Dieselgate Questions & Answers: All you need to know about the VW scandal

German car manufacturer VW is being investigated by EPA over claims of emissions test manipulation in 482,000 diesel cars. This is achieved through the use of cheat software, which recognises when the car is performing an emissions test. The investigation is a disaster for the company. We explain how VW has been cheating these tests, which cars are affected, how the authorities caught VW, what NOx are and what measures are being taken against Volkswagen.

How did the VW emissions scandal begin?

The Californian Air Resource Board (CARB) and the Environmental Protection Agency (EPA) became suspicious back in May 2014 when tests on a VW Jetta and a VW Passat registered emissions readings far above the expected values. The Nitrous oxide readings were particularly high; readings were up to 40 times higher than the permitted limits.

When confronted with the results, VW dismissed these cases as anomalies and stated that various technological and usage factors could explain the readings. After a voluntary recall by VW, EPA carried out new tests in December 2014. Once again, extreme discrepancies between dyno test and road test results were discovered. Only after EPA threatened VW with sales bans for these models as of 2016 did the German motoring company reveal the truth; special software, designed to recognise tests and deactivate emission controls in the exhaust system, had been installed.

EPA has thusly accused Volkswagen of violating the US Climate Bill, and is demanding the recall of 482,000 diesel vehicles in California, in addition to fines of $37,500 per car, or 18 billion US dollars in total.

How are exhaust emissions tested?

In Germany, dynamometer (rolling road) emissions tests must be carried out in accordance with ECE Standard R83. The current handbook for carrying out NEDC (New European Driving Cycle) consumption & emissions testing cover 56 pages of densely packed text. Even with such detailed rules and regulations, car producers still have many fully legal options with which they can influence test results for their own benefit.

The influence of computer controlled motor management today is perhaps best demonstrated by the changes in the legally required emissions testing every car must pass. Only a few years ago, cars were hooked up to tubes and pipes in order to examine the exhaust gases for CO and CO2 levels. Nowadays, the examiner merely has to connect to the OBD II on-board diagnosis system; the software will display all relevant information: lambda sensor function, catalytic converter effectiveness, potential engine misfires, as well as data from the secondary air system, the turbocharger, etc. The modern emissions test is therefore more of a data inspection than anything. The engine control system that compiles this data is encoded; the system itself cannot be viewed by the examiner.

What “legal” options for the manipulation of emissions and consumption testing do manufacturers have?

The standard lab testing cycle has been known for years, giving manufacturers loopholes through which they can optimise their efficiency and emissions for the test rig. This can be achieved by turning off energy sapping equipment such the air conditioning; adapting the charging cycle of the alternator; eliminating temperature differences; using a cold air supply; or eliminating certain load conditions.

This affects both the behaviour of exhaust gases and fuel consumption. The consumption testing that new cars are put through clearly demonstrates the weakness of the standard test. In Germany for example, an unrealistic speed limit of 120 km/h is prescribed for rolling road testing.

In 2007, an auto motor und sport reporter stated “If you look closely at the NEDC road simulation profile, it is immediately apparent how far removed it is from reality. [...] The car completed a total route of 11.007 km at an average speed of 33.6 km/h. [...] It is for this reason that auto motor und sport performs its own efficiency testing for every test car, covering a total distance of approximately 2,500 km.über eine Gesamtstrecke von rund 2.500 Kilometern."

Further tests by auto motor und sport demonstrated differences of approximately 25% between lab-tested consumption and true consumption. In 71% of all vehicles tested, real-world fuel consumption was higher than that achieved during NEDC testing.

How does Volkswagen’s manipulation work?

As if all the legal loopholes weren’t enough, the VW models in question are also equipped with software that manipulates the results. The electronic motor control system is able to recognise that it is being tested through markers such as the position of the accelerator pedal and the fixed position of the steering wheel. The car then reduces the amount of diesel injected, increases the amount of air in each combustion stroke, and perhaps also alters the timing of each injection in order to optimise emissions readings. As load and comfort requirements are virtually non-existent on the dyno, the manufacturer doesn’t have to take power or performance into account.

Test recognition - legal or illegal?

One hotly debated aspect of the VW manipulation scandal is whether it is acceptable that cars recognise test conditions. Is it permitted, or is it forbidden? Vincenco Lucá of German testing body TÜV-Süd is clear in his response. “The car must be able to enter a ‘test mode’; this is necessary in order to switch off systems such as adaptive cruise control, ESP, ABS, and the activation of four wheel drive systems. This all goes to ensure safety during testing.

