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There has been a growing need to develop more compact automatic transmissions with a greater number of speeds for better fuel economy and better driveability. This study investigated a method for determining suitable planetary gear trains for today's transmissions. A computer program has been developed for application to five-speed transmissions consisting of two planetary gearsets. By analyzing various gear train possibilities, the program can identify which gearsets are suitable for different conditions, including the number of speeds, the number of binding elements, topological suitability and other factors.

The engine cooling system is required to provide much higher performance today owing to the improved power output of engines and the trend toward a more compact engine compartment. For front engine/rear drive vehicles equipped with a fluid coupling drive fan, one of the main problems that must be dealt with is the rise in coolant temperature during idling. This paper presents a new method to simulate the engine coolant temperature under idling condition, and an improved engine cooling system that features a totally redesigned fan blade for maximum efficiency. This new system, consisting of a high performance cooling fan shroud and coupling, achieves a substantial noise reduction and contributes to fuel economy and power output improvements.

This paper presents a new-generation, lightweight, 3-liter V6 engine that has been developed for use in the next Nissan Maxima. The distinctive features of this new engine, VQ30DE, is its compact, lightweight design and excellent fuel economy. The basic construction of the engine is characterized by its 60-degree V6 configuration, chain-driven DOHC and high-pressure die cast aluminum cylinder block. A two-way cooling system was adopted with the aim of shortening the warm-up time of the cylinder liners. The new engine has been designed to comply with the tougher emission standards, the OBD-II requirements and California's new evaporative emission standard.

A new high-performance and lightweight TiA1 intermetallic compound exhaust valve has been developed. The TiA1 valve can improve power output and fuel economy by contributing higher engine speeds and a reduction in valvetrain friction. It was achieved by developing a Ti-33.5A1-0.5Si-1Nb-0.5Cr (mass%) intermetallic compound, a precision casting method for TiA1 that provides a low-cost, high-quality process, and a plasma carburizing technique for assuring good wear resistance on the valve stem end, stem and face.

Fuel economy can be improved by reducing engine displacement, thanks to the resulting smaller friction losses and pumping losses. However, smaller engines frequently operate at high-engine speed and high-load, when pressure on the accelerator increases during acceleration and at high speed. To protect exhaust system components from thermal stress, exhaust gas temperature is reduced by fuel enrichment. To improve fuel economy, it is important to increase the frequency of stoichiometric operation at high-engine speed and high-load. Usually, the start timing of fuel enrichment is based upon temperature requirements to protect the catalyst. In the high-engine speed and high-load zone, the threshold temperature of catalyst protection is attained after some time because of the heat mass. Therefore, stoichiometric operation can be maintained until the catalyst temperature reaches the threshold temperature.

A key factor influencing the performance of a hybrid electric vehicle (HEV) is how the engine and motor-generator (MG) are combined with the vehicle. There have been several types of combinations such as power transfer by using the mechanical transmission of conventional vehicles or the electrical transmission originally designed for HEVs. The objectives of this research were to clarify fuel economy characteristics according to the type of power transfer system used and to identify the requirements for MG system development by analyzing MG operation conditions in each power transfer mode. HEV systems for passenger car use were modeled on the basis of a functional classification. Simulations were conducted using the characteristics of the power transfer systems as parameters to evaluate fuel economy tendencies under several driving modes. The mechanism of the fuel economy tendencies was then analyzed to evaluate quantitatively the effect of each power transfer system on fuel economy.

In order to significantly reduce NOx levels by EGR (Exhaust Gas Recirculation), while maintaining good fuel economy and driveability, the EGR flow rate must be properly and accurately controlled under a variety of engine operating conditions. Toward this objective, a new EGR control system was developed. It utilizes a carburetor venturi vacuum for a stable reference signal that represents the engine operating condition and it controls the EGR flow rate by using a feedback principle to obtain sufficient flexibility compatible with several different engines. Its control characteristics were mathematically analyzed. And it has also been confirmed that the system can automatically compensate for the drift in EGR characteristics. This EGR control system has been utilized in Nissan’s emission control systems in order to comply with the 1978 Japanese Emission Standards and the 1980 U.S. Federal and California Emission Standards.

The Inter-Industry Emission Control (IIEC) Program included the thermal reactor as one of the effective ways of oxidizing HC and CO in the exhaust system. However, this was accompanied by very substantial fuel economy penalties, especially in the case of small engine-low emission concept vehicles. Starting with a new concept aimed at obtaining the HC/CO oxidizing trigger temperature in the thermal reactor by modifying engine settings, the authors arrived at an economical technique of matching the thermal reactor to the engine.

An electronically controlled closed-loop carburetor system has been developed for production application in Datsun car models. Providing a means of complying with Japanese Emission Standards, this design features the electronic control of carburetor supplied fuel with significantly improved emission performance and fuel economy. Technological advances include the noteworthy compensation of oxygen sensor output variations and improved transient emission.

Three Japanese automobile manufacturers-Mitsubishi Motors Corp., Nissan Motor Co., Ltd., and Toyo Kogyo Co., Ltd.-have been making efforts over the past three years to design and develop effective thermal reactor-exhaust gas recirculation and catalytic converter systems suitable for small engines. The work is being done by members participating in the IIEC (Inter-Industry Emission Control) Program, and the exhaust emission levels of the concept vehicles developed by these companies have met the goal established by the IIEC Program at low mileage. Each system, however, has a characteristic relationship between exhaust emission level and loss of fuel economy. Much investigation is required, particularly with respect to durability, before any system that will fully satisfy all service requirements can be completed. This paper reports the progress of research and development of the individual concept vehicles.

