Exhaust Talk: Episode 03 | GPF Exhaust Filters Explained

Posted by Jake Wilmott

Returning for more answers to your questions with Exhaust Talk.

Episode 03 looks in more detail at the GPF filter also referred to as the OPF or PPF.


What is a Gasoline Particulate Filter (GPF)?

Referred to as a GPF, OPF or PPF this filter is installed into your exhaust system from factory to reduce the level of pollutants emitted from our vehicles, similar to a catalytic converter (if you missed The Cat Debate catch up here >)

Often likened to a brick sponge, the GPF filter looks similar to a catalytic converter in regard to its honeycomb structure of chambered channels, these chambers trap soot particles from the exhaust gasses and burns them off by performing a regeneration when the exhaust is at a high enough temperature. 

GPFs are incredibly efficient at their job and capture more than 90% of the airborne soot particles that will be present in your exhaust system and would otherwise be released into the atmosphere.

What issues does the GPF cause?

The main restrictions caused by the GPF are sound and performance. Comparable to having a conversation and then inserting a sponge into your mouth, the sound and flow of your voice is disrupted and creates a muffled sound, this is similar to how the GPF works on your exhaust system and explains why performance cars are now leaving the factory sounding more tame than their predecessors.

This has a similar effect on performance in terms of restrictions, whereas previously to achieve more power we can install a more free flowing downpipe to allow the exhaust gasses to be pushed through the system more efficiently, to do this and leave the GPF in place would be very counter intuitive and would free up space and flow through the downpipe sending them straight into the bigger restriction that is the GPF ultimately creating more back pressure.

Can we just remove the GPF filter?

Technically yes, however this will deem your vehicle unfit for road use and will not allow your car to pass an MOT. GPF delete pipes are produced entirely for motorsport and off-road use and should not be installed to any road going vehicle.

How do I know if I have a GPF on my vehicle?

As a general guide if your car was produced after September of 2018 and has a GDI petrol engine (Gasoline Direct Injection) the chances are it will also have a GPF equipped to its exhaust system.

The Cobra Sport Solution

Extensive testing has enabled the Cobra Sport Development team to grasp the characteristics of the GPF filter and how it effects engine tone. The development process played a huge role in recognising exactly how the GPF filter soaks up the sound when exhaust gasses pass through.

Understanding the GPF allowed the Cobra Sport team to produce a range of GPF-back systems that produce a comparable tone and performance output to their previous cat-back exhausts giving you the audible emotion you want to experience from your car without the concern of its legality.

 All Cobra Sport exhausts utilise precision TIG-welding techniques for exemplary fit and finish - a feature that gives Cobra Sport an advantage over other manufacturers. With over 25 years in the performance exhaust industry, each Cobra Sport exhaust system is designed, manufactured and tested in Sheffield, the heart of the UK steel industry.