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WHAT IS WLTP? AND HOW DOES IT WORK?

WHAT IS WLPT ? (Worldwide Harmonised Light Vehicle Test Procedure)  AND HOW DOES IT WORK?

Under conditions defined by EU law, the Worldwide Harmonised Light Vehicle Test Procedure (WLTP) laboratory test is used to measure fuel consumption and CO2 emissions from passenger cars, as well as their pollutant emissions.

The old lab test – called the New European Driving Cycle (NEDC) – was designed in the 1980s. Due to evolutions in technology and driving conditions, it became outdated. The European Union has therefore developed a new test, called the Worldwide Harmonised Light Vehicle Test Procedure (WLTP). The EU automobile industry welcomes the shift to WLTP and has actively contributed to the development of this new test cycle.

While the old NEDC test determined test values based on a theoretical driving profile, the WLTP cycle was developed using real-driving data, gathered from around the world. WLTP therefore better represents everyday driving profiles.

The WLTP driving cycle is divided into four parts with different average speeds: low, medium, high and extra high. Each part contains a variety of driving phases, stops, acceleration and braking phases. For a certain car type, each powertrain configuration is tested with WLTP for the car’s lightest (most economical) and heaviest (least economical) version.

WLTP was developed with the aim of being used as a global test cycle across different world regions, so pollutant and CO2 emissions as well as fuel consumption values would be comparable worldwide. However, while the WLTP has a common global ‘core’, the European Union and other regions will apply the test in different ways depending on their road traffic laws and needs.

WHAT IS THE LINK BETWEEN THE CO2 EMISSIONS AND FUEL CONSUMPTION OF MY CAR?

The amount of CO2 a car emits is directly related to the amount of fuel it consumes. For instance, a diesel car emitting 95g CO2 per kilometre consumes around 3.7 litres of fuel per 100km, while a petrol car consumes around 4 litres/100km for the same CO2 emissions.

Fuel efficiency, sometimes referred to as fuel economy, is the relationship between the distance travelled and the fuel consumed.

WILL WLTP END THE DISCREPANCY BETWEEN THE LABORATORY AND ON-ROAD PERFORMANCE OF CARS?

Even though the Worldwide Harmonised Light Vehicle Test Procedure (WLTP) will provide a far more realistic representation of conditions encountered on the road than the old NEDC lab test (New European Driving Cycle), it will not cover all possible variations. Moreover, each individual driver will continue to have a different driving style: one driver might accelerate faster, take corners faster or brake more suddenly than another who might drive more conservatively.

Given that driving behaviour, traffic and weather conditions will continue to differ from one country to another, there will still be a difference between emissions measured in lab conditions and the real world. However, as there is no single real-world emission value, only values obtained by standardised laboratory tests allow us to directly compare the emissions and fuel consumption of different car models from different car manufacturers

WLTP will introduce much more realistic testing conditions. These include:

  • More realistic driving behaviour
  • A greater range of driving situations (urban, suburban, main road, motorway);
  • Longer test distances;
  • More realistic ambient temperatures, closer to the European average;
  • Higher average and maximum speeds;
  • Higher average and maximum drive power;
  • More dynamic and representative accelerations and decelerations;
  • Shorter stops;
  • Optional equipment: CO2 values and fuel consumption are provided for individual vehicles as built;
  • Stricter car set-up and measurement conditions;
  • Enables best and worst-case values on consumer information, reflecting the options available for similar car models

Because of all these improvements, WLTP will provide a much more accurate basis for calculating a car’s fuel consumption and emissions. This will ensure that lab measurements better reflect the on-road performance of a car.

WILL MY FUEL CONSUMPTION INCREASE UNDER WLTP?

Practically, your car’s fuel consumption performance will not change with these new WLTP values. The Worldwide Harmonised Light Vehicle Test Procedure will result in a higher g/km CO2 value for the one and same vehicle compared to NEDC, simply because it is a more rigorous and longer test – meaning the WLTP will provide a better reflection of today’s situation than the NEDC. In other words, the higher CO2 value does not mean increased fuel consumption, but rather a more realistic CO2 value due to the change in how the vehicles are tested

The old lab test – called the New European Driving Cycle (NEDC) – was designed in the 1980s and became outdated today due to several evolutions in technology and driving conditions.

The European Union has therefore prepared a new test, called the Worldwide Harmonised Light Vehicle Test Procedure (WLTP) that applies from September 2017.

The transition to WLTP will happen in phases:

  • WLTP will officially apply to new types of cars from September 2017. New types of cars are vehicle models that are introduced on the market for the first time.
  • Manufacturers may already start requesting WLTP approvals for new car types when the legislation comes into force in the European Union (no sooner than end July 2017).
  • WLTP will apply to all new car registrations from September 2018.
  • EU measures for end-of-series cars should allow for a limited number of unsold vehicles in stock that were approved under the old test (NEDC) to be sold the following year, that is until September 2019.

The above are extracts that have been taken from WLTP FACTS .EU as a guide on WLTP (Worldwide Harmonised Light Vehicle Test Procedure) full in-depth details can be found on their website www.wltpfacts.eu

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Posted on 30th August 2018 at 10:44 AM

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