Realistic Emission Tests for Motorbikes, Mopeds and Quads

As part of an international project consortium, TU Graz has developed new measurement techniques and methods to measure emissions from category-L vehicles in realistic operation and to determine corresponding limit values.

The emissions scandal in the automotive industry that came to light in 2015 has set many things in motion. Last but not least, the discussion about the need for realistic tests for vehicles in order to correctly determine their pollutant emissions instead of just testing on test rigs. Such tests and the applicable emission limits are now required by law for cars, but not for so-called category-L vehicles (mopeds, motorbikes, tricycles and quads). As part of the "LENS" project (L-vehicles Emissions and Noise mitigation Solutions) funded by the European Commission, Graz University of Technology (TU Graz), as part of an international consortium, has now developed corresponding test procedures and the necessary test equipment. The project results will serve the legislator as a basis for future decisions, provide law-enforcement agencies with the equipment to detect limit violations and vehicle manipulation, and allow manufacturers to adapt their fleets accordingly.

Worldwide unique methodology and technology

"The measurement methods developed for passenger cars in recent years are not applicable to the much more dynamic category-L vehicles," says Stephan Schmidt from the Institute of Thermodynamics and Sustainable Propulsion Systems at TU Graz. "So, we had to develop our own measuring methods, which also included the development and further development of suitable measuring devices that are small and light enough to be used on motorbikes and mopeds. The measurement methodology and technology developed and the emissions data collected are unique worldwide." A total of 15 partners are involved in the project consortium, including nine research institutions, four manufacturers of two-wheelers and producers of measurement technology.

As part of "LENS", the The Institute of Thermodynamics and Sustainable Propulsion Systems and the Institute of Electrical Measurement and Sensor Systems were responsible for developing and creating the measurement methodology and some of the measurement technology for all’In addition to the creation of route profiles suitable for tests with all category-L vehicle types, the miniaturisation of the measurement technology was a particular challenge. While equipment weighing more than 60 kilograms does not play much of a role in a car, it makes a huge difference on a motorbike and especially on mopeds - both in terms of pollutant emissions and riding characteristics. For motorbikes, the necessary reduction in size and weight was achieved by involving an external partner. For the weaker vehicles, a consortium partner contributed small measuring devices which, although not as accurate, provide good reference values.

A mix of all classes and driving styles

Creating the route profiles was challenging because a scooter with just a few horsepower is completely different to ride compared with a motorbike with over 100 horsepower. In the end, the researchers found a good mix that included both sporty and hilly sections and took different vehicle classes and driving styles into account. However, the wide range of drive systems, drive outputs, installation space ratios and vehicle masses required a measurement methodology adapted to the subclasses. Precise measurement of the exhaust gas mass flow is crucial for calculating emissions. With small-volume single-cylinder engines, however, mass flow measurement using conventional methods is difficult. However, the model-based method for mass flow calculation developed at TU Graz and used in the LENS As the vehicles in the lower performance classes can be fully extended on the test bench, the researchers were able to create a model based on the test bench data, from which the mass flows during the journey can be calculated. This enabled the team to obtain usable emission data from the reference values of the small measuring devices.

"The many engine concepts and performance classes in the L-vehicle sector are a challenge when it comes to finding standardised test methods that realistically measure noise and exhaust emissions," says Stephan Schmidt. "In the LENS project, however, we have succeeded in doing this and, together with our consortium, we have created the technical basis for manufacturers, legislators and law enforcement agencies to be able to assess vehicles on the basis of realistic values in future. This will contribute to a significant reduction in pollutant emissions from the category-L vehicle fleet."

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