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Wolfsburg, 03 November 2017

Nearer to real life

A new standard for realistic consumption figures is made possible by sophisticated measurement systems.

Maurizio Gualato accelerates. The 26-year-old from Wolfsburg brakes and shifts up and down through the gears in accordance with his instructions. Again and again, in an extremely concentrated way. In half an hour, his silver Volkswagen Arteon has clocked up precisely 23.30 kilometers. But Gualato has not moved from the spot.

During the entire drive, the young quality tester and the vehicle remained on the roller dynamometer in Hall 79 in Wolfsburg. On 21 dynamometers, the specialists are accomplishing a minor revolution. They are measuring how much fuel Volkswagen's new models actually use. And they are following the new European standard WLTP, which has only been in force for a few weeks.

All catalog consumption figures to be realistic

This new standard tackles an issue that has annoyed many people for a long time. To date, consumption figures in catalogs have been significantly lower than the values actually experienced by customers. The reason is the legal requirements on which manufacturers' measurements have been based. The old NEDC (New European Driving Cycle) consisted of a program completed on the dynamometer and it had not been changed since 1992.

However, the driving behavior simulated during the test was very far removed from actual driving conditions. For example, the engine was operated at idling speed for more than a quarter of the time and the maximum speed travelled never exceeded 120 kilometers per hour. These values measured on the basis of NEDC were those which were published in manufacturers' catalogs.

Since September 1, 2017, fuel consumption figures in Germany have been subject to a new standard – WLTP. The abbreviation stands for "Worldwide Harmonized Light Vehicles Test Procedure". The objective is to determine the fuel consumption of new vehicles in a way which is both realistic and comparable – between different brands and models. For manufacturers like Volkswagen, the new standard means considerable changes at many levels and in many departments.

Overtime on the roller dynamometer

Customers will also need to get used to the change as the WLTP figures will be higher than those previously published. On the other hand, they will mean greater clarity for customers. "The driving profile reflects actual driving," says Christoph Kohnen, Head of Emissions and Consumption Legislation at Volkswagen. For this purpose, a procedure was developed over many years across national boundaries and the result is a document which is hundreds of pages long. The change is to be implemented in stages and the full WLPT program will come into force in September 2018.

In Hall 79, slightly to the north of the main plant in Wolfsburg, the change has brought with it many hours of additional work. "In future, we will measure a separate consumption value for each engine/transmission combination," explains  Jan Dössing, who is responsible for the WLTP project. This is why Maurizio Gualato and his colleagues are repeating the defined driving program almost round the clock. "Every day, we run 250 tests here," Richard Preuß, Head of Roller Dynamometers, reports.

That means about 55,000 tests per year – and there will probably be even more. Under the WLTP regulations, the effects of vehicle equipment also need to be measured. This includes low-rolling-resistance tires or wide 18-inch wheels, air conditioning and sunroofs. Such additional equipment can make a difference to fuel consumption. Although drivers are well aware of this fact, such figures have not been included in the published figures to date. In future they are to be taken into consideration in determining fuel consumption.


Software to consider the effects of special equipment

"We have about 300 different part numbers for aerodynamically relevant components we need to take into consideration," says Dössing, explaining the complexity of the task in hand. This is why it is impossible to test all possible combinations for each engine option. For the Golf alone, there are a huge number of possibilities of combining equipment and technology. This is why Volkswagen has developed a dedicated IT solution. The software knows the effects of individual equipment items on consumption and combines them with measured values from the test rig.

Although this solution may sound simple, it is actually extremely complex. "On the online configurator, the figures are presented on a real-time basis," Wolfgang Frank reports enthusiastically. He is responsible for the WLTP project from the sales side. Whenever customers configure their model on their computer or in a dealership, the precise consumption for this configuration is determined on the basis of WLTP. This means that customers have the information they need to decide whether to order wide tires, with higher consumption, or rather to take a smaller engine.

Such questions are likely to become more important as road tax is calculated on the basis of fuel consumption. To date, the calculation has been made generally for a specific model, irrespective of its weight or equipment. In contrast, WLTP allows the calculation of consumption figures for an individual car on which the road tax can then be based. Volkswagen is currently introducing this method for the up! GTI, the brand's latest model. The new procedure is transparent and applies to all manufacturers.

Measurements to be made on the road in future

In addition to fuel consumption, the new standard also regulates the quantity of pollutants released into the environment. New vehicles must meet these limits not only in the laboratory but also in everyday operation. This is why the test team from Hall 79 has been implementing a further innovation, RDE (Real Driving Emissions) tests since September.

For this purpose, they regularly attach mobile measuring equipment to vehicles.

Kraftstoffverbrauch Golf TDI 110 kW / 150 PS in l/100 km: kombiniert 4,3-4,2 / innerorts 5,1-5,0 / außerorts 3,8-3,7; CO2-Emission kombiniert in g/km: 111-109; Effizienzklasse: A.

The yellow box on the rear of the car registers the quantity of nitrogen oxide and particulates emerging from the exhaust. During the test, the car is driven over cross-country routes and highways as well as in the city for about two hours.

Currently, the emissions measured during these real-life tests are allowed to be about twice as high as those measured on the dynamometer. By 2020, emissions on the test rig and during the RDE tests on the road must be identical subject to a certain test tolerance.

Of course, every trip is different and every driver has his or her own driving behavior. This means that the RDE results are not comparable with each other. Nevertheless, the car must comply with the emission limits during each trip. This is also monitored by independent inspection agencies such as TÜV. Inspectors from the agency regularly visit Hall 79 and monitor the test results.

During these tests, Volkswagen performs outstandingly well in comparison with its competitors. In the eco-test carried out by German motoring association ADAC, the diesel models with Euro-6 engines emitted an average of 146 milligrams of nitrogen oxides per kilometer. Almost all the other manufacturers recorded poorer values.

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