Made indispensable by direct injection, the GPF is similar to its diesel counterpart, but is more easily self-cleaning.
Until a few years ago, the term 'particle filter' was unequivocally associated with diesel engines.
First introduced on the threshold of the new millennium, when the common rail gave birth to generations of higher-performance diesels thanks to a finer combustion process, it was used to combat the so-called fine particulate matter or PM10, 'captured' by a special filter that on the most advanced systems is capable of self-cleaning.

The formation of particulate matter, however, does not depend on the type of fuel but on the type of combustion, specifically that of direct injection engines, which allow for better vaporisation of the fuel resulting in lower fuel consumption but have among their side effects a higher amount of fine dust in the exhaust.
Particulates that are reportedly hundreds of times higher than indirect injection systems, and 10 times higher than diesel.
With the technological revolution that has brought this device to spread rapidly even on petrols, the problem of particulate matter has therefore become commonplace.
So much so that, starting with Euro 5, anti-pollution regulations have set specific limits for these engines too, making it necessary to equip them with specific filters (some manufacturers, however, such as Volkswagen and PSA, were already working on this).

Particulate filters for petrols, also called 'GPF' (Gasoline Particulate Filter) have the same function: they consist of a duct with very thin channels lined with materials that attract and retain fine particles, and as on diesels they are equipped with regeneration systems that clean them by burning off accumulated dust to prevent them from clogging.
On diesels, this cleaning takes place by means of a specific procedure that temporarily raises the temperature of the exhaust gas by a few hundred degrees through afterburning.
This is achieved by injecting fuel when the gases are close to leaving the cylinders or through an additional injector positioned in the exhaust, which activates post-combustion directly at the filter inlet.

Particularly in the former case, however, the engine must be running at constant speed and not idling for a few minutes at the time of regeneration.
Hence, the need for a warning light that informs the driver of the need to facilitate the procedure by driving a few kilometres on the ring road, for example, to put the engine in ideal conditions.

For petrol engines, on the other hand, the process is much simpler because combustion generates higher temperatures and thus hotter gases.
Thanks to this - and the use of specific filter materials such as Cordierite and injection optimisation - cleaning does not have to be commanded at a specific time but takes place practically continuously and without the driver having to do anything special.

The sensor technology of this type of system remains unchanged compared to that fitted to diesel engines.
The sensor technology of this particulate filter remains unchanged compared to diesel engines. The two exhaust gas temperature sensors (upstream and downstream filter), differential pressure sensor and the two upper and lower lambda sensors remain.

On behalf of the Technical Help Desk team, I thank you and wish you good work.

• GPF