Trust us on emissions, says Benz

Mercedes-Benz’s industry-leading decision to install particulate filters across its entire petrol engine fleet is designed to avoid any debate about their cleanliness in an era where car manufacturers are under fire for emissions cheating.

While Volkswagen has copped the brunt of the opprobrium so far, Benz has also been in the firing line, as we reported earlier this week, for switching off the emissions cleansing systems in some Bluetec diesel-engined models at temperatures below 10 degrees Celsius.

While much of the focus has been on diesels and NOx emissions, the issues of effectively screening health-damaging particulates in the latest generation high-tech direct-injection petrol engines has been a quietly developing issue.

And as emissions regulations get tougher it’s only going to be amplified more. For instance, the Euro emissions standards which Australia is aligning itself with specify a particle matter limit for direct-injection petrol engines.

“We don’t want to end up in a discussion whether gasoline engines do have a particulate problem,” Mercedes-Benz powertrain vice-president Bernhard Heil told motoring.com.au at a future drivetrains media briefing in Stuttgart last week.

“That’s why we proactively said ‘OK we would like to do the step to provide the cleanest situation that is feasible and that is the particulate filter for the gasoline engine.”

Heil talked up the quality of Benz’s Piezo injector system co-developed with Bosch, but would not bite when asked where other manufacturers stood in comparison and if they should have already moved to a particulate filter.

“I am not commenting on that,” he said. “This injection system from Bosch is a complex system and it’s also not a cheap system, which is maybe why it was easier for us to afford that (particulate filters) compared to one or the other of the competitors.

“We anticipated that at some point emissions is always a challenge and how to do that next steps and that was the reason why we introduced those particulate filters on the S 500; let’s get prepared for introducing those particulate filters and now we have had those positive experiences what could be the next step for us?

“We are not looking to the others for what they are doing. We want to be a company that is trustful and well prepared and we want to do a little bit more for the environment than the others.”

Particulate filters are nowadays universal fitment in turbo-diesel engines. Particulate matter is a known cause of cancer, asthma and cardiovascular diseases.

While direct injection turbo-petrol engines still produce less particulate matter than diesels, it is of an ultra-fine nature.

Naturally-aspirated and port-injected petrol engines have less of an issue but Heil called for all manufacturers to follow Benz’s lead and install particulate filters across all petrol engines.

“I personally think so,” Heil said. “We at Mercedes-Benz do think that the particulate filter should be a general technology in all gasoline engines. We are not questioning whether it is a direct-injection engine or a port-injection engine.

“There are some examples of port-injection systems being easier to comply with particulate numbers, but they are mainly naturally-aspirated engines. They have more chances.

“Turbocharged port-injection engines are not that much different compared to direct-injection engines.”

Benz has been testing particulate filters in the 4.7-litre biturbo petrol V8 engine of the S 500 saloon for more than two years. It will start the widespread introduction of particulate filters across its petrol engine range when the new inline six-cylinder family debuts in the updated S-Class late in 2017. It will gradually replace the current V6 engine family.

“We have them (particulate filters) in the V8,” said Heil. “We will introduce them in the inline six. We will introduce them in the four-cylinders. We are starting with the S-Class facelift, but then it goes immediately in all the other vehicles.

“From the facelift S-Class we will also have the V6 with particulate filters.

“We will not retro-fit vehicles in the field because that would be too much of an effort since you would have to replace the entire after treatment system, which is prohibitive from a cost perspective.”