However, and this is the focus of the current discussion, whilst driver assistance systems may be deactivated, the engine control system may under no circumstances be tampered with. Changes to engine mapping are prohibited. In simple terms, only one engine mapping profile is permitted. This is the issue with the affected VW engines; they are fitted with a special program that recognises emissions tests and activates a separate engine mapping profile.

How was VW’s deception discovered?

The International Council on Clean Transportation (ICCT) had already provided results from comprehensive real-world road testing back in 2014. The tests were to demonstrate discrepancies between dyno and road test results, if any. The differences were enormous. There were vehicles that performed even worse than Volkswagen’s models.

Of all people, it was a German that set the ball rolling that eventually became the catastrophic avalanche for Volkswagen and the German motoring industry we see today. The ICCT’s Peter Mock suggested that the US versions of German diesel vehicles be tested. “The goal was to demonstrate that German cars in the US are cleaner than their European counterparts, as the standards in the US are stricter.” Mock told Manager-Magazin Online in an interview.

After VW models repeatedly demonstrated large discrepancies between emissions tests carried out on the dynamometer and on the road, experts became suspicious. They dramatically changed the dyno test cycle and combined two partial cycles into one. In this test, the VW diesels were proven to produce extremely high emissions, especially Nitrous oxides (NOx). The software didn’t recognise the new cycle as a rolling road test, and instead the standard engine mapping was used, in which the engine control system focuses on performance and efficiency, with little regard for emissions.

What are Nitrous oxides (NOx)?

NOx, or Nitrous oxide, is the collective name for molecular compounds composed of Nitrogen and Oxygen atoms. The two most important types are Nitrogen Monoxide (NO) and Nitrogen Dioxide (NO2).

Nitrogen oxides belong to a group of reactive Nitrogen compounds that can cause environmental damage in many different ways. Together with volatile hydrocarbons, Nitrogen oxides are responsible for the summer increases in ozone formation and also contribute to fine dust pollution, according to the Federal Environment Agency.

The effects of NOx are especially problematic for Asthma sufferers; higher concentrations can lead to bronchial constriction. Nitrogen Dioxide is particularly toxic to plants; effects range from necrosis (where the leaves turn yellow), to premature aging and stunted growth. Dissolved, Nitrogen Dioxide also contributes to soil over-fertilisation and acidification. This is also an issue in bodies of water.

How can NOx emissions be reduced?

There are three main methods to reduce NOx emissions from diesel engines to accepted levels: Exhaust gas recycling, NOx storage traps, and SCR (Selective Catalytic Reduction). The optimisation of turbo- and superchargers and injection timings can also help in reducing emissions.

A NOx storage trap works by trapping Nitrous oxide molecules on a surface in the exhaust system, most commonly made of a Barium compound. When the trap is full, the Nitrous oxides are converted into harmless Nitrogen (N2) and non-toxic Carbon Dioxide (CO2). Carbon Monoxide and Hydrocarbons from the exhaust gases act as reductants.

SCRs require ammonia (NH3), which is stored in an additional tank as an aqueous solution (AdBlue) and injected into the combustion process. This causes a chemical reaction, the products of which are water (H2O) and Nitrogen (N2).

Which VW models are affected by the current emissions scandal?

The US models in question (Golf, Jetta, Passat, Beetle, Audi A3) are all fitted with the EA 189 2.0 litre TDI motor, which is used across the entire Volkswagen group in many different models. In order to reduce emissions, this engine uses an NOx storage trap. The Passat is furthermore fitted with SCR. Although the readings from the Passat were better than those taken from the other models, emissions were still many times higher than the permitted levels.

Volkswagen has now admitted that this cheat software can be found in 11 million cars with this motor. The majority of these motors will be unaffected by the inclusion of the software, according to VW.

Why are the tests themselves part of the problem?

Rolling road tests make standards replicable, and results reproducible. Laboratory conditions are the same for all manufacturers, and make the results comparable. Manufacturers can therefore orientate themselves better to market benchmarks and legal limits. But, as with all tests and examinations, well-prepared examinees fulfil the tested parameters exclusively. That is to say, the development of exhaust technology is not focused on producing the lowest amount of dangerous emissions possible, but rather cars that can pass the tests. More is made of consumer-relevant factors as efficiency, performance and comfort. None of this can be held against car manufacturers; they are operating entirely within the legal limits.

