This article needs attention from an expert in Transport. The specific problem is: To distinguish from the fuel economy article. See the talk page for details.(April 2014) |
This article is part of a series on |
Driving cycles |
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Europe |
NEDC: ECE R15 (1970) / EUDC (1990) (UN ECE regulations 83 and 101) |
United States |
EPA Federal Test: FTP 72/75 (1978) / SFTP US06/SC03 (2008) |
Japan |
10 mode (1973) / 10-15 Mode (1991) / JC08 (2008) |
Global Technical Regulations |
WLTP (2015) (Addenda 15) |
The New European Driving Cycle (NEDC) was a driving cycle, last updated in 1997, designed to assess the emission levels of car engines and fuel economy in passenger cars (which excludes light trucks and commercial vehicles). It is also referred to as MVEG cycle (Motor Vehicle Emissions Group).
The NEDC, which is supposed to represent the typical usage of a car in Europe, is repeatedly criticised for delivering economy-figures which are unachievable in reality. It consists of four repeated ECE-15 urban driving cycles (UDC) and one Extra-Urban driving cycle (EUDC). The WLTP test cycle replaced NEDC for vehicles approved for sale in Europe after September 2018, and all published figures for vehicles on sale after January 2019 should use WLTP fuel economy figures [1]
The NEDC test procedure is defined in UNECE R101 [2] for the measurement of CO2 and fuel consumption and/or the measurement of electric energy consumption and electric range in hybrid and fully electric M1 and N1 vehicles, and UNECE R83 [3] for the measurement of emission of pollutants of M, N1 and M2 vehicles. It was maintained by the UNECE World Forum for Harmonization of Vehicle Regulations (WP.29), [4] which also worked on its successor, the Worldwide harmonized Light vehicles Test Procedures (WLTP). [5]
Although originally designed for petrol-based road vehicles, the driving cycle is now also used for diesel vehicles and to estimate the electric power consumption and driving range of hybrid and battery electric vehicles.
UNECE regulation 15 has become obsolete with introduction of UNECE regulation 83 related to "emission of pollutants according to engine fuel requirements".
Several measurements are usually performed along the cycle. The figures made available to the general public are:
The following parameters are also generally measured to validate the compliance to European emission standards:
Some or all of the following parameters are measured depending upon the requirements of the region implementing the test:
The region implementing the test defines limits for each of the pollutants, for instance the Euro level within the EU.
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 repeatability, 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 etc.) 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 Urban Driving Cycle ECE-15 (or just UDC) was introduced first in 1970 as part of ECE vehicle regulations; the recent version is defined by ECE R83, R84 and R101. [2] [3] [6] The cycle has been designed to represent typical driving conditions of busy European cities, and is characterized by low engine load, low exhaust gas temperature, and a maximum speed of 50 km/h. [7]
When the engine starts, the car pauses for 11 s - if equipped with a manual gearbox, 6 s in neutral (with clutch engaged) and 5 s in the 1st gear (with clutch disengaged) - then slowly accelerates to 15 km/h in 4 s, cruises at constant speed for 8 s, brakes to a full stop in 5 s (manual: last 3 s with clutch disengaged), then stops for 21 s (manual: 16 s in neutral, then 5 s in the 1st gear).
At 49 s, the car slowly accelerates to 32 km/h in 12 s (manual: 5 s in 1st gear, 2 s gear change, then 5 s in the 2nd gear), cruises for 24 s, slowly brakes to a full stop in 11 s (manual: last 3 s with clutch disengaged), then pauses for another 21 s (manual: 16 s in neutral, 5 s in the 1st gear).
At 117 s, the car slowly accelerates to 50 km/h in 26 s (manual: 5 s, 9 s and 8 s in the 1st, 2nd and 3rd gears, with additional 2 × 2 s for gear changes), cruises for 12 s, decelerates to 35 km/h in 8 s, cruises for another 13 s, brakes to a full stop in 12 s (manual: 2 s change to the 2nd gear, 7 s in the 2nd gear, last 3 s with clutch disengaged), then pauses for 7 s (manual: in neutral with clutch engaged).
The cycle ends on 195 s after a theoretical distance of 994.03 meters, then it repeats four consecutive times. Total duration is 780 s (13 minutes) over a theoretical distance of 3976.1 meters, with an average speed of 18.35 km/h.
The Extra-Urban Driving Cycle EUDC, introduced by ECE R101 in 1990, [2] has been designed to represent more aggressive, high speed driving modes. The maximum speed of the EUDC cycle is 120 km/h; low-powered vehicles are limited to 90 km/h. [7]
After a 20 s stop - if equipped with manual gearbox, in the 1st gear with clutch disengaged - the car slowly accelerates to 70 km/h in 41 s (manual: 5 s, 9 s, 8 s and 13 s in the 1st, 2nd, 3rd and 4th gears, with additional 3 × 2 s for gear changes), cruises for 50 s (manual: in the 5th gear [sic]), decelerates to 50 km/h in 8 s (manual: 4 s in the 5th and 4 s in the 4th gear [sic]) and cruises for 69 s, then slowly accelerates to 70 km/h in 13 s .
