How VW cheated

What’s at the root of the Volkswagen emissions scandal? Essentially, VW engineers installed software into four-cylinder diesel engines fitted to Audi, Skoda, and Volkswagen cars designed specifically to fool the system.

So let’s start with the emissions test. The New European Driving Cycle, which dates back to 1997, is supposed to represent the typical usage of a car in European conditions. It was originally designed for petrol vehicles, but is now used to measure emissions on diesel engines as well as estimation of electric power consumption in electric and hybrid electric vehicles.

Essentially, it’s a cycle of tests which consists of four repeated urban driving cycles and one extra-urban cycle.

However, for years it has been obvious that the cycle is NOT representative of normal driving in 2015, although it was probably fine for conditions in 1997. Times have changed; cars are more powerful, so they are driven harder, brakes applied more often, and idle longer in traffic.

That said, the latest Euro6 emissions standards are hard to meet, especially for diesels, with the big factor being the removal of harmful NOx – nitrogen oxide – which has been attributed to thousands of deaths through respiratory failure across Europe. To meet the emissions standards, a number of devices are fitted to the diesel engine’s exhaust. These are: 1. Oxidation catalytic converter. This converts hydrocarbons and carbon monoxide into water vapour and carbon dioxide. Particulate filter. This reduces the sooty particles emitted from a diesel’s exhaust. Exhaust gas recirculation. This is the vital one, since it lowers temperatures to prevent the formation of NOx. But the problem is, the more it is used, the more performance is affected. NOx storage catalytic converter. This reduces NOx to nitrogen and water vapour. The VW engineers realised that they couldn’t get the sort of performance they had been boasting about while the NOx controls – specifically exhaust gas recirculation – were operating fully.

So what they did was to embed software into the vehicle’s electronic control unit (ECU) which would use the car’s various sensors to detect when the car was on a rolling road testbed rather than on the open road. It would detect the test cycle, and it would also detect that the steering wasn’t being turned or the brakes being used.

It would then turn on the full emissions controls, notably the gas recirculation system, and would provide the testers with results that would indicate the car was meeting the emissions standards.

However, once the car was driven off, the software would alter the gas recirculation, thus increasing power – and NOx emissions would zoom up by as much as 40 times the allowed limit.

So who is to blame? Well it’s not just the VW engineers, although they acted dishonestly. The fact is, the test cycle is totally ineffective in giving real life figures, and must be changed.

The good news: a new test has been devised which takes into account today’s conditions, and it is this test, the World Harmonised Light Vehicles Test (WLTC), due to start in 2017, that has been used by Adac, Europe’s largest motoring organisation, to try to discredit manufacturers.

Adac says several manufacturers other than Volkswagen did not meet the Euro6 emissions standards when it recently compared vehicles using the WLTC test – but it must be stressed that they don’t have to at this stage!

What’s going to come out of this? Hard to say, but certainly diesel engine manufacturers will be working full tilt to make sure they honestly meet the required standards by the time the WLTC test comes into play in 2017. Which means we’re going to get less NOx pollution, and more-honest test figures. And that can’t be bad.

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