Driving cycle

A driving cycle defines under which conditions and with which speed sequences a vehicle is operated when determining energy consumption or fuel consumption and CO ₂ emissions in vehicles with internal combustion engines. This is part of the manufacturer's information for the approval and sale of the vehicles.

General

For a driving cycle, boundary conditions such as starting temperature, switching points (only vehicles with manual transmission), vehicle preparation (conditioning), payload, start of emission measurement and more are specified. Driving cycles should produce a load that is as realistic as possible, this being an average profile. The driving cycle is usually carried out on an engine or roller test bench. This enables reproducible and comparable results to be obtained. From the manufacturer's point of view, such a driving cycle offers development security.

The driving cycle is also relevant for performing diagnostics . It is an essential part of an exhaust gas regulation .

NEDC, Directive 70/220 / EEC

Measurements under the New European Driving Cycle (NEDC), Directive 70/220 / EEC ( english New European Driving Cycle (NEDC) ) are carried out in accordance with Directive ECE R one hundred and first This guideline applies to vehicles with internal combustion engines, electric hybrid drives and all-electric vehicles.

At the end of the 1960s , under a rapidly growing motorization, the first exhaust gas limit values were required, first in Germany and then in France, which led to the common directive 70/220 / EEC of March 1970.

In 1976, the first oil crisis was followed by a method of the United Nations Economic Commission for Europe for measuring fuel consumption , which became the basis of DIN standard 70030 in 1978, according to which a driving cycle simulated city traffic and also constant speeds of 90 km / h and 120 km / h were driven on a roller dynamometer. Before the third mix, measurements were made according to DIN 70020 without a driving cycle at only one speed.

New European Driving Cycle (NEDC) 1992–2017

With Euro 1 from July 1992, the driving cycle of Directive 70/220 / EEC was extended beyond city traffic. The European Commission (EC) is advised by a body called the Motor Vehicle Emissions Group (MVEG). The extended operating cycle is New European Driving Cycle called (NEDC), English New European Driving Cycle (NEDC).

Since 1997, the fuel consumption has to be calculated from the exhaust gas quantity, which is determined in the driving cycle of the exhaust gas standard. The resulting fuel consumption figures were around 8% higher than the third mix. With the Euro 3 emissions standard , the New European Driving Cycle was transformed into the Modified New European Driving Cycle (MNEFZ), in which the measurement begins immediately after a cold start at around 25 ° C , not after 40 seconds as before.

In June 2007 it was decided to repeal Directive 70/220 / EEC as of January 2013 and the driving cycle, which is also otherwise defined, was recommended for testing.

To determine the consumption of a vehicle, the driving resistances (rolling and air resistance) of the vehicle on the road must first be precisely determined. Then the measured driving resistances are transferred to a roller dynamometer and then a standardized driving cycle is run. Emissions data are also measured in the process. The fuel consumption is then calculated from the exhaust emissions. In the case of electric cars , the energy consumed by the battery is measured instead.

Only certified EC testing laboratories are allowed to carry out legally binding measurements. In Germany, certification is carried out by the Federal Motor Transport Authority .

The standardized driving cycle takes a total of 1180 seconds, i.e. just under 20 minutes. The city cycle (urban conditions) takes two thirds of this time and the overland cycle (extra-urban conditions) one third. The ambient temperature during the measurement is generally 20 ° C to 30 ° C and has been around the parked vehicle for at least 6 hours. Cold start conditions, accelerations and decelerations are recorded and interpolated.

This test procedure should be more realistic than the earlier determination of the energy consumption according to the old DIN standard, because, for example, the cold start phase is taken into account. Because the entire vehicle can be preheated to up to 30 ° C, the cold start corresponds at best to a technical understanding, but not to the general understanding of (driving up consumption) cold or even frost . In addition, there are only a few guidelines that prohibit manufacturers from using non-series fuel-saving options such as special low-viscosity oils or fuel-saving tires. A study by T&E was published in 2013 , which presented the flexibilities of the directive exploited by automobile manufacturers in an easily understandable way. Some examples are:

