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Structural attenuation of a running diesel engine measured by a new technique showed a constant value regardless of engine speeds. It was verified by this result that structural attenuation is a physical quantity unique to the structure of each engine and, therefore, a good indicator for evaluation of low noise engine structure. In addition, a hydraulic excitation test rig was devised to measure structural attenuation directly and to make effective use of it for noise reduction. Based on the accurate measurements by the excitation test rig, modal analysis and system simulation were conducted for implementation of countermeasures against noise.

Vulcanized rubber hoses are difficult to recycle and have a complicated manufacturing process. Recently, we have developed the vacuum hose for engine control out of thermoplastic elastomers. As a result of this development, scrap material from the manufacturing process can be recycled and, in addition, about a 30 percent weight reduction and a 20 percent cost reduction are achievable by virtue of the lower specific gravity and by the more simplified manufacturing process. In order to assess the feasibility of using thermoplastic elastomers for vacuum hoses, we developed a heat aging simulation test method. This was achieved by first investigating the actual vehicle environmental conditions of currently used vacuum hoses by retrieving and examining these hoses from used vehicles. We then extrapolated what the condition of such hoses would be after being subjected to heat aging for 200,000 km of service in an actual vehicle, and applied this calculation to our newly developed hoses.

Mud adhesion to the rear surfaces of trucks, vans and buses causes troublesome results such as aesthetic degradation, hindered rear view and laborious washing. To raise the product value of trucks and buses, it is important to develop effective measures for suppressing such mud adhesion. In this research the authors first clarified the mechanism of mud adhesion through flow visualization tests. Then, wind tunnel tests were performed to predict the effects of various countermeasures, and prospective ones were put under actual driving tests to verify their effects. The following measures were found effective in suppressing mud adhesion. (1) Aerodynamic improvement by attaching corner vanes to the upper and side edges of the rear surface. (2) Blocking road splash with a slanted plate under the truck and close to the base.

The 4-stroke SI engine offers better performance if its valve events can be varied depending on the operating conditions. Some engines in production are therefore incorporated with variable valve timing (VVT) mechanisms. All of such mechanisms available today however are for two-mode change-over between low-and high-speed operations. To achieve even better output and fuel economy, a new multi-mode VVT mechanism has been developed, featured by a unique hydraulic device for three-mode change-over as follows: Deactivate both intake and exhaust valves Select low-speed cam with moderate lifts and short durations Select high-speed cam with high lifts and long durations This mechanism enables shutting off unnecessary cylinders during low-speed cruise, or select optimum valve events during WOT acceleration over the entire engine speed range.

Aerodynamic drag reduction is one of the most important aspects of enhancing overall vehicle performance. Many car manufacturers have been working to establish drag reduction techniques. This paper describes the development process of a new small speciality car which achieved coefficient of drag(CD) of 0.25. A description of the test facilities and the systems used for developing the aerodynamic aspect of the car are also introduced briefly.

The high-temperature durability of 85 mm tip diameter silicon nitride ceramic radial turbine rotors was evaluated with a hot gas spin test rig. The rotors withstood up to a turbine tip speed of 700 m/s at TIT of 1300°C under partially loaded conditions and 570 m/s at TIT of 1300°C under fully loaded conditions, respectively. The material of the rotors was a post-HIPed silicon nitride. The basic fatigue properties of the material were measured at high temperatures. In the hot gas spin test, the temperature and stress distributions at the turbine blade were calculated with a finite element method. The results of the hot-gas spin test are discussed by means of a failure prediction analysis on the basis of the Weibull statistics.

Mitsubishi Motors Corporation succeeded in mass production of the electric vehicle “i-MiEV” which features leading-edge technologies epitomized by lithium-ion battery. The EV was released into the Japanese market in July 2009 and the European market in January 2011. In order to be used all over the world, the EV has to be practical and durable even under severe weather of extremely cold or extremely hot regions. In this paper we report some results of the tests conducted under extremely cold weather as well as extremely hot weather. From the test results the validity of the vehicle control system and the practicality of the EV are verified.