Glossary: Key technical terms

ATCT test ( Ambient Temperature Correction Test): Reference test for standardisation of the CO2 measurements in line with the average European temperature of 14 °C using a "family correction factor" (►FCF).

CO2: Carbon dioxide is a chemical compound of carbon and oxygen with the molecular formula CO2. Given a sufficient supply of oxygen, CO2 is produced, for example, when carbon-containing substances are burned. The CO2 emissions of combustion engines are proportional to their fuel consumption.

CO2MPAS tool: Developed and made available by the EU Joint Research Centre (JRC), this open-source software makes it possible to convert WLTP values to NEDC values: https://co2mpas.io/ Since the NEDC values still have to be determined up until the end of 2020 to check the progress of the fleet target achievement and will also still be used for calculating vehicle tax in the near future, Mercedes-Benz uses the CO2MPAS tool as stipulated by the correlation regulation for vehicles certified according to the Euro 6d TEMP/Euro 6d standards. This is used to determine the NEDC values and/or in accordance with the EU regulation to conduct additional test in line with the NEDC.

Conformity of production: A random sample at the end of the production line checks whether the WLTP provisions are being fulfilled.

Euro 6d-TEMP: The European Union sets the emissions limits for motor vehicles in regulations. In the Euro 6d-TEMP emissions phase, an RDE test must confirm both the Euro 6 nitrogen oxide limits and the Euro 6 limits for the particle number taking into consideration legally defined ►conformity factors. In addition, as in the Euro 6c emissions phase, the Euro 6 limits, also measured in the lab, must be confirmed according to WLTP. Euro 6d-TEMP applies to new emission types since 1.9.2017 and to all newly approved vehicles from 1.9.2019. From 2020, emissions must be determined according to the Euro 6d follow-up standard.

Since September 2017, Mercedes-Benz has tested all new emission types according to Euro 6d TEMP or Euro 6d. ►WLTP and ►RDE are part of the new standard. At the same time, ►NEDC consumption and CO2 value will continue to be determined and disclosed in press and advertising material. The ►WLTP test results are converted to NEDC values using the ►CO2MPAS tool required and made available by the authorities. With certain restrictions, NEDC tests are conducted alternatively or in addition in accordance with the EU regulation.

Euro 6d: Emission standard that will be obligatory from 1.1.2020 (for new models) and from 1.1.2021 (for all new vehicles). In contrast to the Euro 6d-Temp, the RDE► conformity factor will be reduced from 2.1 to 1.0 + 0.43.

EVAP (Evaporative Emissions): These evaporative emissions from the fuel system are hydrocarbons. Modern cars have an appropriate capturing system, a so-called activated charcoal reservoir, so that the fuel vapour does not escape into the surrounding air. The filter filled with charcoal absorbs and saves the fuel vapours until they can be burned in the petrol engine. Since the combustion engine in vehicles with plug-in hybrid drives is often not started for long periods of time, and the activated charcoal filters are therefore also not rinsed, they have a pressure tank to safely keep the emissions back.

Drive Trace Indices: Using these indices, in addition to the previous tolerances to deviations (speed of +/- 2 km/h, time +/- 1 s), it is checked whether the driver is following the driving cycle as precisely as possible on the dynamometer and what his driving style is.

In-Service Conformity: Field tests check whether "young" customer vehicles comply with the WLTP provisions. Cars between six months and five years of age and with a mileage of between 15,000 to 100,000 km are selected.

FCF ( Family Correction Factor): Has to be taken into consideration with the ►ATCT test. It serves to correct temperature conditions that are representative for the region and is applied to a vehicle/interpolation family.

Conformity factor: To make allowance for the measuring tolerances of portable emissions measurement systems (►PEMS) and the more stringent requirements of the ►RDE test owing to the increased breadth of ambient conditions, especially in the extended range, evaluation of the RDE results is subject to so-called conformity factors. The Euro 6 limits, when converted with the conformity factors, must not be exceeded in the evaluation. In RDE Phase 1 (Euro 6d-TEMP), this conformity factor is 2.1, RDE Phase 2 it is 1.0 + 0.43 for NOx. The tolerance of 0.5 covers variations in the PEMS measuring equipment. The conformity factor for the particle number is 1.0 + 0.5 (measuring tolerance) for all newly approved vehicles since 1 September 2018.

NEDC: Up until 2018 emission and consumption values in Europe have been determined according to the NEDC (New European Driving Cycle). The first European driving cycle was introduced in 1970 with the aim of providing customers with comparable and reproducible values across all manufacturers. In 1992, it was extended beyond urban driving. Since the inclusion of cold starting in 2000, the NEDC has not undergone any further fundamental change. Up until the end of 2020, NEDC values will continue to be determined in addition to the WLTP values to allow verification of compliance with fleet targets.

New emission type: If, for example, a new engine is installed in a vehicle or an engine is modified so that its emissions behaviour changes or a new or modified transmission is installed or another part of the powertrain is modified or changes are made to the exhaust system, this results in a new emission type according to WLTP.

