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# 5.4 Cheating on emission standards

So far, all of the emissions performance data given has been under ‘standard driving cycle’ conditions. This raises the interesting possibility that a car’s computerised engine management system might be able to recognise when the car was being ‘tested’. It could then comply with the NOx emission regulations by limiting the peak power but ignore them otherwise.

In late 2015 the head of Volkswagen’s US business admitted to a US court that some of their cars had such a system. In 2017 the company agreed to pay US$4.3 billion in civil and criminal damages in the US. The company admitted that its specialists were not able to reconcile the conflicting goals of fuel economy and emissions, given the competition from hybrid petrol-electric cars (described later). Worldwide Volkswagen were forced to buy back hundreds of thousands of vehicles. By the end of 2018, the cost to the company was US$21 billion.

In 2016 the humorous scientific magazine Annals of Improbable Research awarded the ‘Ig Nobel Prize’ in chemistry to Volkswagen for this elegant method of ‘solving the problem of excessive automobile pollution emissions’.

The effect on the ‘green credentials’ of diesel cars has been considerable with calls for them to be banned from many European cities. The scandal has seriously assisted the move from fossil fuelled to electric cars.

## Activity 3

15 minutes

A petrol car built in 2014 has a fuel consumption of 55 miles per gallon and meets the Euro 6 standards for NOx emissions. It is running on petrol with no added biofuel which has an emission factor of 2.3 kg CO2 per litre.

1. Express the fuel consumption in litres per 100 km.
2. The car is being used on a trip of 300 km. Calculate the quantity of CO2 emitted in kilograms.
3. What is the maximum amount of NOx that it is permitted to emit over 300 km?

(A text entry box would appear here, but your browser does not support it.)

### Answer

1. If the fuel consumption is 55 miles per gallon:

   Litres per 100 km = 283 / 55 miles per gallon

   = 5.145 litres per 100 km

2. Fuel consumption over 300 km = 3 × 5.145 = 15.44 litres

   CO2 emitted = 15.44 litres × 2.3 kg per litre = 35.5 kg

3. From Table 3 in Section 5.2, the maximum NOx emissions under the Euro 6 standard are 0.06 grams per km.

   So maximum permitted emissions over 300 km

   = 300 km × 0.06 g per km = 18 g

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