That isn’t the case with VW. The 2.0 litre TDI doesn’t achieve the legal standards; only with the help of the cheat software can the motor manage this. Volkswagen crossed the line between optimising engine control to pass the test and fraud. This was achieved using special software installed specifically to complete the test cycle. Essentially, the cars driving on the road are different beasts to those completing the test.

One problem is that all cars demonstrate significantly worse emissions readings on the road. This issue was recognised by the Baden-Württemberg State Institution for Environment, Measurement and Conservation (LBUW) back in April 2014. Real-world road testing showed that the average NOx emissions of EU6 diesel engines were up to eight times higher than the legal limits. To compare: The VW diesels exCee’ded US legal limits by a factor of 40.

Environmental agencies have been demanding for years that mobile testing become the standard form of testing; after all, air pollution isn’t created in the lab, rather on the road.

Do other brands employ such illegal test manipulation measures?

Christof Gauss, Head of Automobile Testing at the ADAC Test Centre in Landsberg, makes his point clear. “We cannot rule out that other companies are using these cheats, even in Germany.” Previous real-world tests performed by ADAC demonstrated excesses of 300 - 700% over legal limits. Even the Volkswagen CC, currently undergoing long-term emissions testing, produces excessive NOx despite the regular activation of its SRC system.

Gauss is another expert that voices approval for Portable Emission Measuring Systems (PEMS) in order to monitor pollutants in real-world situations.

What does Dieselgate mean for VW?

Volkswagen now faces a catastrophe of its own creation, of which the scale constantly increases. The threat of fines of up to $18 billion is currently the least of its worries. Just through the drop in share price, the company has lost over $27 billion in value since 18th September. The share price of subsidiary company Porsche has also dropped by more than 30%. The first compensation claims from shareholders have started arriving too.

The US Ministry of Justice has also commenced criminal investigations against VW, personally addressed towards managers of the multinational. Furthermore, the first class-action lawsuit was filed on the 18th September by VW customers, claiming that the affected cars have lost thousands in value. The German Transport Minister has called for VW cars to be emissions tested by an independent body, and the EU has announced it will be taking a particular interest in emissions values of the entire automobile industry.

What does the VW emissions scandal mean for the diesel?

According to Christof Gauss, Head of Automobile Testing at the ACAC Test Centre in Landsberg, the diesel will continue to have a future, despite the current issues with emissions limits. He explains that HGVs face very strict NOx testing, however thanks to the use of SCR systems, legal limits are only exCee’ded by up to a factor of 1.5 when road tested as opposed to lab tested.

Florian Flaig, Spokesman for Bosch, is also certain of the diesel’s future. “Thanks to its efficiency, the diesel will continue to be a valuable tool in the fight to curb CO2 emissions.” The technology to ensure legal limits are also adhered to in real-world usage already exists. The ICCT tests (International Council on Clean Transportation), which provide the basis for the US tests that the VW models failed, have proven that this technology works: the BMW X5 performs especially well in real-world ICCT testing.

Emissions limits may however continue to prove a problem for diesel cars, especially in the USA. EU6 allows 80 mg of NOx emissions per kilometre, whereas the legal limit in California is only half of this. Highly compressed engines such as the diesel, which produce high amounts of Nitrous oxides are rarer in America. Some interpret the strict limits imposed on this type of engine as a policy to benefit domestic manufacturers, who flood the market with vehicles powered by giant petrol engines that burn through oceans of fuel and thereby emit especially high amounts of CO2. Conversely, on the other side of the Atlantic, European CO2 limits are becoming ever stricter. The frugal diesel engine is therefore especially popular there. But the automobile industry would be well-advised to dramatically reduce NOx emissions of these engines; the link to fine dust pollution in cities has been proven time and time again.

It is this fact that could facilitate the breakthrough of concepts such as plug-in hybrids and electric cars in the not too distant future. After all, they are the more expedient option, in terms of the future. Burning fossil fuels not only produces noxious gases, but also masses of CO2. This could be avoided by using renewable energy sources to provide the electricity for our vehicles.

It is entirely possible that we will look back on this episode in 20 years, not as the beginning of the end of the diesel, but rather the combustion engine in general.


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3 October 2015
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