The NEDC tricks of the car manufacturers

The Exhaust scandal around the diesel engines from Volkswagen is currently the absolute hot topic in the automotive industry and among drivers. Unfortunately, many articles deal with the manipulation of exhaust gas values ​​in a very undifferentiated manner in dealing with the entire subject of “consumption values”. The “fraud” on the emission values ​​in the USA has absolutely nothing to do with the discrepancies between “real consumption” and “test bench consumption according to NEDC standard”. Unfortunately, too many authors of “scandalous articles about the auto industry” understand little or nothing about the subject of the NEDC standard.

The Volkswagen fraud

What Volkswagen did in the US is simply fraud. Using software that detects test bench runs and then puts the engine into economy mode is fraud. And because there are no two opinions on this, those responsible admitted that relatively early on. Volkswagen now has to deal with the consequences. But an entire auto industry is also under general suspicion and the pseudo-argument comes all too quickly: "Of course - that's what all manufacturers do, because no car reaches it in everyday life standardized NEDC value".

NEDC - norm and the permitted “fraud”

Even if the calls for a “realistic” consumption measurement are not unfounded. The tricks used by automobile manufacturers to reduce standard consumption when taking measurements according to the NEDC are legal. So far, the suspicion that other manufacturers are deliberately manipulating the measured values ​​using a “defeat software device” has not been confirmed. But why do the prospectus consumption values ​​differ so far from the everyday life of many automobile drivers?

NEDC cycle and everyday life

In order to make a comparison between the cars, one had to agree on a “norm”. The "New European driving cycle”Has been describing how cars are measured for“ efficiency ”since 1997. However, the route driven in the NEDC is rarely the route that you drive yourself (Read NEDC cycle). But that is just one reason, the other reason is the quite legal trickery that was allowed in fixing the NEDC to automobile manufacturers.

mein-auto-blog explains 5 “legal” NEDC tricks

1. Deactivate alternator | The test only takes 20 minutes and runs over a distance of 11 kilometers. This route can be driven with a simple battery charge, no alternator is used to generate electricity. And so the manufacturers in the NEDC are allowed to dismantle the alternator. Less “load” and resistance for the motor increases the efficiency. In addition, the original car batteries can be exchanged for smaller batteries.
2. No electrical consumers | Electric windows, dipped lights, radio and multimedia systems. All this consumes electricity. Electricity, which in turn must be generated by the alternator. However, the manufacturer can go into the NEDC standardization without dipped beam, without activating the air conditioning system or other electrical consumption. This also increases efficiency.
3. Engine oil | Special low-viscosity oils are permitted for the test bench. These engine oils do not have to correspond to the production status and can thus increase the efficiency of the engine again. Less resistance, faster reaching of the optimal temperature. What would not be possible in a series vehicle can be used on the test bench.
4. Suspension | Optimum handling is not important on a stationary chassis dynamometer. Therefore, the settings of the lane, camber, spread and caster of the axles can be optimized so that a minimum rolling resistance is achieved. In everyday life, these settings might be completely impassable! In addition, the air pressure of the tires may be increased. This also reduces rolling resistance, but could be a safety issue in everyday life. And while the brake linings are always light in the production car, the pressure of the linings on the discs can be minimized for the test bench run.
5. Body | To determine the “driving resistances”, the vehicle is checked on the “road”. The determined data are used for the test bench run. The NEDC allows manufacturers to manipulate the vehicle's aerodynamics in order to determine the “driving resistances”. For example, gaps in the body are masked, special hubcaps and narrow wheels are also allowed. This lowers the air resistance and lowers the "driving resistance" for the test bench run

No chance for Otto-Normalo?

In everyday life you will neither drive a standardized 11 km route nor spend 20 minutes on the road. You will still be standing exactly 25% of the time. Because these are the facts about the NEDC. And because of the possible 1/4 standstill, the start-stop systems have also become standard in recent years. If a quarter of the cycle consists of “standstill”, the automatic start-stop function is more or less mandatory. But check out how much you “stand” on your daily route.

You can use special low-viscosity oils for your car in everyday life, there are recommendations from the oil industry, but you will have to consider other limits for the care of the vehicle, as this is important for standardization.

You should also not set the axle settings to “minimum” rolling resistance, but to “maximum” safety. And when it comes to tire pressure, 0.2 bar is usually justifiable - the “optimization” for the NEDC, however, is significantly higher.

All of this explains why only a few drivers really achieve the prospectus value in everyday life. We on mein-auto-blog also drive a "Consumption drive ”and orientate ourselves on our very own system.

For the future, however, there is a new “cycle”. The WLTP is to replace the NEDC, the goal is clear: More realism. 

With the WLTP and a permitted check of the values ​​on the road with series vehicles, the “trickery” of the manufacturers is to be put to an end. One should not forget, however, that the manufacturers' tricks have so far been completely legal - the legislature has allowed that.