More realism in consumption

Stuttgart, 30. January 2018

This theme is a classic in the Stammtisch-discussion: Are the factory consumption of new cars is realistic? In the last years, information with a One before the decimal point with thick Plug have sown-in hybrid cars, massive doubt, as mythical values for some of the downsized petrol engine. Now, a new test cycle is intended to provide more realistic results. The WLTP is the magic word. What is behind it?

Old vehicles, new currency

Mercedes brings with it as a quite accurate picture of a "currency reform" to the game: The vehicles don't change, they can only be measured according to the new requirements. But let's see: In 1992, the "New European driving was introduced in cycle", in short, NEDC,. Of course people thought back then not to Plug-in Hybrids, and Downsizing-burners, of which the engineers took advantage of in the past few years, the weaknesses of the NEDC in your favor. The development of the WLTP began in 2007 with the objective to define, on the Basis of realistic driving data, a far, far valid test cycle. The sounds even today, in the full WLTP-name: Worldwide Harmonized Light Vehicles Test Procedure.

No globalisation at the point of consumption

Unfortunately, the goal of a world was not achieved-cycle. Europe, including Turkey and Israel take advantage of the WLTP, Japan takes it in a modified Form, South Korea for diesel vehicles. Russia, many countries in the Middle East and Asia as well as South America and Australia remain in the NEDC, the USA, Brazil and other countries have their own cycles. After all, China used for the latest emission stage, the WLTP test procedure for the consumption, Beijing is planning its own solution.

Measurement, with more reference to Everyday life

What are the changes in the WLTP cycle specifically, compared to the previous NEDC measurement? The driving profile is in the WLTP clearer, more dynamic, with larger speed changes. The NEDC has a high proportion of trips with a constant Tempo (40 percent) and comparatively little speeding (21 percent). The WTLP knows, however, four distinct phases: up to 60, to 80, to 100, and of up to 131 km/h. (In the NEDC was at 120 km/h.) So city to Interurban, and highway driving are simulated. The Specifications are close: for example, the outside temperature could be in the NEDC is between 20 and 30 degrees, 23 degrees are prescribed in Europe, in addition to 14 degrees.

No Plug-in loophole?

At over 700 pages, the procedure for the certification declares to the WLTP, including more realistic targets for cars with Plug-in Hybrid. Because these are externally charged, driving these models to the Test several times. Is started with full battery. The cycle is repeated until the battery is empty. Subsequently, a measurement with empty battery, wherein only the internal combustion engine and regenerative braking is active. From these two measurements, the expense to be recognized is calculated at the end of the CO2 value by the two results will be dependent on the electric range set into the relationship. Whether this will have significantly changed consumption information, but it must show in the near future. And one more interesting aspect of the WLTP: It is not tested only the basic version of the model, but also special equipment is taken into account.

Up to 20 percent more fuel consumption

How high is the difference between WLTP and the NEDC is illustrated by the example of the VW Up GTI. According to the old cycle it comes to an average consumption of 4.8 liters and 110 grams of CO2, it is 5.7 liters or 129 grams. Here are 17.3 percent more. Until the fall of 2018 Mercedes wants to change his Cars program on WLTP data. According to the Association of the German automotive industry, the fuel consumption and CO2 information in the Mediterranean will rise by around 20 percent. This is also likely to have an impact on the CO2-based Vehicle tax, here we will examine the consequences from September 2018. The fleet goal of legislation in Europe, however, is only changed to calendar year 2021 to WLTP.

RDE: more Realistic exhaust gas measurement

In times of diesel scandals and the consumer, of course, also on the emissions. Especially sharp the emission standard Euro6d-TEMP. To certify a model with new or modified engine for this purpose, in addition to the WLTP is still the RDE Test (Real Driving Emissions). You mean: in Addition to the measurement in the laboratory, the vehicles are equipped with a "test box" at the rear. Analyses of the content of carbon monoxide, oxides of nitrogen (NOx) and the particle number. Added to this are parameters such as weather and GPS data. The driving cycle is not fixed, but there are many edge conditions: The vehicles will be moved between 90 and 120 minutes on public roads, one third of the urban, extra-urban and on the highway. For the city of an average speed between 15 and 30 km/h is provided, at highway speeds of 90 and 110, but not faster than 145 km/h to be driven. The outside temperature must be between 0 and 30 °C, the air conditioning is turned on. The test drive should not be more than 700 meters above the sea and only 100 meters difference in altitude. RDE is valid for new Emission types since September 2017 and for all new registrations (regardless of how long the model is already on the market) starting in September 2019.(rh)