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The European emission legislation for two-wheeler vehicles driven by engines of ≤ 50 cm₃ is continuously developing. One of the most important issues in the near future will be the finalization of the European Commission's proposals for future steps in the emissions regulations as well as the verification of the impacts of current standards on the market. To have a basis for the discussion about these topics, the Association for Emissions Control by Catalyst (AECC) with the Institute for Internal Combustion Engines and Thermodynamics of Graz University of Technology (IVT) carried out an extensive test program to show the actual emission situation of state-of-the-art mopeds including mass and number of particulate matter as well as unregulated gaseous components. One of the main goals of these tests was to measure exhaust emissions without any modifications to the engines of standard production vehicles available on the European market.

The Institute for Internal Combustion Engines and Thermodynamics, Graz University of Technology, has presented several applications of its 2-stroke LPDI (low pressure direct injection) technology in the previous years ([1], [2], [3]). In order to improve the competitiveness of the 2-stroke LPDI technology, an air cooled 50cm3 scooter application has been developed. All previous applications have been liquid cooled. This air cooled application demonstrates the EURO 4 (2017) ability of the technology and shows that the 2S-LPDI technology can also be applied to low cost air-cooled engines. Hence, the complete scooter and moped fleet can be equipped with this technology in order to fulfil both the emission standards and the COP (conformity of production) requirements of Euro 4 emission stage. The paper presents the Euro 4 Scooter results and describes the efficient conversion process of the existing carburetor engine to the LPDI version.

Affordable, efficient and durable catalytic converters for the two and three wheeler industry in developing countries like India are required to reduce vehicle emissions and to maintain them at a low level and therefore to participate in a cleaner and healthier environment. A new generation of metallic substrates with structured foils for catalytic converters has been proven capable of improving conversion behavior even with smaller catalyst size. Specially developed foil structures which transform a laminar exhaust gas flow into a turbulent one, which significantly improve exhaust gas mixing behavior in the catalyst. This publication will deal with the analysis of different metallic substrate foil structures for the catalyst conversion performance for the leading “state of the art” four stroke 150 cm3 motorcycle technology developed for the Asian market.

More and more stringent emission legislation is implemented in the world wide market of motorcycles leading to higher product costs. But not every market is ready for high technological levels. Therefore the main topic of interest is: “Will a small one cylinder motorbike engine need an electronic device for fuel metering or is it possible to use standard carburetors in combination with some smart but simple ideas, to fulfil EU III cold start emission regulations?” The described ideas deal with a novel secondary air supply, an improved cooling system and simple NOx reduction methods, always paying attention to the performance and driveability of the vehicle. After describing the prototype design of the engine modifications, the achievable results with their pros and cons are discussed. Online recorder measurements give interesting emission plots of HC, CO and NOx. The homologation measurement results point out the obtainable values of the limited emissions.

Due to the small number of two wheelers in Europe and their seasonal use, their contribution to the total emissions has been underestimated for a long time. With the implementation of the new emission regulation 168/2013 [3] for type approval coming into force 2016, the two wheeler sector is facing major changes. The need to fulfil more stringent emission limits and the high demand on the durability of after treatment systems result in an engine control system that is getting more complex and therewith more expensive. Especially the low cost two wheelers with small engine capacities will be affected by increasing costs which cannot be covered by the actual competitive product price. Therefore, new vehicle concepts have to be introduced on the market. A vehicle concept of a plug in hybrid electric city scooter with range extender as well as the range extender itself have already been published in SAE Papers 2011-32-0592 [1] and 2012-32-0083 [2].

Modern small capacity motor scooters make high demands on a trendy vehicle design in combination with a customer friendly handling and multifarious storage space. In addition, increasing engine performance characteristics and high requirements on the vehicle weight call for the development of new vehicle frame concepts. Considering lightweight construction and strength durability, the new concepts are also due to fulfill the boundaries of a low cost production. The driving behavior of a scooter is directly influenced by the interaction of the suspension components, the mounting system of the drive unit and the stiffness of the frame. The present publication treats an assessment of different frame types in the 50cc scooter class by tests and simulation with the target to formulate key data regarding the solidness and stiffness characteristics. Based on these data collection a complete new frame concept has been designed and revised by calculation.

Usually the power output of 50 cm₃ two wheelers is higher than necessary to reach the maximum permitted vehicle speed, making engine power restriction necessary. This publication deals with different power restriction strategies for four-stroke engines and their effect on exhaust emissions. Alternative power limitation strategies like EGR and leaning were investigated and compared with the common method of spark advance reduction to show the optimization potential for this certain engine operation conditions. From these tests, a substantial set of data showing the pros and cons in terms of emissions, combustion stability and fuel economy could be derived for each speed limiting technique.

Small engines for non-automotive and two wheeler applications have a reduced number of sensors. For fulfilling emission regulations a cost effective way is an enhanced use of standard sensors in order to obtain more information from the existing sensors. The delivered information can then be used for an on-board diagnosis. Moreover, it is important to control the quality of the product during engine production; therefore an end-of-line cold engine test is often made. With this measure it is possible to detect faults, wrong tolerances or assembly in order not to deliver faulty engines to the customers. In this paper, an enhanced use of sensors for fault detection will be discussed. It is possible to obtain more information from the signal or to use the sensor for detecting other parameters. For extracting information signal analysis methods will be used with focus on the computational power need since the ECU performance is limited.

State of the art technologies of 2 and 4 stroke engines have to fulfill severe future exhaust emission regulations, with special focus on the aspects of rising performance and low cost manufacturing, leading to an important challenge for the future. In special fields of applications (e.g. mopeds, hand held or off-road equipment) mainly engines with simple mixture preparation systems, partially without exhaust gas after treatment are used. The comparison of 2 and 4 stroke concepts equipped with different exhaust gas after treatment systems provides a decision support for applications in a broad field of small capacity engine classes.