No recharging of the vehicle battery during the cycle (in other words, the alternator is disconnected during the cycle).
Masking of joints in the outer shell.
Changing the toe and camber settings of the wheels.
Increased air pressure in the car tires .
Use of the minimum vehicle weight.
Deduction of the 4% tolerance on the measured value.
Avoidance of dragging brakes.
Adaptation of the engine control (see also Eco-Tuning )

According to T&E, this leads to a difference of 10–20% in consumption (the report is inconsistent in this regard). While the USA is checking the practical relevance and as a result, for example, Hyundai-Kia was penalized in 2012 for unrealistic driving resistance information (rolling and air resistance), the information is not questioned in the EU.

Consumption data for electric hybrid vehicles

These are determined (as of August 2011) using the ECE standard R 101. The formula for plug-in hybrid cars according to ECE standard R 101 is:

${\ displaystyle C = {\ frac {D_ {e} \ cdot C_ {1} + D_ {av} \ cdot C_ {2}} {D_ {e} + D_ {av}}}}$

${\ displaystyle C =}$ Total consumption in l / 100 km, fuel consumption with a fully charged battery, fuel consumption with an empty battery, = purely electric range, 25 km (assumed average distance between two battery charges).
${\ displaystyle C_ {1} =}$
${\ displaystyle C_ {2} =}$
${\ displaystyle D_ {e}}$
${\ displaystyle D_ {av} =}$

The VCD , Auto Bild and others vehemently criticize this procedure:

“It [this standard] defines a driving cycle of a good eleven kilometers for plug-in hybrid cars: a city trip and an overland trip that the plug-ins drive through twice - with full and empty batteries. So first with the electric motor, then with the combustion engine. Both values are combined using a formula. Problem: Because no fuel is used in electric operation, this value is zero, even though 575 grams of CO ₂ are produced during the production of one kilowatt hour (green electricity: 40 g / kWh) and the driver has to pay for the electricity. […] These values are available, but the EU magic formula disguises them. 'Consumption measurement generally has to be changed', demands Nikolaus Steininger from the responsible EU authority. "

- Auto Bild, issue 32/2011

One problem with this type of calculation is that the plug-in vehicle does not consume fuel when it is in electric mode, but uses electrical energy . An indication of the electrical consumption in kWh per 100 km would therefore also be of interest. This energy requirement is included with zero when determining the emissions of the vehicle. This applies to the direct emissions of the vehicle, but the customer has to pay for the energy in addition and, depending on the selected electricity contract, the degree of expansion of regenerative electricity generation, and also on the network utilization, CO ₂ emissions from the Generation by the energy supplier can be added to customer consumption . However, this has not yet been mapped in the standard and cannot be calculated easily.

The error also lies in the fact that the previously charged electrical energy is not taken into account. This systemic error therefore leads to very low standard consumption values.

An exclusive consideration of the pollutant emissions in the production of electricity (transition from tank-to-wheel to well-to-wheel ) would, however, lead to a distortion in favor of the combustion engines, since the expenses for the production and transport of liquid fuels have not been taken into account either. In addition, this approach would lead to regionally different consumption figures, since the expenditures for electricity and fuel production differ greatly from region to region / in different countries, but cannot be influenced by the vehicle manufacturer. Above all, however, the increasing use of regenerative energies has a quasi “automatic” saving effect in e-vehicles, while a vehicle with a combustion engine will always consume the same amount of fuel per 100 km and emit CO ₂ accordingly , but the cost of fuel production will tend to increase .

A specification in the standard about the energy requirement per 100 km in kWh would be possible. The energy content of petrol and diesel can also be specified in kWh. This would then also show how inefficiently the vehicles with combustion engines deal with the amount of chemically stored energy.

Relation to reality and criticism

The standardized driving cycles represent average profiles in order to be able to compare the vehicles with one another. They often do not match the customer's usage profile, especially when there is a lot of short-haul and city traffic. The consumption and emissions at the maximum speed of 120 km / h are only measured over 10 s of the 20-minute test and are therefore hardly included in the average calculation. Higher speeds are not measured at all. But especially at high speeds, the air resistance increases disproportionately to the speed and thus significantly increases the consumption values. The accelerations carried out in the cycle from 0 to 50 km / h within 26 seconds are not realistic, the cycle suppresses such high consumption and pollutant emissions during strong accelerations. Especially for vehicles with higher vehicle masses, e.g. B. SUV , this results in significantly lower consumption values in the driving cycle than in practice.

