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Specific test systems are essential for the development and optimization of powertrains for two-wheeler applications. The World Motorcycle Test Cycle (WMTC) is prevalently used for type approval certification in terms of emissions and fuel consumption. In this respect, decreasing fuel consumption and increasing efficiency within the WMTC is an important development goal. The aim of the development project presented in this paper was to investigate how the robustness and repeatability of the measurement data can be increased by using a specific measurement procedure and test setup. As fuel consumption and emission levels reach ever lower levels, any influencing factors related to performance and emissions are of particular interest within the powertrain development phase. When it comes to the differentiation of specific influencing factors such as lube oil behavior and its contribution to fuel consumption, very high measurement-repeatability and accuracy must be maintained.

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.

The development process of a combustion engine is now a days strongly influenced by future emission regulations which require further reduction in fuel consumption and precise control of combustion process based on Intake air measurement, during engine development. Intake air flow meters clearly differentiate themselves from typical industrial gas flow meters because of their ability to measure extremely dynamic phenomenon of combustion engine. Thus, high internal data acquisition rate, short response time, ability to measure pulsating and reverse flows with lower measurement uncertainty are the factors that ensures the reliability of the results without being affected by ambient influences, sensor contamination or sensor aging. The AVL developed FLOWSONIX™ is based on ultrasonic transit time measuring principle with broad-band Capacitive Ultrasonic Transducer (CUT) characterized by an excellent air impedance matching strongly distinguishes itself by fulfilling all those requirements.

New heavy-duty diesel engine emission test regulations require even tougher emission limits verified with steady-state as well as transient test procedures, which are becoming increasingly important. The target of this paper is to describe the requirements and tasks for the fuel consumption measurement system and to discuss critical parameters which are essential for the layout of the fuel measurement system. The resulting fuel measurement system will be described and the performance ability will be demonstrated by measurement results and application examples. High absolute measurement accuracy of the fuel mass flow sensor, high fuel temperature control accuracy, appropriate fuel pressure control and fast time response of the complete fuel measurement system are all crucial factors needed to achieve repeatable specific fuel consumption values within 1 g/kWh and an overall time response of less than 300 ms.

Over the past few years, the fuel mass measurement gained in importance to record the consumed fuel mass and the specific fuel consumption [g/kWh] with high accuracy. Measuring instruments, such as positive displacement meters, methods based on the burette or the Wheatstone bridge mass flow meter measure either the volumetric flow and a temperature-dependant fuel density correction is necessary or they have old technology and therefore poor accuracy and repeatability. A new-generation Coriolis sensor featuring an ideal measurement range for engine test beds but still with flow depending pressure drop has been integrated in a fuel meter to ensure that no influence is given to the engine behaviour for example after engine load change. The new Coriolis meter offers better accuracy and repeatability, gas bubble venting and easy test bed integration. For returnless fuel injection systems the fuel system supplies the fuel pressure.