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The authors used a mass spectrometer to determine an SOF reduction mechanism of a diesel oxidation catalyst. The results indicate that SOF reduction lies in the catalytic conversion of high molecular organic matter to low molecular organic matter. And unregulated emissions are also reduced through this conversion. It is also found that the SOF reduction performance is highly dependent up on the condition of the wash coat. There is some limitation to improving diesel oxidation catalyst performance because of the sulfur content found in diesel fuel. Finally, the authors have determined what we think are the specifications of the presently best catalytic converter.

In order to meet increasing demands for safety and comfort in a vehicle compartment, automatic adjustment of seat, mirrors, steering wheel has been developed. The multiplex wiring system was constructed for the automatic adjustment of the cockpit elements to drivers preferred positions or to physique-matched settings based on ergonomic data. This paper describes the construction of the multiplex system and functions of automatic adjustment of the cockpit elements for comfortable driving position and better visibility.

This year (1989) Mitsubishi Motors Corp. introduced, on some models, a newly-developed Hydraulic Coupling Uint (HCU), by which 2WD vehicles can be converted into 4WD ones in the same way as done by a viscous coupling (VC). This HCU is similar in the configuration to a vane pump: the oil discharge is returned to the suction chamber through a number of orifices. The rotor and cam ring (housing) are respectively connected to the two shafts; either of the one with the front wheels and the other with the rear wheels. Accordingly, it works as a slip-sensitive differential like a VC while it has a merit of progressive and parabolic torque-response characteristic, which offers stronger traction and acceleration capability and also minimizes tight-corner braking. This paper discusses primarily the configurations, functions and test results of the HCU and also presents an overview on further development possibilities of the 4WD system.

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.

The need of lightweight vehicle design is motivated by the recent global trend of less fuel consumption and lower emission in vehicle. However in NVH development of vehicle, it becomes more difficult for the lightweight vehicle to reach low vibro-acoustic sensitivity than, for the heavy weight one to do so. Inthis environment, this paper describes about the practical finite element (FE) modeling of vehicle structure and acoustics, in order to predict "boom" response to powertrain excitation. The FE modeling process through validation and updating with experimental mode makes, the accumulation of considerable expertise for improving prediction accuracy, possible. FE analysis based on this modeling process is so useful for predicting "boom" levels up to 200 Hz. Using the result of FE analysis, structural optimization is executed in order to improve "boom" level of 80 Hz.

For meeting more stringent regulations to be imposed for reducing particulate matter (PM) in exhaust gas from diesel engines, it is required to improve performance of a trap system or other post-processing devices as well as fuel combustion efficiency of the engine itself. In the trap system, a trap filter is equipped to collect PM from exhaust gas. For continuous use of the trap filter, a regenerative processing must be carried out to remove PM by means of forced burning when a certain amount of PM has been trapped. The combustibility or burning characteristics of collected PM have a significant effect on the regenerative processing with an electric heater/burner. To clarify the combustibility of PM collected in the trap filter, we have examined the relationships between engine drive conditions (exhaust gas temperature), PM characteristics, and combustibility.

Auto-regeneration of diesel particulate traps, particularly combustion mode of soot in a wall flow filter with fuel additives, was investigated using a diesel engine of a light duty truck and truck itself. Soot burning in the trap and regeneration were observed under any engine operating condition including prolonged idling and stop-and-go driving at 0.18g metal/1 dosage of a mixture of copper and lead in the fuels. However, trap life was limited by ash clogging due to the metallic compounds. Although the influence of metallic additives on the environment was debatable, test results of the trap durability and calculations of soot burning based on the thermal ignition theory indicated that dosage and kind of fuel additives should be optimized in view of both trap life and reliability of soot burning.

With the intention of improving engine performance and emissions, the authors examined the influence of the method of initial fuel injection quantity reduction and of the injector configuration of a common rail fuel injection system on engine performance and exhaust emissions. Results showed that decreasing the nozzle hole diameter was an effective way to reduce the initial injection quantity without increasing black smoke. Compared to a three-way type injector, it was found that a two-way type injector can greatly reduce the amount of fuel leakage from the electromagnetic injector control valve and fuel consumption could be further improved by reduction of the driving loss. Furthermore, the increase of driving losses with higher injection pressure was small, and as a result, higher pressure injection was possible.

As the global environmental protection becomes the world consensus recently, the regulations of the fuel consumption and the exhaust gas have large effects on the performance and the fundamental structure of commercial vehicles. Especially the technology concerning "fluid" and "heat" has a close relationship with those issues. Owing to above circumstances, commercial vehicles such as large trucks and buses are forced to be designed near the limit of allowance. Furthermore, a rapid design is another requirement. However, though significant number of variations, i.e., cab configuration, wheel base, rear body configuration, engine specification, etc., are prepared, it is impossible to improve the performance of all those combinations by experiments which cost a lot. Accordingly, the quantitative prediction using computer will become indispensable at the beginning term of new car development.

If a torque converter clutch is allowed to slip to a minimal amount, engine torque can be transmitted through a transmission without torque variation problem, and also low fuel consumption is realized by putting the clutch in operation even at low engine revolution. Oil pressure applied to clutch is electronically feedback-controlled to keep clutch slip to a minimal amount. But this feedback system tends to become unstable by impairment of various factors of the system. This paper relates to the stability analysis of feedback system, and especially to the control method by which feedback system can be made stable even when µ-v characteristic of clutch facing material is impaired.

