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To reduce friction is required to improve engine fuel economy. This study aimed to reduce piston skirt friction, which is a major factor in engine friction. ‘Soft skirt’ is a trendy item in recent gasoline engines, which can improve skirt sliding condition by larger deformation when the piston is pressed to the liner. The effect is confirmed by friction measurement and oil film observation, using prototype pistons. And also one major factor of the effect is clarified that not only side force but also cylinder pressure causes effective deformation of the skirt to create thick oil film at early combustion stroke.

Global environment protection, Co2 emission reduction and so on, is an important problem in automotive industry. An Electric Vehicle (EV) production is one of policies. Co2 emission of EV is lower than Internal Combustion Engine (ICE), petrol and diesel engine. On the other hand, customer's needs for the comfort on driving increase year after year. So it's an important factor for new car performance. Generally speaking, it's thought that the noise and vibration performance of EV have the better of ICE performance. However the aerodynamic noise and road noise contribution for interior noise in EV rise in comparison with ICE, and moreover the sound quality change by new noise component of the motor noise. Therefore new sound evaluation method is needed for EV. So this paper demonstrates each noise component contribution in EV by new noise separation technology, and show the comparison result with EV and ICE.

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.

An efficient cooling system will ensure the reliability of the EV/HEV (Electric Vehicle/Hybrid Electric Vehicle) battery system and extend their lifetime. In order to shorten design period or increase design iterations, a high-speed and high-precision prediction method for cooling is indispensable. For models, such as Mitsubishi i-MiEV, which use fresh air to cool batteries in the battery pack, a transient approach based on loosely coupled method is developed to predict temperature change of batteries. The results by our new approach are in good agreement with the experimental data. Moreover, for the EV/HEV using circulated air to cool its batteries, a second approach is also developed, which can predict the temperature variations of both EV/HEV batteries in the battery pack and the cooling air.

Two-stage hybrid combustion for a 6-stroke gasoline direct injection SI engine is a new strategy to control the ignition of the HCCI combustion using hot-burned gas from the stratified lean SI combustion. This combustion is achieved by changing the camshafts, the cam-driven gear ratio and the engine control of a conventional 4-stroke gasoline direct injection engine without using a higher compression ratio, any fuel additives and induction air heating devices. The combustion processes are performed twice in one cycle. After the gas exchange process, the stratified ultra-lean SI combustion is performed. The hot-burned gas generated from this SI combustion is used as a trigger for the next HCCI combustion. After gasoline is injected in the burned gas, the hot and homogeneous lean mixture is recompressed without opening the exhaust valves. Thus the HCCI combustion occurs.

The gasoline direct injection engine starts significantly faster than a conventional engine. Fuel can be injected into the cylinder during the compression stroke at the same time of cranking start. When the spark plug ignites the mixture at the end of compression stroke, the engine has its first combustion, that is, the first combustion occurs within 0.2 sec after the start of cranking. This unique characteristic of quick startability has realized a idle stop system, which enables drivers to operate the vehicle in a natural manner.

The Mitsubishi GDI engine has adopted a pair of upright intake ports, to induce a rotating in-cylinder flow, reverse tumble, and control air fuel mixing with this flow. The port design of the GDI engine was optimized for achieving a high intensity of the reverse tumble while maintaining a high charge coefficient, by means of modeling of in-cylinder flow and experiment with a steady flow rig. First of all, the ideal design of the upright ports was discussed. It was found that for enhancing the reverse tumble, it is more effective to arrange a pair of the ports parallel, than to arrange them convergent. The parallel arrangement leads to the smoother flows passing through the intake sides of the intake valves, and then descending on the cylinder liner, that is turning toward the rotation direction of the reverse tumble, because of less impingement of the flows through a pair of the valves.

In the next few years, the USA, EU, and Japan plan to introduce very stringent exhaust emissions regulations for heavy–duty diesel engines, in order to enhance the protection air quality. This builds upon the heavy–duty diesel engine exhaust emissions regulations already in effect. At the same time, improvement in fuel consumption of heavy–duty diesel engines will be very important for lowering vehicle operating costs, conserving fossil fuel resources, and reduction of CO2 (greenhouse gas) levels. This paper presents a detailed review of a quiescent combustion system for a heavy–duty diesel engine, which offers breakthrough performance in terms of the exhaust emissions – fuel consumption trade–off, compared with the more conventional swirl supported combustion system. This conclusion is supported by experimental results comparing quiescent and swirl supported versions of various combustion system configurations.

In this study, the oxidation stability, soot dispersancy, antiwear performance, and friction-reducing capability of friction modifiers (FMs) were evaluated, and an SAE 5W-30 fully synthetic oil with MoDTC type FMs was developed for heavy-duty diesel engines. In several engine tests, it was confirmed that the developed oil can double the oil drain interval in comparison with API CD SAE 30, even when EGR is applied, and improves the fuel efficiency.

Injection rate control is an important capability of the ideal injection system of the future. However, in a conventional Common-Rail System (CRS) the injection pressure is constant throughout the injection period, resulting in a nearly rectangular injection rate shape and offering no control of the injection rate. Thus, in order to realize injection rate control with a CRS, a "Next- generation Common-Rail System (NCRS)" was conceptualized, designed, and fabricated. The NCRS has two common rails, for low- and high-pressure fuel, and switches the fuel pressure supplied to the injector from the low- to the high- pressure rail during the injection period, resulting in control over the injection rate shape. The effects of injection rate shape on exhaust emissions and fuel consumption were investigated by applying this NCRS to a single- cylinder research engine.