NOx: Is the collective term for compounds of nitrogen and oxygen. Nitric oxide (NO), nitrogen dioxide (NO2) and nitrous gases are among the nitrogen oxides. They are abbreviated to NOx, as there are several nitrogen/oxygen compounds on account of the many oxidation states of nitrogen. Sometimes, the abbreviation NOx is used synonymously for the nitrous gases produced during the combustion of fossil fuels.

PEMS: The abbreviation stands for Portable Emissions Measurement System. This system can record the exhaust emissions of motor vehicles during real on-road driving. In the European Union, PEMS are used to conduct the RDE procedure as part of type approval.

Phase-in: CO2 discount in the first year (2020) the new measuring procedure is introduced. In this phase-in period, 95% of the vehicles of a vehicle manufacturer have to meet the limits.

PM (Particulate Matter): All matter distributed in the air and perceptible on filters is termed particulate. The particulate is classified according to its aerodynamically effective diameter. Particulate matter (PM10) consists of particulates with an aerodynamic diameter of less than 10 micrometers (µm). Of these particles, some have an aerodynamic diameter of less than 2.5 µm (PM2.5). The fraction of ultra-fine particulates (< 0.1µm) belongs to these. The majority of anthropogenic particulate emissions stem from combustion and production processes. Particulate matter is not only directly emitted (primary particulates), but also forms from precursors (including sulphur dioxide, nitrogen oxide and ammonia) in the atmosphere (2ndary particulate).

PN (Particle Number): Apart from particulate mass, the Euro 6 legislation also sets limits for the number of particles. PEMS measurements means that the particle number can be determined with a number of measuring principles (electric and optical).

RDE (Real Driving Emissions): In connection with compliance with emissions limits with the application of conformity factors, it must be verified – for particulates from emissions phase Euro 6c according to WLTP or additionally for NOx from emissions phase Euro 6d-TEMP – that the Euro 6 limits are not exceeded in road tests within the legally valid parameters. In the past, emissions measurements for type approval were carried out exclusively on a dynamometer. With effect from March 2016, emissions must increasingly also be certified under real driving conditions within defined parameters. Since September 2017, for new emission types the Euro 6 limits for both nitrogen oxides NOx and particulate number PN must be met in RDE road tests subject to the application of conformity factors. From 1 September 2019, this will apply to all newly approved vehicles.

SHED (Sealed Housing for Evaporative Determination/Special test chamber for measuring evaporative emissions of hydrocarbons): The vehicle is brought into a SHED chamber for measurement (hot soak test) less than five minutes after the engine has been switched off following the test on the roller dynamometer. The diurnal soak takes place following the required cooling time outside of the SHED chamber. The SHED chambers allow the usual temperature profiles as required by the CARB, EPA or EU. The ►EVAP provision is new in this context.

Soak: For a number of tests, the vehicles including all operating materials must be at a precisely defined temperature: They are placed on special parking surfaces, or so-called soak surfaces, for this purpose. The laboratory at the Stuttgart location has a large car park for more than 100 vehicles across several storeys with an automated storage system in which the vehicles are preconditioned at a legally defined and stipulated test temperature until they are tested.

Supercredits: Bonus points when calculating fleet consumption. This regulation is meant to support especially efficient vehicles in that they repeatedly feed into a manufacturer's CO2 balance. For example, vehicles that emit less than 50 g of CO2 per kilometre (this corresponds to consumption of approx. 2.15 litres of petrol or 1.9 litres of diesel per 100 kilometres), will be counted twice in the 2020 fleet consumption.

WLTC: The driving cycle of the WLTP is called WLTC – Worldwide Harmonized Light Vehicle Test Cycle. For different vehicle models, the WLTP has three different driving cycles, which take account of the respective power-to-weight ratio. Most cars registered in the EU, which have a power-to-weight ratio of more than 34 kW/t (46 hp/t), are assigned to WLTC Class 3. The test cycle for Class 3 vehicles is made up of four parts – low, medium, high, extra-high. These simulate urban, extra-urban and motorway driving.

WLTP (Worldwide Harmonized Light Vehicle Test Procedure): This test procedure determines a vehicle's consumption and emission values on a roller dynamometer. Since 1 September 2017, the WLTP has been rolled out gradually and replaced the previous NEDC test procedure. Thanks to its dynamic focus, the WLTP is significantly more realistic than the previous procedure. At the same time, many requirements, e.g. in relation to the determination of driving resistances or conducting dynamometer tests, have been made significantly stricter compared with the NEDC. Especially these modified parameters lead to a numerical increase of the CO2 values, although the efficiency of the vehicles is not changed by the new measurement procedure.

WLTP 2nd Act : Latest EU regulation on the WLTP with extensive changes. Regulation 2018/1832 was published in the EU Gazette on 27 November 2018, and it has been in use since 17 December 2018. And since 1 January 2019, the "2nd Act" is obligatory for all new models to be certified.

Type 1 certification test: Test procedure to determine the consumption and/or the CO2 emissions. Other tests include Type 2 (CO emissions in idle), Type 3 (emissions from the crankcase) and Type 4 (checking fuel evaporation in vehicles with a petrol engine).

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