At 201 s, the car cruises at 70 km/h for 50 s (manual: in the 5th gear), then slowly accelerates to 100 km/h in 35 s and cruises for 30 s (manual: in the 5th or 6th gear).
Finally, at 316 s the car slowly accelerates to 120 km/h in 20 s, cruises for 10 s, then slowly brakes to a full stop in 34 s (manual: in the 5th or 6th gear, last 10 s with clutch disengaged), and idles for another 20 s (manual: in neutral).
Total duration is 400 s (6 minutes 40 s seconds) and theoretical distance is 6956 meters, with an average speed of 62.6 km/h.
The combined fuel economy is calculated by a total consumption of urban and extra-urban cycles over the total distance (theoretical 10932 meters). The total test time amounts to 1180 s with an average speed of 33.35 km/h. Sometimes the NEDC is also quoted at 1220 s, which includes the initial 40 s with the vehicle at standstill and combustion engine off.
The NEDC was conceived when European vehicles were lighter and less powerful. The test offers a stylized driving speed pattern with low accelerations, constant speed cruises, and many idling events. However, accelerations are much steeper and variable in practice, [8] which is in part caused by the power surplus of modern engines as the 0–100 km/h (0–62 mph) average-time decreased from 14 seconds in 1981 to 9 seconds in 2007. [9] In 1998, a Swedish researcher criticized the NEDC standard for allowing large emission differences between test and reality. [10]
The UK consumer group Which?, criticized the NEDC test procedure as being out-of-date as its most recent update was made in 1997; [11] before hybrid cars and stop-start technology was generally available. The group claimed the test did not replicate real-world driving conditions and had numerous loopholes which cause the results to be unachievable in practice. It was also claimed that no official body polices the tests and the vehicle manufacturers can arbitrarily reduce their results by 4% at the end of the cycle. Weaknesses noted are: (i) that tests are not necessarily repeatable and comparable; (ii) the test-cycle does not include sustained motorway driving; (iii) test-cycles can be performed using optional economy settings which will not typically be selected by drivers; (iv) the test-cycle is performed with ancillary equipment such an air-conditioning and heated windows switched off; (v) the tests can be conducted at 2 km/h (1.2 mph) below the required speed thus using less fuel; (vi) roof-rails and passenger door-mirror can be removed for the test, to reduce drag; (vii) tyre inflation for the test can be set above the recommended pressure values to artificially reduce rolling resistance.
For the emission standards to deliver real emission reductions it is crucial to use a test cycle that reflects real-world driving style. However, the fixed speeds, gear shift points and accelerations of the NEDC offer possibilities for manufacturers to engage in what is called 'cycle beating' to optimise engine emission performance to the corresponding operating points of the test cycle, while emissions from typical driving conditions would be much higher than expected, undermining the standards and public health. [8] 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. [12]
It is alleged that, under NEDC, some automakers overinflate tires, adjusting or disconnecting brakes to reduce friction, and taping cracks between body panels and windows to reduce air resistance, some go as far as removing wing mirrors, to inflate measured fuel economy and lower measured carbon emission. [13]
In addition, the height of the simulated wind fan could alter the performance of after-treatment systems due to changes in temperature and, consequently, modify the pollutant emissions values. [14]
UNECE WP29 is currently developing a new global harmonized driving cycle, the World Light Test Procedure (WLTP) with participation of experts from the European Union, India, and Japan; it will apply to light duty vehicles (i.e. passenger cars and light commercial vans). [15]
The European Commission intends to introduce a type approval procedure to measure the energy efficiency of mobile air conditioning systems in vehicles, as well as its effect on fuel consumption and emissions, and display an efficiency label on the vehicle; the work is being performed by TU Graz (Institute for Internal combustion engines and Thermodynamics), Aristotle University of Thessaloniki (Laboratory of Applied Thermodynamics), TNO and ACEA. [16]
A clutch is a mechanical device that allows the output shaft to be disconnected from the rotating input shaft. The clutch's input shaft is typically attached to a motor, while the clutch's output shaft is connected to the mechanism that does the work.
A hybrid vehicle is one that uses two or more distinct types of power, such as submarines that use diesel when surfaced and batteries when submerged. Other means to store energy include pressurized fluid in hydraulic hybrids.
