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The EURO4 standard has been enforced since the year 2017 for European quadricycle. The vehicles are regulated upper limit of unladen weight and engine displacement, in addition to the exhaust emissions and the net power. In order to meet those regulations, the engine for European quadricycle is demanded low exhaust emissions and light weight. Further, it is required to be achieved good drivability, low fuel consumption, low noise and more compact. We introduce technologies to meet demand for European quadricycle in compliance with EURO4. The limit values of exhaust emissions have been strengthened in EURO4 standard compared to the previous one. As devices to improve the exhaust emissions, the exhaust-after-treatment devices and the common rail injection system are well known, whereas those devices make engine systems heavier. In addition, to satisfy high torque at low speed for better drivability, larger displacement is effective.

In this paper, a friction estimation method using a tire vibration model is proposed. It is based on the frequency characteristics of the wheel speed vibration which are related to the tire-road friction. The recursive least squares and the instrumental variable method are applied for online estimation. The experimental result shows that the proposed method applied to free rolling tire detects friction change from dry asphalt to iced road at constant speed without braking, accelerating or cornering.

In the consideration of safety to health, many countries have recently been enforsing regulations on the use of asbestos. To keep abreast of this trend, it has become necessary to replace the gasket materials currently used in the cases and the covers of motorcycle engines with non-asbestos materials. The gaskets used in motorcycles are subjected to extremely severe sealing loads and temperature in the small and high performance engines. They are required to have excellent sealability and creep relaxation characteristics at high temperature. Under such conditions, it is extremely difficult to substitute non-asbestos materials for asbestos which has superb material characteristics such as higher heat resistance and greater aspect ratio (length of fiber/dia.).