Furthermore, a reference to exhaust gas legislation must be established, since the legally prescribed emissions behavior of a vehicle can have a considerable influence on fuel consumption. Therefore, the standardized fuel consumption figures for the same vehicle can be different in different countries.

The calculation of consumption assumes an energy-saving driving style . Drivers who do not master this or do not want to practice it, do not or only with difficulty achieve the measured consumption data in real operation. Additional consumers, in particular heating and air conditioning , should be switched off during the measurement, but the compressor must continue to operate.

In the case of vehicles with a manual gearbox , the exact selection of gears is prescribed in the test cycle because it is assumed that the average driver does not always select the most economical gear, but sometimes drives at a higher speed. In vehicles with a manual gearbox and a gearshift indicator, this is followed by a gearshift, which means that the engine is driven at a significantly lower speed and consumption is lower. In vehicles with automatic transmissions or automated manual transmissions, there are no specifications for the choice of gear, the transmission control can always select the most economical gear. In particular, manually shifted vehicles with large-volume engines and / or with a high overall gear ratio are often tested with unnecessarily / unrealistically high speeds, which contributes to increased measured values compared to practice.

According to a test by the ADAC , the norms are up to 25% too optimistic (= too low). In some models, the additional consumption was over 40%.

WLTP measurement method

The Worldwide Harmonized Light Vehicles Test Cycle (WLTC) is intended to provide the consumer with more realistic information than before. This test cycle is mandatory in the EU from September 1, 2017. Experts expect the average WLTC consumption values to be up to 25 percent higher than the NEDC. In addition to the actual driving cycle (Harmonized Driving Cycle), the standardization also affects the measuring procedure (= Duty Test Procedure = DTP).

Comparison of the measurement methods WLTP (WLTC) and NEDC (NEDC)
Measured value	WLTP (WLTC)	NEDC (NEDC)
Start temperature 25 ° C	Cold start	Cold start (from Euro 3) / cold start after 40 s (up to Euro 2)
Cycle time	30 min	20 min
Service life portion	13%	25%
Cycle length	23,250 m	11,000 m
Speed medium	46.6 km / h	34 km / h
Top speed	131 km / h	120 km / h
Drive power medium ¹⁾	11 kW	7 kW
Drive power maximum ²⁾	42 kW	34 kW
Influence of special equipment and air conditioning	No air conditioning. Special equipment for weight, aerodynamics and electrical system requirements (quiescent current) are taken into account	No consideration

¹⁾Without standstill and braking intervals, vehicle data as in the lower consumption limit table

²⁾Vehicle data as in table Lower consumption limit

Artemis cycle

In order to determine consumption and pollutant emissions more realistically, within the framework of an EU project ARTEMIS (Assessment and Reliability of Transport Emission Models and Inventory Systems), the cycle of the same name (CADC, Common Artemis Driving Cycle), was developed, which includes a city section with realistic accelerations, contains a highway portion and a motorway portion. This is not yet binding.

International driving cycles

International standards are the driving cycles of the USA, Japan and Europe, which stand out due to their synthetic cycle, whereas the other cycles are derived from data surveys in reality.

Type approvals in the USA require several driving cycles that simulate, for example, a sharp drive on the highway and a drive with the air conditioning switched on, including artificial solar radiation. The US city cycle FTP 75 (Federal Test Procedure) from 1975 leads to twice the critical amount of pollutants in the NEDC. Since 2008, the US has had five different driving cycles instead of two, each lasting over 90 minutes and starting at 20 ° F (−7 ° C). These driving cycles are carried out regularly by the vehicle manufacturers and repeated in the laboratory of the United States Environmental Protection Agency for 10–15% to check their information .

Japan gradually replaced its previous 10.15 driving cycle around 2010 with its new JC08 cycle.

