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Volkswagen emissions scandal: No smoke without fire

Published 25 September 2015

This isn’t about CO2 emissions. Though if it wasn’t for EC legislation seeking ever-lower CO2 emissions from vehicles, we wouldn’t have so many diesels.

On average, diesel engines are more fuel-efficient and emit lower CO2 than petrol engines and, since the EC will fine manufacturers for making cars emitting a corporate average of more than 130g/km CO2 over 2015, they have to make a lot of diesels to bring their corporate average CO2 down.

CO2 is measured in a prescribed series of lab tests carried out by manufacturers in the presence of officials to measure a car engine’s fuel economy and CO2, which are inextricably linked.

Naturally, manufacturers optimise their engines to get the best possible results in these tests, including using only the very best fuels and calibrating the engines accordingly.

However, out there in the real world when cars are not being put through the strict test cycle, they behave differently. They aren’t as fuel-efficient and correspondingly they emit more CO2. About 20 per cent more on average in the 68,134 real-life fuel economy results submitted in Real MPG.

Much the same applies to lab testing for NOx emissions. These are emissions of Nitrogen Oxide from the combustion process which, when combined with Oxygen in the atmosphere, form Nitrogen Dioxide and tiny particles of soot, that cause respiratory diseases and create ground level ozone

What the Volkswagen scandal is about is not that its engines are optimised for low NOx emissions, it’s that the engine’s computer recognises it is being tested for NOx emissions and minimises NOx emissions only for the tests.

And that’s why Volkswagen is being accused of cheating.

However, the biggest problem with NOx is the concentration of it in cities, with big numbers of vehicle movements and lots of people. It’s not so much of a problem out in the countryside.

So if the test regime recognised by the car’s computer is roughly equivalent to the car being driven in an urban environment, then it will be reducing NOx where NOx can do the most harm.

Nevertheless, heads have rolled. At least three of VAG’s top people have fallen on their swords. There will be more.

Should Volkswagen diesel owners (including owners of Audi, SEAT and Skoda diesels) be worried? Can the engines easily be fixed? We’ll get a lot more news on Friday 25th September.

It is thought that the only engines affected are EA189 common rail 1.6 TDI and 2.0 TDI fitted with diesel particulate filters.

There may or may not be a problem with the latest EA288 manifold-in-head 1.6 TDI and 2.0 TDI, many of which use SCR AdBlue systems to clean up their exhaust emissions.

Obviously Volkswagen’s reputation has taken a knock. And this will affect values in the short term. Whether values will bounce back in the long term is another matter. I think they will.

Read all the latest news on the emissions scandal

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