What is WLTP and how does it work

source - wltpfacts.eu

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, By 2020, the WLTP ratings will take full effect

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 Due to evolutions in technology and driving conditions, it became outdated.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 test procedure and has actively contributed to the development of this new test cycle. the WLTP aims to make European fuel economy labels more realistic. They are also expected to result in shorter range estimates for electric cars than the old tests.

While the old NEDC test determined test values based on a theoretical driving profile, the test procedure cycle was developed using real-driving data, gathered from around the world. Under the WLTP tests, it is expected to be rated at 167.7 miles

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 for the car’s lightest (most economical) and heaviest (least economical) version. the new WLTP test protocols in Europe will include testing in real-world on-road driving with mobile test equipment, fallout from the cheating scandal that cost Volkswagen billions.

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.

                                                                      source - BMW

World-Harmonized Light-Duty Vehicles Test Procedure

Regulations governing light-duty vehicle emissions and fuel consumption vary significantly across countries and markets. Manufacturers face additional costs to certify their vehicles under several procedures and standards, even though the fundamental purpose of all regulations is essentially the same: to reduce pollutant emissions and improve fuel efficiency.

 Harmonizing the test methodology and the test cycle will reduce these costs to the benefit of both manufacturers and consumers. 

A harmonized approach will also make it easier to compare fuel efficiency and emission standards across regions and countries. Over time, this will improve the effectiveness of air quality targets and CO₂ reduction policies.

The development of the WLTP comprised two main elements:

• Development of a harmonized driving cycle representative of world average driving conditions (internally referred to as the DHC)
• Development of a harmonized test procedure that sets the conditions, requirements, tolerances, etc. for the emissions test (internally referred to as the DTP)

Since the beginning of the WLTP process, the European Union has had a strong political objective, set by its own legislation (Regulations (EC) 443/2009 and 510/2011), to develop and adopt a more realistic test procedure by 2014. 

This was a major driving factor for setting the time frame of phase 1 of the WLTP. Similarly, Japan has also agreed to adopt the WLTP for its fuel efficiency standards, and the existing Japanese 2020 efficiency target for new vehicles will likely be adjusted for the WLTP.

What is different in the wltp test cycle procedure?

The new WLTP measurement process is clearly much more realistic. Test length, test distance and stationary time are measured much more precisely. 

Also new: electric and hybrid vehicles received a special test called the “city phase”. Additional changes are significant: Individual vehicle configurations are considered – for example tyres or even sports seats.

The NEDC test phases (in city, out of city, combined) will be replaced by the phases of WLTP. The new WLTP test procedure for measuring fuel consumption and CO2 values is now much more dynamic. 

The existing NEDC procedure, developed in the 1990s, is totally outdated.  The responsible UN committee therefore decided to create a new testing procedure. The development process required the analysis of over 750,000 driven kilometres covering three continents (Asia, Europe, USA).

After evaluating the data, a test procedure was developed that is valid as of 1 September 2018, for new produced vehicles. The new test should help deliver more precise and reality-based user data. Hybrid and electric cars are also included. 

Source - BMW