Browse Publications Technical Papers 2019-26-0357
2019-01-19

Real-World Fuel Consumption Measurement as the Base for the Compliance to Future CO2 Regulations 2019-26-0357

The gap between the officially reported CO2 values and the actual performance of the vehicle on the road is continuously increasing. Numerous studies are showing differences between the official values and the real-world measurements of more than 40% in average, with further increases year by year. The fuel consumption of passenger cars are determined as part of the vehicle certification according to Euro 6 via carbon mass balance using exhaust gas measurement. By introducing the new world harmonized driving cycle (WLTC) in September 2017, which is addressing a more realistic speed profile or traffic conditions, the gap between the certification and road test is expected to be reduced in half. Additionally the EU Commission plans to monitor vehicles more closely. From 2020, devices for recording fuel and energy consumption will become mandatory in all passenger cars and light commercial vehicles, reflecting the average real world CO2 emissions. During the type approval the OEMs have to prove that these so called 'On-board Fuel and/or Energy Consumption Monitoring Device' ('OBFCM device') is not deviating more than +/- 5% compared to the fuel consumption value calculated from the carbon mass balance. OBFCM means that by using already existing devices in the vehicle, like the ECU, the quantity of fuel and/or electric energy used is being determined and stored. This is obviously a challenging target considering a typically uncertainty of the carbon mass balance determination of +/- 3% with reference to precise direct fuel flow measurement. The most important task will be to achieve an accurate reference value for the ECU calibration via direct fuel flow measurement. The target of the paper is a comparison of the indirect methods of carbon mass balance as well as ECU fuel consumption determination and the direct fuel flow measurement by means of measurement uncertainty considerations and actual measurements.

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