Lower consumption limit

A theoretical lower limit of energy consumption can be specified for a specific vehicle for each driving cycle . This lowest possible consumption would be achieved with a loss-free drive and complete braking energy recovery. Rolling and air friction alone then determine consumption ${\ displaystyle E _ {\ text {min}}}$

{\ displaystyle E _ {\ text {min}} = (m \ cdot g \ cdot c_ {R} + {\ frac {1} {2}} \ cdot \ rho \ cdot RCS \ cdot c_ {W} \ cdot A ) s_ {N}}

.

The values tabulated below for some cycles apply to the usual standard distance . ${\ displaystyle E _ {\ text {min}}}$ ${\ displaystyle s_ {N} = 100 \, 000 ~ {\ text {m}}}$

Lower consumption limit of a car for different driving cycles
cycle	NEDC (NEDC)	FTP-75	Japan JC08	WLTP (WLTC)
${\ displaystyle RCS / {\ frac {{\ text {m}} ^ {2}} {{\ text {s}} ^ {2}}}}$	362	255	191	513
${\ displaystyle E _ {\ text {min}} / {\ text {MJ}}}$	35	31	29	41
${\ displaystyle E _ {\ text {min}} / {\ text {kWh}}}$	9.8	8.7	8.0	11.2
${\ displaystyle E / {\ text {kWh}}}$	13.0	13.3	12.5	14.7

The assumed vehicle has a weight of , a coefficient of rolling friction of , a coefficient of air friction and a frontal area of . The acceleration due to gravity and the air density are used with or . The relative cubic speed is a characteristic value of the cycle, which is calculated from its speed-time profile and the resulting route length (values see). The integral extends over the cycle duration . The minimum consumption in the last line of the table applies in the event that - as with combustion engines - no braking energy is stored back. (Invoice not shown). ${\ displaystyle m = 1500 ~ {\ text {kg}}}$ ${\ displaystyle c_ {R} = 0 {,} 015}$ ${\ displaystyle c_ {W} = 0 {,} 25}$ ${\ displaystyle 2 {,} 4 ~ {\ text {m}} ^ {2}}$ ${\ displaystyle g = 9 {,} 81 ~ {\ text {m / s}} ^ {2}}$ ${\ displaystyle \ rho = 1 {,} 2 ~ {\ text {kg / m}} ^ {3}}$ ${\ displaystyle RCS = {\ frac {1} {s_ {Z}}} \ int _ {(T)} v ^ {3} (t) \, {\ text {d}} t}$ ${\ displaystyle v (t)}$ ${\ displaystyle s _ {\ text {Z}}}$ ${\ displaystyle T}$ ${\ displaystyle E}$

The equivalent fuel consumption results from the energy content of 8.9 kWh in 1 liter of gasoline (see Miles per gallon gasoline equivalent ).

literature

Hans-Hermann Braess , Ulrich Seiffert (Hrsg.): Vieweg manual automotive technology . 7th edition. Springer Vieweg Verlag, Wiesbaden 2013, ISBN 978-3-658-01690-6 ( limited preview in the Google book search).

Web links

Individual evidence

↑ United Nations: Addendum 100: Regulation No. 101. (PDF) United Nations, April 12, 2014, accessed November 20, 2017 .

↑ Council Directive 70/220 / EEC of March 20, 1970 on the approximation of the laws of the member states on measures to counter air pollution by exhaust gases from motor vehicle engines with positive ignition , accessed on December 28, 2013

↑ Car advertising and fuel consumption (PDF; 82 kB) In: Self-restrictions of the Austrian advertising industry . Association of Austrian Newspapers . Archived from the original on October 31, 2007. Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved December 28, 2013. @1@ 2

↑ Wolf-Heinrich Hucho (Ed.): Aerodynamics of the automobile . 5th edition. Vieweg + Teubner Verlag , 2005, ISBN 3-528-03959-0 , pp. 138 ( excerpt online from Google [accessed December 28, 2013]).