A vehicle start-stop system or stop-start system automatically shuts down and restarts the internal combustion engine to reduce the amount of time the engine spends idling, thereby reducing fuel consumption and emissions. This is most advantageous for vehicles which spend significant amounts of time waiting at traffic lights or frequently come to a stop in traffic jams. Start-stop technology may become more common with more stringent government fuel economy and emissions regulations. This feature is present in hybrid electric vehicles, but has also appeared in vehicles which lack a hybrid electric powertrain. For non-electric vehicles fuel economy gains from this technology are typically in the range of 3–10%, potentially as high as 12%. In the United States, idling wastes approximately 14.8 billion liters of gasoline per year.
Overdrive is the operation of an automobile cruising at sustained speed with reduced engine revolutions per minute (RPM), leading to better fuel consumption, lower noise, and lower wear. The term is ambiguous. The most fundamental meaning is that of an overall gear ratio between engine and wheels, such that the car is over-geared, and cannot reach its potential top speed, i.e. the car could travel faster if it were in a lower gear, with the engine turning at higher RPM.
The Mercedes-Benz B-Class is a subcompact executive car manufactured and marketed by Mercedes-Benz since 2005. Based on the A-Class with larger dimensions, the European New Car Assessment Programme classifies it as a small MPV.
A direct-shift gearbox is an electronically-controlled, dual-clutch, multiple-shaft, automatic gearbox, in either a transaxle or traditional transmission layout, with automated clutch operation, and with fully-automatic or semi-manual gear selection. The first dual-clutch transmissions were derived from Porsche in-house development for the Porsche 962 in the 1980s.
A driving cycle is a series of data points representing the speed of a vehicle versus time.
The European emission standards are vehicle emission standards for pollution from the use of new land surface vehicles sold in the European Union and European Economic Area member states and the United Kingdom, and ships in EU waters. The standards are defined in a series of European Union directives staging the progressive introduction of increasingly stringent standards.
The World Forum for Harmonization of Vehicle Regulations is a working party (WP.29) of the Inland Transport Committee (ITC) of the United Nations Economic Commission for Europe (UNECE). Its responsibility is to manage the multilateral Agreements signed in 1958, 1997 and 1998 concerning the technical prescriptions for the construction, approval of wheeled vehicles as well as their Periodic Technical Inspection and, to operate within the framework of these three Agreements to develop and amend UN Regulations, UN Global Technical Regulations and UN Rules, kind of vehicle regulation.
A transmission control unit (TCU), also known as a transmission control module (TCM), or a gearbox control unit (GCU), is a type of automotive ECU that is used to control electronic automatic transmissions. Similar systems are used in conjunction with various semi-automatic transmissions, purely for clutch automation and actuation. A TCU in a modern automatic transmission generally uses sensors from the vehicle, as well as data provided by the engine control unit (ECU), to calculate how and when to change gears in the vehicle for optimum performance, fuel economy and shift quality.
The fuel economy of an automobile relates to the distance traveled by a vehicle and the amount of fuel consumed. Consumption can be expressed in terms of the volume of fuel to travel a distance, or the distance traveled per unit volume of fuel consumed. Since fuel consumption of vehicles is a significant factor in air pollution, and since the importation of motor fuel can be a large part of a nation's foreign trade, many countries impose requirements for fuel economy. Different methods are used to approximate the actual performance of the vehicle. The energy in fuel is required to overcome various losses encountered while propelling the vehicle, and in providing power to vehicle systems such as ignition or air conditioning. Various strategies can be employed to reduce losses at each of the conversions between the chemical energy in the fuel and the kinetic energy of the vehicle. Driver behavior can affect fuel economy; maneuvers such as sudden acceleration and heavy braking waste energy.
The Smart Forfour is a city car (A-segment) marketed by Smart over two generations. The first generation was marketed in Europe from 2004 to 2006 with a front-engine configuration, sharing its platform with the Mitsubishi Colt. The second generation was marketed in Europe from 2014 after an eight-year hiatus, using rear-engine or rear electric motor configurations. It is based on the third-generation Renault Twingo, which also forms a basis for the third-generation Smart Fortwo. A battery electric version was marketed as the EQ Forfour beginning in 2018.
Energy-efficient driving techniques are used by drivers who wish to reduce their fuel consumption, and thus maximize fuel efficiency. The use of these techniques is called "hypermiling".
The BMW i8 is a plug-in hybrid sports car developed by BMW. The i8 was part of BMW's electrified fleet and was marketed under the BMW i sub-brand. The production version of the BMW i8 was unveiled at the 2013 Frankfurt Motor Show and was released in Germany in June 2014. Deliveries to retail customers in the U.S. began in August 2014. A roadster variant was launched in May 2018. Production ended in June 2020.
The EPA Federal Test Procedure, commonly known as FTP-75 for the city driving cycle, are a series of tests defined by the US Environmental Protection Agency (EPA) to measure tailpipe emissions and fuel economy of passenger cars.
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