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Enhanced Road Load Determination Procedure for Accurate Fuel Consumption Figures

This paper presents a new road load test procedure for production vehicles to ensure realistic fuel consumption figures. It addresses the shortcomings of the current ISO 10521 procedure, showcasing the impact of road load on CO2 emissions and the need for improvements. Recommendations include a feed-back approach, updating legislation, and forming a task force for further discussions and proposals.

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Enhanced Road Load Determination Procedure for Accurate Fuel Consumption Figures

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  1. WLTP-DTP-LabProcICE-040a Roadloaddetermination Representative road load test procedure Peter Smeds – Swedish Transport AdministrationIddo Riemersma – Transport & Environment

  2. Problemdescription • Customer expectation: Realistic fuel consumption figures • Required: Test procedure aiming at representative conditions for production vehicles (cycle, road load, temperature etc.) • Road load not tested on production vehicle, but on a pre-production vehicle • ‘Flexibilities’ in current ISO 10521 road load test procedure: this offsets the homologation test results • Improving RLD procedure creates a level playing field

  3. Justification data • TŰV Nord showed reductions of CO2emissions of 2 to 10% on NEDC test cycle for reduced road load(-20% at 20 km/h, -10% at 40 – 120 km/h) • TU Graz measured 9 to 24% higher CO2emissions compared to TA value on 6 production vehicles by applying actual measured road load. • EPA road load verification programme on 24 vehicles resulted in 7% higher road load on average.

  4. Examples of issues of current ISO 10521 • Wheel alignment • Brake preparation • Test tracks (climate, road surface, inclination) • Tires (wear, pressure, choice of type) • Vehicle characteristics (body, accessories, weight) • Other issues  Straightforward approach: add requirements to the GTR

  5. Alternative approach Feed forward approach Feed back approach  Feed back loop via CoP or in-use conformity Requirements Requirements Coast down test vehicle Road load data Production vehicle Requirements Requirements Requirements Requirements Coast down test vehicle Road load data Production vehicle Road load data

  6. Conclusions & recommendations • Clear indications for an offset in CO2 due to unrealistic road load • Identified flexibilities in ISO 10521 can be solved to some extent • Some gaps will remain and tolerances have to be allowed • Best guarantee for a representative road load is the feed back approach • Existing legislation and targets for CO2 need to be reviewed if RLD procedure is changed

  7. Next steps • Starting a small taskforce group to discuss the issues identified in the paper • Preparing a proposal for an improved RLD procedure in the draft GTR. • Starting a measurement program to determine the offset in CO2

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