Volkswagen to fit filters to petrol engines as legislation looms

The ongoing scandal over diesel emissions has rocked the car world and there has been a small but noticeable shift from buying diesel to buying petrol. It’s not as dramatic as the changeover we saw in 2008 from petrol to diesel in Irish purchasing habits, but there has definitely been a turning of a corner.

Some of that is people working out that a lower-priced petrol model saves more money over the long term than a more expensive diesel, no matter the difference in fuel consumption and fuel cost, but some of it is also down to people being spooked by the sudden realisation that diesel exhaust fumes can be pretty nasty.

Particulate filters

And it’s not just the much-publicised nitrogen oxides (NOx) either - it’s also the invidious, tiny, highly carcinogenic particles of soot (commonly referred to as particulate matter). For more than a decade now, we’ve had technology to trap these particles in a filter in the exhaust (repair of which can be hugely expensive if it’s not maintained just right) but now the technology is moving to petrol engines too.

That sounds counter-intuitive. The recent rubric has been that diesel engines emit less carbon dioxide (good for the environment) but more localised toxins such as NOx and particulates (bad for us). Petrol engines were supposed to be the other way around, higher in Co2 but lower, in fact almost totally clean of, nasty carcinogenic pollutants.

Not so. Petrol engines produce much lower levels of pollutants, in general, than a diesel engine, but not none and now legislation is in place for 2017 mandating the use of particulate traps for petrol engines.

Too late

Volkswagen has this week announced that all of its TSI and TFSI turbocharged and direct injection petrol engines will be fitted with filters, starting from June next year with the 1.4 TSI VW Tiguan and the 2.0 TFSI Audi A5 being the first models to get the technology as standard.

"Particulate filters for diesel engines are already proven and established. The gasoline particulate filter will now reduce the particulate emissions of direct injection petrol engines by up to 90 per cent" said Dr Ulrich Eichhorn, head of group research and development.

However, the move to petrol engine filters, not just from Volkswagen but from all car makers and indeed legislators, comes far too late according to pressure group Transport & Environment.

James Nix, and Irish representative for T&E told The Irish Times that "the story of petrol cars with direct injection engines is another sorry one. They first came in 1997 with the Mitsubishi Charisma. It was soon realised that these engines emit more particulates. Transport & Environment pressed for particulate standards to be applied but EU law-makers first refused and then postponed the reform. All it takes is a filter costing €30 or €40. Regulation mandating this filter will only come into force in 2017; the delay of nearly 20 years is unconscionable with adverse health impacts across Europe. "

Maintenance costs

What’s not yet known is the potential maintenance cost of these new systems. When diesel particulate traps were first introduced, they were said to be maintenance-free and self-cleaning, which to an extent they are. But that depends on you driving regular long journeys, long enough for the engine and exhaust to heat up sufficiently for the cleaning to take place.

Those who bought diesel cars for low-mileage work or for mostly short urban trips soon found that their filters were clogging up, triggering massive repair and replacement bills. Some owners actually had the filters removed altogether, which will theoretically cause a failure on the National Car Test.

With petrol engines, generally, being recommended for shorter, intra-urban hops, will these new filters prove to be as fallible as their diesel antecedents?