OPF (Otto Particulate Filter) & Particulate Matter.

01.Different fuel, new filters - old problems?

The idea is the same, but the implementation is different. With the introduction of the Euro 6d TEMP emissions standard, gasoline engines are now also required to emit only around ten percent of the usual amount of soot.

Vehicles powered by gasoline are therefore now subject to identical requirements as diesel vehicles.

This means that in the future it will also be necessary to install a particulate filter in gasoline vehicles – as an additional component to the catalytic converter. A complete solution is offered by the 4-way catalytic converter, which contains a particulate filter and catalytic converter in a single component.

This is because a gasoline particulate filter reduces and traps the soot particles (ultra-fine particles) that are harmful to health and the environment from the exhaust gases and lowers the emission values in combination with a catalytic converter.

And of course, gasoline particulate filters will also clog after a while.

02.OPF - design and differences to diesel particulate filters.

In terms of design, an OPF differs only slightly from a diesel particulate filter. The ceramic body is provided with alternately sealed honeycombs. The ceramic surface is coated with a highly heat-resistant coating. In addition, a so-called washcoat with a precious metal coating has been applied. The exhaust gases coming into contact with the surface are chemically broken down in this and eventually oxidize. The solid particles are deposited and burned off by the exhaust gas temperature. Due to the porous ceramic, only cleaned and filtered exhaust gases can leave the gasoline particulate filter.

03.Why is a particulate filter now also important in gasoline engines?

Why do Otto particulate filters suddenly have to be equipped with a filter at all? Why are there suddenly residues that have to be reduced?

Sooty, high-emission diesel cars have long been a thing of the past thanks to the use of modern combustion processes and particulate filters. We were able to make an important contribution to this with our innovative process for DPF cleaning.

However, it is becoming increasingly apparent that gasoline vehicles with their modern, highly supercharged gasoline engines with direct injection – or especially because of them – also release fine particles during combustion. Here, a large proportion of the soot is produced by the combustion of engine oil in the cold-start phase. With the introduction of direct injection, the fuel injected into the combustion chamber now also does not burn completely, and soot is produced. However, the particles emitted by a gasoline engine are much smaller than those emitted by a diesel engine. Due to their respirable nature, these ultra-fine particles are a great danger to our health. As a result, the automotive industry is generally striving to produce gasoline engines that are as fuel-efficient as possible, with high injection nozzles and high turbocharging pressure. It is only with such passenger cars that the phenomenon of ultra-fine particles increasingly comes to the fore.

In fact, the problem has only become increasingly apparent in recent years due to the spread of turbocharged direct-injection engines. The problem here is that these have difficulty converting the fuel into a gaseous aggregate state during the cold-start phase.

This, in turn, results in comparatively unclean combustion, which in turn leads to greater soot formation.

The legislator’s response to this was to introduce limits for particulate emissions from gasoline engines as part of the Euro 6 emissions standard – this has applied to all newly registered cars since September 2018.

This means that gasoline engines now have to comply with the same particulate limits as diesel engines.

With the introduction of the OPF/ BPF, fine particles produced during combustion in gasoline engines can now also be effectively captured and the high emissions reduced.

04.Since when have gasoline engines been equipped with particulate filters (OPF)?

With the introduction of the Euro 6 emissions standard, gasoline vehicles must now also comply with stricter limits. The Euro 6 emissions standard includes limits for hydrocarbons (HC), nitrogen oxides (NOx), carbon monoxide (CO), non-methane hydrocarbons (NMHC), particulate matter and particulates. The Euro 6 emission class is divided into Euro 6b, Euro 6c, Euro 6d-Temp and Euro 6d:

Newly designed gasoline vehicles and vehicles with new type approval have had to comply with the Euro 6c standard since 2017, Euro 6d-TEMP from 9/2019 and Euro 6d from 01/2021. The limits of the Euro 6 standard remain the same. In the WLTP measurement procedure, diesel cars must not exceed the NOx limit of 80 mg per kilometer and gasoline cars 60 mg per km. To comply with the standards, OPFs are used for gasoline vehicles and DPFs for diesel vehicles. In addition, catalytic converters or catalytic coatings are required, which break down and clean the harmful exhaust gases through a process known as catalysis.

There are also corresponding deadlines for vehicles that have already been built and are in production. Older, already registered vehicles are not affected. Here, there is still no concept / legal basis for a possible retrofit.

05.Do I now have to retrofit my gasoline engine with an OPF as well?

What does this mean for drivers who already drive a gasoline engine but do not have a particulate filter? Can they expect to have to retrofit the filter – and thus have to pay a lot of money?

