Mercedes is the first premium manufacturer which announced that all its passenger car portfolio will gradually switch to WLTP (Worldwide Harmonized Light Vehicles Test Procedure) until autumn 2018.
The current NEDC cycle test is very old, dating since 1992 and involve traffic situations which are very far from today conditions. The accelerations are very gentle and the procedure itself favorize the modern turbo direct injection engines.
Because the turbo enter in function very rare along the cycle, the results are exceptionally low, very far from the real traffic. Many independent tests has proven that the difference between real consumption and official consumption goes to up to 45% in case of turbo engines while the gap is smaller for the classical aspirated engines.
The introduction of the WLTP can be compared to a currency reform as far as the customer relevant CO2 and consumption values are concerned. From September 2018, the vehicles will be measured by new standards.
The differences between NEDC cycle and WLTP cycle
- The WLTP driving cycle has a length of around 23 km, more than twice as long as the 11 kilometers of the NEDC.
- The WLTP driving cycle will take 30 minutes, 10 minutes longer than the NEDC cycle and has only 13% of standing while NEDC has 23.7%
- The WLTP will have an average speed of 46 km/h instead of only 34 km/h for the NEDC.
- The maximum speed will reach 131 km/h for the new WLTP cycle compared with 120 km/h for the NEDC.
- The WLTP cycle itself is more tough, with harder and more frequent accelerations like you in the graphic below.
In addition, a road test the so-called RDE (Real Driving Emissions) test is used to verify that the Euro 6 limits for nitrogen oxides and particulate number are not exceeded after conformity factors are taken into consideration.
Unhappily, the goal of global harmonisation was not fully achieved. The new WLTP cycle apllies in the EU, UK, Norway, Iceland, Switzerland, Lichtenstein, Turkey and Israel.
Japan use a modified form of the WLTP while South Korea will use the WLTP for diesel engines.
Russia, Australia, Asia and South America will keep the NEDC procedure, while USA and Brazil has other standards.
The new Mercedes CLS will be the first Mercedes to be certified according to WLTP under the Euro 6d-TEMP emission standard. This standard involve also the RDE test.