WLTP vs NEDC - "Commuter cycle vs unworldly"

What do our cars use?

What a car consumes is stated in the brochure and is an important criterion for many car buyers when purchasing a new car. The higher the consumption, the higher the CO2 emissions. The environmental conscience and the wallet, both demand low consumption values. But what if the prospectus value and everyday life are far apart?

Automobile magazines and TV programs have repeatedly made the “unfamiliar” calculation of consumption according to the NEDC and the sometimes absurdly high deviations in everyday life an issue. And the criticism is justified. Also here in the blog, the NEDC value is criticized as a “laboratory value”. On autohub.de, for example, the consumption value of the test vehicles is not determined in the laboratory, but on the road, and instead of a single driver profile, we have adopted three profiles. (For more information on the “my-auto-blog three-type method” click) 

Nevertheless, the NEDC standard value is currently valid and the consumption and emission values ​​determined from it form the basis for the EU's CO2 fleet consumption targets. A test cycle was mapped within the NEDC that enables comparability between the vehicles, but does not provide enough information for daily operation due to the test cycle. The test cycle accelerates several times to 13 km / h within approx. 50 minutes, with a time interval of up to 26 seconds available. Which is already completely out of place. The maximum driven speed is 120 km / h and is only reached once and for a few seconds. In addition, in a 2013 study published by the “T&E” showed how the automobile manufacturers “cheat” or at least could cheat in the certification of standard consumption.

For example, the battery is not recharged during the 20 minutes in the cycle, the wheel geometry is optimized for less rolling resistance, the tire air pressure is set even higher than necessary on a roller dynamometer, the vehicle is always the absolute basic model and therefore particularly light, 4 % Test tolerance are deducted and T&E also speaks of optimized engine control units.

The consumer is disappointed

The result is a massive deception by the consumer. Of course, one could say: No, the consumer only has to drive the car as he does during the NEDC test cycle, and the result is just right. Oh yes, and of course he shouldn't order any special equipment, leave out the air conditioning and lights and please increase the tire pressure to a dangerous maximum.

Test vs. reality

The non-global test standard (NEDC) is purely a laboratory size. The manufacturers also optimize the test vehicles. On the verge of legality, the standard specifications are optimized, everyday life remains locked out. This development has led to a growing consumer desire for an “honest” and reliable test standard.

What will my car use later? Which car do I drive cheaper? What kind of drive really suits my needs?

The new cycle: WLTP - the commuter consumption measurement!

In March 2014 the UN approved the new “globally” valid test cycle WLTP. Instead of various procedures in the EU, Asia, North America and China, the WLTP is intended to ensure global standardization of the measurement procedure. Only the USA are not yet available for the cycle. So wait there. In the end, there would be two test standards left. But the USA will probably also be added.

Compared to the NEDC, in which almost 20 minutes of downtime were included in the 25 minutes test cycle, the new WLTP is not only run for 30 minutes, but also the downtime (traffic light simulation in city traffic) is reduced to 13%. While the NEDC was driven on 11 km, the WLTP covers good 23 kilometers.

The average speed in the NEDC was 34 km / h, with the new WLTP 46.6 km / h. In addition, the special equipment is taken into account and the switching times are no longer fixed by the cycle, but are determined according to the optimal conditions. The WLTP in its test form is therefore now much more dynamic than the NEDC and the fear of the automobile manufacturers is great. Because these changes sound like “additional consumption”.

But that was the goal, wasn't it? If you want to determine a more realistic “standard value” and the NEDC has always been far too low, then the WLTP would have to offer a decent surcharge.

Danger for the 95 gram fleet specification of the automotive industry

Now, of course, automobile manufacturers are afraid. Fear of the new measurements, fear of being run over by the CO2 agreement on fleet consumption. Fear of having pushed technical optimization to the norm for nothing. What if downsizing and start-stop systems suddenly no longer play a role? Entire engine generations and transmission variants have only just been optimized to meet the NEDC standard.

Anyone who knows the development cycles of the automotive industry understands. If the WLTP is really to be implemented up to 2017 and should be binding as of 2018, then the automotive industry faces major tasks. What 2018 is supposed to bring to the market is already doing test rounds in pre-development.

Not least thanks to an initiative by VDA the solution could now look like this: For a transitional period, the NEDC will remain the measurement method for the certification of new automobiles and thus the unfamiliar basis for determining emissions and the WLTP will be introduced for the end customer as a “more realistic” consumption figure and as a “label value” on the Glued car. Double work. Half as useful?

But is the WLTP more realistic than the NEDC?

If you look at the test cycle, you will find the test scenario to be more extensive and thus felt to be more realistic. TÜV SÜD has now published interesting findings in a workshop on NEDC and WLTP:

"Under consumption in the WLTP"

A Mercedes-Benz C250 CDI consumed 6.78 liters of diesel per 100 km during the WLTP cycle in the modern test center in Pfungstadt. The same vehicle in the same test center under the same conditions had used 7.18 liters in the NEDC cycle the day before.

One could say that it is due to the powerful diesel engine and the manual gearbox, here you can simply drive particularly efficiently in the new WLTP cycle. Because dozens of parameters are recorded for the WLTP, including the cheapest switching points. Instead of the fixed shift specification in the NEDC, the gears can be freely determined in the WLTP.

An isolated case? No. An additionally tested Mercedes-Benz C180 CGI was driven twice in the NEDC and measured with 8.18 and 8.16 liters and the next day with 7.37 and 7.49 liters in the WLTP.

NEDC TÜV discrepancy vs. NEDC type approval

Both the C250 CDI and the C180 CGI were vehicles of the W204 series and not up to date. In addition, both vehicles were tested under “standard” conditions. The fact that the WLTP cycle produced lower values ​​than the NEDC standard is due to the new procedure. The route is similar to a typical commuter route and the longer test duration optimizes the operating condition of the vehicle towards the end.

Even in the three-type methods, we always have vehicles that fall below the NEDC value in the eco-test or at least come very close. However, this only seems to apply to manual transmissions and motors with a balanced range of services.

Isn't the new WLTP cycle even a help for the automotive industry now?

After the test at TÜV SÜD in Pfungstadt, one could get the impression that the WLTP does not help the consumer, but the automotive industry. So why balk at implementation on their side?

And what does the consumer benefit from? It looks like the consumer is stupid again. It also looks as if the WLTP is now a dynamic driving cycle - and if you go to exactly this cycle every day to get to work and then take all the savings tips to heart, you will also achieve the standard values ​​- but if the WLTP- Standard consumption is really below the previous NEDC value, then it becomes even more unrealistic for many consumers.


NEDC WLTP? Control is necessary!

The NEDC value of the C180 CGI determined by TÜV-SÜD is 8.16 liters, almost 1.5 liters above the NEDC standard consumption from the original type test of the vehicle. Here the tested Mercedes-Benz C180 CGI was specified with 6.7 liters.

These differences - a comprehensible explanation could not be provided - leave an automotive blogger at a loss for the time being. One thing is certain, however: the WLTP does not help the consumer any more than the NEDC has done so far. You will still not be able to read from a brochure what our cars really consume in everyday life!







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