The 4M5 series of four-cylinder, in-line, direct-injection diesel engines has been released by Mitsubishi Motors Corporation for light and medium-duty trucks and buses. Featuring an updated structure and reflecting the employment of state-of-the-art technology in the design of every component, the new engine series offers high reliability and compact dimensions. Moreover, the new series well meets contemporary demands for high performance, low noise, and clean combustion.

Spray motion visualization, mixture strength measurement, flame spectral analyses and flame behavior observation were performed in order to elucidate the mixture preparation and the combustion processes in Mitsubishi GDI engine. The effects of in-cylinder flow called reverse tumble on the charge stratification were clarified. It preserves the mixture inside the spherical piston cavity, and extends the optimum injection timing range. Mixture strength at the spark plug and at the spark timing can be controlled by changing the injection timing. It was concluded that reverse tumble plays a significant role for extending the freedom of mixing. The characteristics of the stratified charge combustion were clarified through the flame radiation analyses. A first flame front with UV luminescence propagates rapidly and covers all over the combustion chamber at the early stage of combustion.

Several different steel sheets were tested for energy absorption, using hat square columns and dynamic crash testing. Results indicate that steel sheets containing large volume fraction of retained austenite have relatively high energy absorption. The relationship between retained austenite and energy absorption was analyzed. These special steel sheets have already been successfully used for production body parts, such a front-side-member, without difficulties arising in volume production.

Mitsubishi Motors Corporation (MMC) has developed a new V configured 8 cylinder turbocharged and intercooled diesel engine (8M22T1) for the heavy-duty truck market. The engine is one of the first in its class to feature a common rail fuel injection system. This advanced engine management system was selected to meet the challenges of ever tightening emission regulation, specifically in the areas of smoke and noise. The 8M22T1 embodies a number of design innovations which have resulted in significant improvements in performance, fuel economy, durability and reliability.

In this study three EGR methods were applied to a 12 liter turbocharged and intercooled Dl diesel engine, and the exhaust emission and fuel consumption characteristics were compared. One method is the Low Pressure Route system, in which the EGR is taken from down stream of the turbine to the compressor entrance. The other two systems are variations of the High Pressure Route system, in which the EGR is taken from the exhaust manifold to the intake manifold. One of the two High Pressure Route EGR systems is with back pressure valve located at downstream of the turbine and the other uses a variable geometry(VG) turbocharger. It was found that the High Pressure Route EGR system using VG turbocharger was the most effective and practical. With this method the EGR area could be enlarged and NOx reduced by 22% without increase in smoke or fuel consumption while maintaining an adequate excess air ratio.

Passenger cars with sunroofs sometimes experience a low frequency pulsation noise called “wind throb” when traveling with the roof open. This “wind throb” should be suppressed because it is an unpleasant noise which can adversely affect the acoustic environment inside a car. In this paper, 3-dimensional numerical flow analysis is applied around a car body to investigate the wind throb phenomenon. The computational scheme and the modeling method of the car body is first described. A flow visualization test in a water tunnel was completed for the simple car body shape to compare against the numerical procedure. The numerical and the visualized results compared well and the numerical simulation method employed was considered to be a reliable tool to analyze the wind throb phenomenon. Calculated results of pressure and vorticity distribution in the sunroof opening were analyzed with the spectrum of pressure fluctuation at the sunroof opening with and without a deflector.

In this study a new water injection system was applied to an 11 liter naturally aspirated DI diesel engine in order to reduce exhaust emissions. In this system, the water and fuel were arranged in the injection nozzle during the time between injections as fuel, water and then fuel. The fuel and water were then injected into the cylinder in that order. The tests were conducted at several engine operating conditions from the Japanese 13 mode test cycle to clarify effects of water injection on exhaust emissions and fuel consumption. The results showed that NOx reduction was directly proportional to the relative amount of water injection, regardless of engine speed and load. By using the optimal relative amount of water injection at each engine operating condition, total NOx and particulate matter (PM) in the Japanese 13 mode test cycle were reduced by 50% and 25%, respectively, without a fuel consumption penalty.

We have developed a tappet with a cam lobe contacting tip made of a hard sintered material whose base material is cobalt, which adheres less to the steel of camshafts, and which also contains fine particles of tungsten carbide and chrome carbide. We have established a new evaluation method to access wear resistance performance of the tappet. It enables us to measure directly the friction force generated between the cam lobe and tappet and to evaluate anti-scuffing performance with high accuracy because we can clarify the time, load and cam angle at which scuffing occures.

This paper presents a new torque distribution system-“Right/Left Torque Control System”, aimed at improving a vehicle's cornering properties by using yaw moment control. The torque transfer mechanisms of this system have been analyzed. Also, a yaw moment control algorithm using yaw rate feedback control has been designed. Next, vehicle cornering properties were evaluated using numerical simulation developed from data taken from an actual vehicle. As a result, improvements were achieved in the maneuverability and stability of a vehicle during cornering.

To reduce diesel engine noise that is induced mainly by main bearing impact forces, two types of low noise concepts of basic crankcase structures were studied. One is the “Isolated Skirt Type”, which has the feature to suppress vibrations of engine surface by separating the crankcase skirt from the main bearing caps. The other is the “Bed Plate Type”, which embodies the feature to suppress vibrations by stiffening the lower part of crankcase by adopting a bed plate design. Dynamic characteristics of both prototypes were investigated by means of experimental modal testings such as double pulse laser holography system and impulsive hydraulic excitation test rig which simulates the exciting force of combustion gas pressure in cylinder. As the result of many experimental tests, it was concluded that the “Bed Plate Type” was advantageous over the “Isolated Skirt Type” in terms of engine noise reduction.