Thanks to its unsurpassed power-to-weight ratio, its low package space and low-maintenance design, the loop-scavenged two-stroke engine with conventional mixture preparation is still being used in some sectors of vehicle engineering, such as boat drives, snow mobiles and motor scooters, as well as in hand-held applications. To maintain the potential of the 2-stroke engine for the future it is necessary to take adequate steps against the system-dependent disadvantage of the simple 2-stroke engine, namely that of higher emissions compared to 4-stroke engines. One possible solution is gasoline direct injection. Its more frequent use will increase the production numbers, making it an interesting technology even in the above-mentioned cost-sensitive applications. The current report presents various concepts of direct injection in 2-stroke engines, from air-assisted injection through to high-pressure direct injection, and compares them with traditional techniques of mixture formation.

Charge dilution in gasoline engines reduces NOx emissions and wall heat losses by the lower combustion temperature. Furthermore, under part load conditions de-throttling allows the reduction of pumping losses and thus higher engine efficiency. In contrast to lean burn, charge dilution by exhaust gas recirculation (EGR) under stoichiometric combustion conditions enables the use of an effective three-way catalyst. A pre-chamber spark plug with hot surface-assisted spark ignition (HSASI) was developed at the UAS Karlsruhe to overcome the drawbacks of charge dilution, especially under part load or cold start conditions, such as inhibited ignition and slow flame speed, and to even enable a further increase of the dilution rate. The influence of the HSASI pre-chamber spark plug on the heat release under EGR dilution and stoichiometric conditions was investigated on a single-cylinder gasoline engine.

In consideration of the fact that in extreme Enduro competitions two-stroke motorcycles are still dominating, the Institute of Internal Combustion Engines and Thermodynamics, Graz University of Technology, with a long tradition in two-stroke technology, has developed a new 300 cm3 two-stroke motorcycle engine. The 2-stroke LPDI (Low Pressure Direct Injection) technology was originally developed for the 50 cm3 Scooter and moped market in Europe. In 50 cm3 applications the LPDI technology fulfils the EURO 4 emission standard (2017) [1]. In a next step the LPDI technology was applied to a 250 cm3 Enduro engine demonstrator vehicle. Based on the results of the demonstrator, a complete new high performance 300 cm3 engine was developed. The development of this new engine will be described in this publication. Some interesting aspects of the layout with 3D-CFD methods and also 1D-CFD simulation to optimize the exhaust system by DoE methods are discussed in the paper.

The new generation of metallic substrates for catalytic converters used in the two and three wheeler industry is capable of improving conversion behavior even with smaller catalyst size. The lowering of production costs due to less use of precious metal is possible. This novel technological application in motorcycle vehicle class improves exhaust emission performance and introduces a new competitive product on the market. Specially developed foil structures, which transform a laminar exhaust gas flow to a turbulent one, significantly improve exhaust gas mixing behavior in the catalyst. This publication is dealing with the analysis of different metallic substrate foil structures for the catalyst conversion performance and the light-off characteristics for the leading state of the art four stroke 150 cm3 motorcycle technology developed for the Asian market.

Future emission regulations for two wheeler vehicles driven by small capacity engines will include the cold start characteristics and the durability behavior. [1] Based on the European homologation cycle ECE R47 and an additional cold start test cycle, a number of scooters driven by 50cc engine concepts in combination with different exhaust gas after treatment strategies have been analyzed and evaluated. The test series have been performed with the help of a CVS measurement system according the European homologation instruction and in addition with the help of an online emission recorder measurement.

Looking at the market for 2-wheelers driven by small capacity four stroke engines, it turns out that the legislation for exhaust emissions is mostly combined with a regulation of vehicle speed. Most of the vehicles in this category are still driven by engines equipped with carburetors which, unlike fuel injection systems, do not give the possibility to cut off fuel metering when high speed is achieved. When a carburetor is applied with a simple ignition unit, a reduction of spark advance is the only way to ensure correct vehicle speed, but there are a lot of disadvantages in terms of exhaust emissions and fuel economy coming up with this method of engine power restriction. This leads to the idea of using exhaust gas recirculation (EGR) to reduce engine power when necessary.

More and more restrictive regulations, as the pending Euro3 emission legislation, demand for a lowering of exhaust emissions of two stroke engines. The reduction of scavenge losses is one of the key requirements for the development of two-stroke engines. Besides it is important to maintain the excellent torque and power behavior of the two stroke units. This publication gives a summary of previous and present development results of test bench and chassis dynamometer measurements and of 3D CFD simulations. All these results are targeted on a reduction of the scavenge losses and therewith HC-emissions. Therefore the focus is put on different injection strategies, such as semi-direct and air-assisted injection. Additionally, the potential of the high pressure gasoline direct injection is presented, even if this technology is still too expensive for the small capacity engine market, e.g. the European 50 cc scooter class.

Increasingly stringent emission regulations force manufacturers of two wheelers to develop low emission motorcycle concepts. Especially for small two-stroke engines with symmetrical port timing structure, causing high HC-emissions due to scavenge losses, this is a challenging demand that can only be met with alternative mixture formation strategies and by intensifying the use of modern development tools. Changing from EU4 to EU5, emission legislation will not only have an impact on the improvement of internal combustion but will also drastically change the after-treatment system. Nowadays, small two-stroke engines make use of a simple carburetor for external mixture preparation. The cylinders are scavenged by air/fuel mixtures. Equipped with exhaust gas after-treatment systems, such as secondary air with two or three catalytic converters, the emission limits for EURO 4 homologation can be achieved with carbureted engines.