Worldwide Harmonised Light Vehicles Test Procedure (WHLVTP)

Foundations and Regulatory Context of WLTP

Objectives and Global Harmonization

• Understanding the transition from the New European Driving Cycle (NEDC) to the Worldwide Harmonised Light Vehicles Test Procedure (WLTP) to provide more realistic emission and fuel consumption data.
• Analysis of the UN Global Technical Regulation (GTR) No. 15, which serves as the technical basis for the WLTP, ensuring consistency across different global markets.
• The role of the WLTP in bridging the gap between laboratory test results and actual on-road vehicle performance by incorporating more dynamic driving phases.

Vehicle Classification and Requirements

• Determining vehicle categories based on the Power-to-Mass (PMR) ratio and maximum speed, which dictates the specific test cycle segments a vehicle must undergo.
• Defining the Road Load parameters, including the influence of vehicle mass, aerodynamic drag, and rolling resistance on laboratory test settings.
• Techniques for determining vehicle inertia and the use of the Coastdown method to calibrate chassis dynamometers to replicate real-world road resistance accurately.

The WLTP Test Cycle and Execution

Dynamic Driving Cycles (WLTC)

• Mastery of the World Harmonised Light Vehicles Test Cycles (WLTC), which are split into four speed-based phases: Low, Medium, High, and Extra-High.
• Understanding the specific gear-shifting procedures required for manual transmissions, which are calculated based on engine speed and power availability rather than fixed speed points.
• Management of vehicle state-of-charge for electrified vehicles, including plug-in hybrids (PHEVs) and battery electric vehicles (BEVs), during the test cycles.

Laboratory Test Conditions

• Standardization of ambient temperature requirements, specifically the 23°C test cell condition, and the impact of temperature deviations on emission outcomes.
• Procedures for pre-conditioning vehicles, including soaking periods and thermal stabilization, to ensure test repeatability and comparability.
• Measurement of tailpipe emissions, including CO2, NOx, particulate matter, and total hydrocarbons, using Constant Volume Sampling (CVS) systems.

Advanced Data Analysis and Compliance

Interpolation and Individual Vehicle Configurations

• The use of the Interpolation Family concept to calculate fuel consumption and CO2 emissions for individual vehicle specifications without testing every single configuration.
• Applying the Correction Factors for aerodynamic drag and mass variances between the 'lowest' and 'highest' energy-consuming vehicles within a family.
• Technical requirements for determining the 'Road Load Matrix Family' for multi-stage vehicle manufacturing and heavy-duty adaptations.

Real Driving Emissions (RDE) Integration

• Understanding how WLTP laboratory results are supplemented by Real Driving Emissions (RDE) testing using Portable Emission Measurement Systems (PEMS).
• Analyzing boundary conditions for RDE, including trip composition (urban, rural, motorway), ambient temperature, altitude, and vehicle payload requirements.
• Applying Conformity Factors to evaluate the difference between laboratory-measured emissions and those recorded during actual road operation to ensure regulatory compliance.

Electrification and Future-Proofing

Testing Electrified Powertrains

• Calculation of Electric Range (ER) and Equivalent All-Electric Range (EAER) for different battery capacities and charging profiles.
• Applying the Utility Factor (UF) to determine the weighted average emissions for plug-in hybrids based on the probability of driving in electric-only mode versus internal combustion mode.
• Managing multi-stage testing for fuel cell vehicles, including the specific measurement of hydrogen consumption and the integration of auxiliary power demands into the total efficiency calculation.