systems in more detail. 


How do they work?


DPFs and OPFs are part of the exhaust system of diesel and petrol cars. From the outside they appear as metal cylinders attached to the exhaust. However, on the inside of these filters there is a fine mesh which collects particulate emissions produced by the engine before they are released into the environment. The filter burns these particulates into arguably less harmful gases which are then passed through the exhaust and into the atmosphere. 
DPF filter on used bravoauto car


bravoauto technician completing 150 point safety check on used car

Why are they needed?


The filters are needed to help reduce the harmful particulates and emissions that are created from burning fuel. The emissions produced such as carbon dioxide contribute to global warming and the particulates such as soot contribute to poor air quality and have been linked to health issues such as asthma. 

Exhaust filters such as DPFs and OPFs greatly reduce the particulates emitted into the environment which helps keep the air cleaner and reduce the negative impact of burning fossil fuels.
 


Is DPF failure common?

Many people think that DPFs can reduce reliability of diesel cars and are prone to failure. However, these components are engineered to last with the correct use.

DPFs need to hot to allow for the particulates to burn off and keep the DPF clear. If you have a diesel car and only do short trips this prevents the engine reaching its ideal operating temperature. As a result, the engine produces more soot and the DPF does not warm up enough to burn off soot captured. If you regularly do short journeys this can then cause the DPF to clog.

To look after the DPF go for a long drive every 1,000 miles which will allow everything to heat up enough to clear the filters. Many cars can also run a regeneration cycle which manually burns off the DPF to clear it.

If you frequently do long journeys, you are unlikely to have a problem with the DPF. OPFs are not as prone to clogging up because petrol engines warm up quicker and run at higher temperatures which allows the OPF to clear.

DPF exhaust on car


bravoauto car driving along the road

The benefits and compromises of DPFs and OPFs


DPFs and OPFs do not reduce performance or increase fuel consumption. Instead, the computer controlling the car’s functions may reduce the amount of power produced to compensate for the filter. This is to ensure that fuel economy is not reduced. 

DPFs and OPFs can reduce the noise emitted by the exhaust which for most cars is another positive of these systems. However, for a few cars such as high-performance models, enthusiasts may miss the added noise of exhausts without OPFs fitted. 

The benefits of DPFs and OPFs to the environment far outweigh any possible drawbacks.