New European Driving Cycle
Encyclopedia
The New European Driving Cycle is a driving cycle
consisting of four repeated ECE-15 driving cycles and an Extra-Urban driving cycle (EUDC). The NEDC is supposed to represent the typical usage of a car in Europe
, and is used, among other things, to assess the emission levels of car engines. It is also referred to as MVEG cycle (Motor Vehicle Emissions Group).
, they are generally performed on a roller test bench. This type of bench is equipped with an electrical machine
to emulate resistance due to aerodynamic drag
and vehicle mass
(inertia). For each vehicle configuration, a look-up table is applied: each speed corresponds to a certain value of resistance (reverse torque
applied to the drive wheels). This arrangement enables the use of a single physical vehicle to test all vehicle body styles (Sedan, hatchback, MPV...) by simply changing the look-up table. A fan is coupled to the roller bench to provide the vehicle air intakes with an airflow matching the current speed. Many more tests can be performed during vehicle development with this arrangement than with conventional road tests.
The test is conducted with all ancillary loads turned off (Air conditioning compressor and fan, lights, heated rear window, etc.)
The following parameters are also generally measured to validate the compliance to European emission standards
:
The NEDC was conceived at a time when European vehicles were lighter and less powerful. The transient velocities are much steeper in practice and more dynamic caused by the power surplus of modern engines. Drivers tend to use this excess power failing to achieve the EDC-values in practice. The worst scenario is the absence of regulations above 120 km/h whilst on German motorways velocities above 200km/h are driven.
A new version of the driving cycle should be realistic towards the daily use of ancillary units and gadgets which tend to invade modern vehicles.
For the emission standards to deliver real emission reductions it is crucial to use a test cycle that reflects real-world driving style. It was discovered that engine manufacturers would engage in what was called 'cycle beating' to optimise emission performance to the test cycle, while emissions from typical driving conditions would be much higher than expected, undermining the standards and public health. In one particular instance, research from two German technology institutes found that for diesel cars no 'real' NOx reductions have been achieved after 13 years of stricter standards.
Driving cycle
A driving cycle is a series of data points representing the speed of a vehicle versus time.Driving cycles are produced by different countries and organizations to assess the performance of vehicles in various ways, as for example fuel consumption and polluting emissions.Fuel consumption and...
consisting of four repeated ECE-15 driving cycles and an Extra-Urban driving cycle (EUDC). The NEDC is supposed to represent the typical usage of a car in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, and is used, among other things, to assess the emission levels of car engines. It is also referred to as MVEG cycle (Motor Vehicle Emissions Group).
Plot
Note: The old European driving cycle ECE-15 driving cycle lies between the time period 0s to 800s. For the urban drive cycle the ECE-15 driving cycle is used, and for urban/sub-urban drive cycle the New European Driving Cycle (NEDC) is used to simulate representative driving conditions.Test procedure
The cycle must be performed on a cold vehicle at 20-30°C (typically run at 25°C). The cycles may be performed on a flat road, in the absence of wind. However, to improve repeatabilityRepeatability
Repeatability or test-retest reliability is the variation in measurements if they would have been taken by a single person or instrument on the same item and under the same conditions. A less-than-perfect test-retest reliability causes test-retest variability. Such variability can be caused by, for...
, they are generally performed on a roller test bench. This type of bench is equipped with an electrical machine
Electrical machine
An electrical machine is the generic name for a device that converts mechanical energy to electrical energy, converts electrical energy to mechanical energy, or changes alternating current from one voltage level to a different voltage level....
to emulate resistance due to aerodynamic drag
Drag (physics)
In fluid dynamics, drag refers to forces which act on a solid object in the direction of the relative fluid flow velocity...
and vehicle mass
Mass
Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...
(inertia). For each vehicle configuration, a look-up table is applied: each speed corresponds to a certain value of resistance (reverse torque
Torque
Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....
applied to the drive wheels). This arrangement enables the use of a single physical vehicle to test all vehicle body styles (Sedan, hatchback, MPV...) by simply changing the look-up table. A fan is coupled to the roller bench to provide the vehicle air intakes with an airflow matching the current speed. Many more tests can be performed during vehicle development with this arrangement than with conventional road tests.
The test is conducted with all ancillary loads turned off (Air conditioning compressor and fan, lights, heated rear window, etc.)
Measurements
Several measurements are usually performed along the cycle. The figures made available to the general public are:- Urban fuel economy (first 780 seconds)
- Extra-Urban fuel economy (780 to 1180s)
- Overall fuel economy (complete cycle)
- CO2 emission (complete cycle)
The following parameters are also generally measured to validate the compliance to European emission standards
European emission standards
European emission standards define the acceptable limits for exhaust emissions of new vehicles sold in EU member states. The emission standards are defined in a series of European Union directives staging the progressive introduction of increasingly stringent standards.Currently, emissions of...
:
- Carbon monoxideCarbon monoxideCarbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...
- Unburnt hydrocarbons
- Nitrogen oxides
- Particulate matter
Criticism
- Applicability to current vehicles:
The NEDC was conceived at a time when European vehicles were lighter and less powerful. The transient velocities are much steeper in practice and more dynamic caused by the power surplus of modern engines. Drivers tend to use this excess power failing to achieve the EDC-values in practice. The worst scenario is the absence of regulations above 120 km/h whilst on German motorways velocities above 200km/h are driven.
A new version of the driving cycle should be realistic towards the daily use of ancillary units and gadgets which tend to invade modern vehicles.
- Cycle beating:
For the emission standards to deliver real emission reductions it is crucial to use a test cycle that reflects real-world driving style. It was discovered that engine manufacturers would engage in what was called 'cycle beating' to optimise emission performance to the test cycle, while emissions from typical driving conditions would be much higher than expected, undermining the standards and public health. In one particular instance, research from two German technology institutes found that for diesel cars no 'real' NOx reductions have been achieved after 13 years of stricter standards.
External links
ETC test cycle, ELR test, ESC test more...- http://www.dieselnet.com/standards/cycles/ece_eudc.html