↑ Directive 91/441 / EEC of the Council of June 26, 1991 amending Directive 70/220 / EEC on the approximation of the laws of the Member States relating to measures against air pollution by emissions from motor vehicles , accessed on December 28, 2013

^ Working groups and committees . European Commission. Archived from the original on January 3, 2014. Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved December 28, 2013. @1@ 2

↑ Directive 93/116 / EEC of the Commission of December 17, 1993 on the adaptation of the Council Directive 80/1268 / EEC on the fuel consumption of motor vehicles to technical progress , accessed on December 28, 2013

↑ Development of the fuel consumption of imported passenger cars since 1990 . In: Fuel consumption and pollutant emissions in imported vehicles continue to fall . Association of International Motor Vehicle Manufacturers. April 27, 2001. Archived from the original on December 30, 2013. Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved December 28, 2013. @1@ 2

^ ^A ^b Karl-Heinz Dietsche, Konrad Reif (Hrsg.): Kraftfahrtechnisches Taschenbuch . 27th edition. Vieweg + Teubner Verlag, 2011, ISBN 978-3-8348-1440-1 , pp. 505 ( excerpt online from Google [accessed on August 3, 2014]).

↑ Regulation (EC) No. 715/2007 of the European Parliament and of the Council of June 20, 2007 on the type approval of motor vehicles with regard to emissions from light passenger cars and commercial vehicles (Euro 5 and Euro 6) and on access to repair and maintenance information for vehicles , accessed December 28, 2013

↑ Handelsblatt, March 15, 2012: Fuel consumption as in paradise , accessed May 21, 2012

↑ ^a ^b T&E, March 13, 2013: Mind the Gap! Why official car fuel economy figures don't match up to reality , accessed April 18, 2013

↑ ^a ^b spiegel.de: embellished consumption figures: BMW has to compensate mini buyers in the USA

↑ Regulation No. 101 of the United Nations Economic Commission for Europe (UN / ECE) , accessed on September 26, 2015

↑ Auto Bild, No. 32/2011 of 12 December 2011, page 88: to green, to be true

↑ Richard van Basshuysen (Ed.): Otto engine with direct injection - process · systems · development · potential . 3. Edition. Springer Vieweg, Wiesbaden, 2013, ISBN 978-3-658-01408-7 , p. 192

↑ see UN Regulation No.101, Annex 6: “ The passenger compartment heating system shall be switched off, as shall any air conditioning system, but such systems compressor shall be functioning normally. ”

↑ Focus November 27, 2007 Fuel consumption Good in the catalog, ugh in practice

↑ Frank-Thomas Wenzel: Economical only in the prospectus In: Frankfurter Rundschau from September 28, 2014

↑ Automobilwoche, May 11, 2013, "EU wants more realistic and globally valid consumption figures from 2017"

^ Homepage of the working group at UNECE

↑ M. André: Real-world driving cycles for measuring cars pollutant emissions . Part A: The ARTEMIS European driving cycles , Report INRETS-LTE 0411, June 2004, inrets.fr ( Memento of the original from January 31, 2012 in the Internet Archive ; PDF) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2
↑ Heinz Steven: Homologation test cycles worldwide. (PDF; 1.24 MB) International Energy Agency , April 30, 2013, accessed on May 17, 2015 .
↑ Gregor Honsel: Good curves, bad curves . In: Technology Review . No. 4/2007 . Heise Zeitschriften Verlag , p. 97–98 ( excerpt online , Spiegel Online ).
↑ Detailed Test Information. United States Department of Energy , United States Environmental Protection Agency, accessed May 17, 2015 .
^ How Vehicles Are Tested. United States Environmental Protection Agency, accessed May 17, 2015 .
↑ Japanese JC08 Cycle (php). Retrieved April 8, 2017.
↑ A reference book of driving cycles for use in the measurement of road vehicle emissions (PDF; 82 kB) Retrieved on March 26, 2017.

[1] United Nations: Addendum 100: Regulation No. 101. (PDF) United Nations, April 12, 2014, accessed November 20, 2017 .

[70/220/EWG-2] Council Directive 70/220 / EEC of March 20, 1970 on the approximation of the laws of the member states on measures to counter air pollution by exhaust gases from motor vehicle engines with positive ignition , accessed on December 28, 2013