This paper describes the results of the study and research on ovate wire helical springs which have been jointly conducted by the members of the Japan Society for Spring Research consisting of the engineers from material suppliers, wire and spring producers and automotive manufacturers as well as researchers at Japanese universities. Attention is focused particularly on two types of wire cross sections, typical elliptical shape and Fuchs' egg-shape. Stresses on these two cross sections were analyzed by numerical calculations within the range of practical specification, and then the results have been compared with those of round wire spring. As a result, it has been found that the elliptical wire spring is superior to Fuchs- egg-shaped one for general application. Simple designing methods for the both types of wire helical springs have been developed based on the findings from the stress analysis.

Mitsubishi has developed the new, compact, water-cooled vertical type 2-cylinder diesel engine model K2AS and brought it to market in spring of '82. The K2AS is a small-sized engine of 451 cc total displacement and 10HP/3600 rpm maximum output. Its weight of 58 kg is light enough to use this diesel engine for various machines which have formerly been driven by gasoline engines. The well matched combustion chamber and injection system realize low fuel consumption, low noise and easy engine starting. High durability is also assured by various kinds of reliability evaluation. Features of K2AS are outlined below.

A particulate trap oxidizer system to reduce diesel particulate emissions has been developed. This system consists of a ceramic foam filter with an optimum volume, shape, and mesh number in terms of collection efficiency, pressure loss and particulate blow-off; a catalyst with a low activated-temperature for particulate incineration and with no sulfate formation during highway driving; and a regeneration system which prevents particulate overcollection during long-term continuous low-load/low-speed driving where it is difficult to achieve self-burning of particulates with a catalytic reaction. This paper describes the development of the particulate trap oxidizer system with these technologies and presents the results of practicability evaluations and 50,000-mile vehicle durability tests.

The major problems of the various mixture formation concepts for direct injection gasoline engines that have been proposed up to the present were caused by the difficulties of preparing the mixture with adequate strength at spark plug in wide range of engine operating conditions. Novel combustion control technologies proposed by Mitsubishi is one of the solution for these problems. By adopting upright straight intake ports to generate air tumble, an electromagnetic swirl injector to realize optimized spray dispersion and atomization and a compact piston cavity to maintain charge stratification, it has become possible to achieve super-lean stratified combustion for higher thermal efficiency under partial loads as well as homogeneous combustion to realize higher performance at full loads. GDI™ (Gasoline Direct Injection) engine adopting these technologies is developed. At partial loads, fuel economy improvement exceeding 30 % is realized.

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.

A flexible fuel vehicle (FFV) was evaluated through various tests for its potential as an alternative to the conventional gasoline vehicle. This paper presents the systems incorporated in the FFV and the test results. 50,000 mile emission durability tests were also performed and the potential of the FFV as a “Low Emission Vehicle” was assessed. As the result of extensive engineering work, we successfully developed a Galant FFV which exhibits very good durability and reliability. The emission control system which we have developed demonstrated that the vehicle has a good potential to comply with the California formaldehyde emission standard of 15 mg/mile. However, due to the large portion of unburnt methanol in the tail-pipe emissions, FFVs will have more difficulty than gasoline vehicles in meeting non-methane organic gas (NMOG) standards applicable to “Low Emission Vehicles”.

Beta Ti alloy valve spring retainers are newly developed for use in mass produced automobiles for the first time. Ti alloy valve spring retainers vith a weight saving of 42%, compared to steel retainers, have reduced the inertial weight of the valve train components by 6%. And this weight reduction has the benefit of increasing the upper limit of the engine speed, which improves the engine performance. Ti alloy valve spring retainers are cold forged by the conventional fabrication facilities for steel retainers, using Ti-22V-4Al (the beta Ti alloy) which possesses excellent cold workability in a solution treated condition. Oxygen surface hardening is applied to protect Ti alloy valve spring retainers from wear damage. In addition, aging treatment and shot blasting are performed to improve strength and stiffness of valve retainers.

A new combustion system - called MCA-JET- has been developed to improve combustion under the low speed, low load conditions typical of urban driving. Engines with this new system incorporate a special “jet valve”, in addition to the inlet and exhaust valves of the conventional combustion chamber, which directs air or a super-lean mixture towards the spark plug, and induces a strong swirling flow in the cylinder. This swirl persists during the compression and expansion processes, moves the mixture spirally and helps the flame to propagate. As a result, the combustion of lean mixtures, including those with exhaust gas recirculation, can be carried out rapidly and thus the fuel economy improved.

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.

It is well-known that double-mass torsional rubber dampers which have two masses and springs in parallel are effective for controlling torsional vibration characteristics over a wide range of engine speed. On the occasion of reliability estimation of the rubber dampers, it is important to consider generation of heat in the rubber due to torsional vibration. By predicting generation of heat at the designing stage, optimum design of the torsional rubber dampers can be achieved. By development and application of this prediction method, a new type double-mass damper was developed. It provided higher vibration control characteristics and reliability than conventional viscous dampers, and also it provided advantages in terms of noise, productivity and weight.