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When Volkswagen Tried To Cheat Fuel Emissions Systems

Modern fuel tanks are fitted not only with a pressure relief valve but a range of different sensors, systems and fail-safes designed to keep people safe but also ensure that its operator meets appropriate emissions standards.

This is not only true for static fuel storage but also in the automotive world, to ensure that passenger vehicles are not emitting potentially harmful gasses at pedestrians.

One of the biggest examples of why this was needed was when one of the biggest and most trusted car manufacturers in the world tried to cheat that system.

Dieselgate, or Emissionsgate, centres around a test undertaken in 2014 by the International Council on Clean Transportation that aimed to test cars made for the American market against European tests, as the former was more stringent than the latter at the time.

The ICCT test found a rather shocking and alarming result; whilst a BMW X5 that was also tested had largely similar and expected results to their initial hypothesis, two Volkswagen cars had significantly higher levels of nitrous oxides, a pollutant that was strictly controlled in cars due to its potential risk as a carcinogen.

This was significantly different to its results in laboratory conditions, leading to two possible conclusions; either the ICCT had managed to get their tests wrong repeatedly, or Volkswagen was cheating the emissions tests.

It turned out that the latter was the case using a system known later as the “defeat device”.

 The system’s inner workings are exceptionally complex, but the basic way the system worked was that an aspect of the engine control management system could detect when it was on a rolling road, a treadmill for cars that were used to perform a range of tests.

It did this by checking the speed, the position of the steering wheel and how long the engine was in operation and measuring them against the procedure used for American clean air tests.


It would ensure that the emissions were low enough to pass those tests and then switch to a more polluting engine map during regular vehicle operation.