No! Existing vehicles are not to be affected by the new regulations. Retrofitting the OPF is currently neither planned nor possible.

This is because a filter – as a fine-pored ceramic body – inevitably increases backpressure. It would therefore be necessary to adapt all processes from injection to the dimensioning of the catalytic converter to this, which is not readily possible in the context of a retrofit.

Instead, the technical solution of the future is to increasingly install so-called four-way catalytic converters, in which the particulate filter is already integrated into the usual three-way catalytic converter.

06.Do gasoline particulate filters (OPFs) also clog?

Regeneration options:

With the introduction of this technology, gasoline vehicles now also have the vehicle’s own regeneration mode for the particulate filter, as is the case with diesel vehicles.

On the one hand, there is continuous regeneration
An initiated regeneration (e.g. in case of increased differential pressure, cyclic)
And the workshop regeneration / forced regeneration

It remains to be seen which exhaust gas cleaning solution/regeneration option the individual manufacturers will use.

OPF – Cleaning

Like the DPFs, which were originally believed to be maintenance-free, the OPFs will also reach their collection capacity after a certain mileage. Presumptions are that they will last around 160,000 tkm /10 years. During combustion, however, the ultra-fine particles of minimalist size produced by the hot gasoline exhaust gas are supposed to burn so optimally that only a minimal amount of solids needs to be collected in the filter. As a result, it should take much longer for them to clog the OPF or for the filter to reach its maximum saturation level.

Whether DPF or OPF: the filters are catchment vessels for the soot and ash particles resulting from combustion.

Vehicles that only travel very short distances and go through frequent cold-start phases are more likely to reach their maximum capacity here, but probably also vehicles with direct injection.

How defects in sensor technology and add-on parts, as well as the quality of fuel and oil, will affect the longevity of gasoline particulate filters will become clear in the coming years.

In this area, there is still a lot of educational work to be done due to information gaps and lack of experience7.

Barten GmbH, as a specialist cleaning company for particulate filters, is already working on an adapted, resource-saving, quality-assured and low-cost cleaning alternative for gasoline particulate filters.

07.Otto particulate filter: technical solution with a future.

Many of the vehicle manufacturers have already started to equip the current gasoline engines with particulate filters. It is a fact that at the same time as the filter is fitted, fuel consumption increases, but CO2 emissions are reduced.

So do millions of gasoline car owners have to expect similar challenges with regard to DPF cleaning as diesel drivers?

In order to be able to give clear answers to this question, more research is certainly needed.

If experts are to be believed, however, the service life of gasoline particulate filters corresponds to the service life of the vehicle in question. Some manufacturers give more specific information on this – and state a period of 15 years before the purchase of a new OPF becomes necessary.

From a technical point of view, the gasoline engine has an advantage over the diesel engine in that it reaches a high exhaust gas temperature in a shorter time, which means that the automatic regeneration of the particulate filter can be initiated sooner – i.e. more frequently.

During regeneration – as with the DPF – soot particles deposited in the filter are burned to small ash residues by passing hot exhaust gas.

This more frequent regeneration means that active regeneration of the particulate filter is needed much less frequently compared to an engine with a compression ignition system.

However, even if it seems that the amount of ash in the OPF increases more slowly, sooner or later the time will come when professional cleaning or filter replacement is necessary.

This is exactly what we at Barten GmbH are already well prepared for. We are continuously developing new and innovative solutions for cleaning gasoline particulate filters.

08.Ultra-fine particles: a novel load.

We are talking here about ultra-fine particles, which at the same time represent a new kind of burden for humans and the environment. These are so small that their mass (and therefore also their weight) is almost immeasurable. This is also the reason why these new dangers have received so little attention so far – they have simply not been perceived properly!

However, the number of these ultra-fine particles in exhaust emissions is so high that they pose a threat to our health and the environment if no adequate countermeasures are taken. The tricky thing is that the ultra-fine particles are particularly respirable due to their minimal size: they are not filtered by the nose, can quickly and easily penetrate the human body, finally pass through the alveoli in the lungs and are therefore particularly dangerous – favoring the development of cardiovascular diseases in the long term. What is required is fast action!

09.What are the designations for gasoline particulate filters?

• GPF is the abbreviation for “gasoline particulate filter”.
• OPF (gasoline particulate filter)
• BPF (gasoline particulate filter)
• Other names for gasoline particulate filters are:
• ORPF (gasoline particulate filter)
• BRPF (gasoline particulate filter)
• RF (soot filter)
• RPF (Soot Particulate Filter)