A new 2.0 liter 4-cylinder gasoline engine has been designed and developed for light weight front-wheel drive vehicles. In developing this new engine, the major target was to improve fuel economy, and this was achieved by minimizing the engine weight, reducing mechanical friction loss and improving combustion efficiency. Major problems that had to be solved included assuring the durability of component parts, and reducing the noise and vibration caused by minimizing the weight of the engine structure. The basic concept of the Nissan NAPS-Z engine, which is fast burn combustion with a two-point ignition system, has been used and further improved in the new engine. To develop this new engine, all component parts were newly designed using computer design analysis techniques, and thecked by extensive testing. This paper describes the design characteristics of the basic engine components and structures, and discusses the significant development factors.

Nissan’s new 2.8 liter in-line 6-cylinder turbocharged engine was developed for Che Datsun 280ZX in order to achieve higher performance and improved fuel economy. The Electronic Concentrated Engine Control System (ECCS), controlled by microprocessor, is provided for this 2.8 liter turbocharged engine. ECCS controls fuel injection, ignition timing, EGR rate and idling speed. It solved the problems related to power and fuel economy by optimizing the control parameters. Further, this system contains a barometric pressure compensator and a detonation controller; thus, the performance of this engine is efficient over a wide range of circumstances and fuel octane ratings. During the development of the engine, computer simulation was employed to predict engine performance and select turbocharger size, valve timing and other important factors.

The new Nissan 1.7 liter 4 cylinder diesel engine has been developed to meet the social requirements for energy conservation. The main objective was to improve fuel economy without sacrificing driveability, and this has been achieved by minimizing engine weight, reducing mechanical friction loss and optimizing the combustion system. The CA series gasoline engine, which is known for its light weight, was chosen as the base engine for dieselization. The swirl chamber combustion system used for the LD28 engine was modified to satisfy the requirements for high power, good fuel economy and low noise. Engine noise has been reduced with the aid of several analytical methods such as laser holography. Special attention has been paid to the reduction of diesel knock which is most offensive to the ear. To install this engine in a small FWD vehicle transversely, much effort went into the minimizing of the engine length and width.

An investigation has been done on the relationship between spark ignition characteristics and combustion stability in a gasoline engine. The spark discharge parameters examined were the spark current, energy, and duration. It has been found that lengthening the spark discharge duration is particularly effective in achieving stabilized combustion. A longer spark duration provides a continued supply of electric energy as kinetic energy to the mixture around the spark gap. The analytical results of a constant volume combustion chamber test verify that a longer spark duration promotes flame initiation and makes reliable flame propagation possible. The length of the spark duration is regarded as the period from ignition to the onset of combustion pressure rise. The results of a combustion pressure analysis reveal that the spark duration must be longer than the heat release delay.

In spark-ignition engine pumping loss increases and fuel economy decreases during partial load operation. Methods to reduce this pumping loss by controlling the intake-valve closing timing are currently under study. The authors, also, have confirmed that pumping loss can be reduced by controlling the amount of intake air-fuel mixture through making changes in the in Cake-valve closing timing. However, when pumping loss was reduced by controlling intake-valve closing timing, an improvement in fuel economy equivalent to the reduction in pumping loss was not obtained. In this study, it was found that the major contributing factor to this phenomenon was the deterioration of the combustion, namely, increase in combustion duration and in combustion fluctuation.

In our new fuel injection method, the injector for each cylinder is triggered twice per combustion cycle. The first injection is triggered as early as possible to obtain a good fuel mixture quality. The second injection is triggered as late as possible and as close to the intake valve opening so as to obtain a constant air-fuel ratio even during rapid acceleration. Furthermore, in order to prevent, misfire, timing is calculated based on the fuel amount when the fuel injection occurs. Driveability is improved over a wider range of driving conditions while maintaining good fuel economy and omission control.

Development of a high strength valve spring for automotive engines achieves higher power output and better fuel economy. New material which consists of finely structure and subjected to advanced shot peening, has been developed. Stress analysis of the valve spring moving edge, using the finite element method, has been done for effective application. The merits of this new spring have been confirmed by engine experiments.

Excellent fuel economy and high performance have been urgent in Japanese automobile industries. With increasing engine power, many of the power train components have to withstand higher loads. Differential pinion gear being one of those highly stressed parts, excellent fatigue and shock resistance have been demanded. At first the fundamental study on the fatigue and impact crack behavior of carburized components was studied and the new grade composed of 0.18%C-0.7%Mn-1.0%Cr-0.4%Mo was alloy designed. Furthermore, Si and P is reduced less than 0.15 and 0.015%, respectively aiming at the reduction of intergranular oxidation and improved case toughness. The differential gear assembly test has proved that the new grade shows three times as high impact strength as that of conventional steel, SCM418, and almost the same as that of SNCM420 containing 1.8%Ni.

This paper describes the Nissan R01A model automatic transmission, focusing in particular on the basic design concept, control system and the various control techniques it incorporates. This 4-speed transmission, installed in Nissan's rear-wheel-drive vehicles, was designed from the ground up and significant construction and control mechanism improvements were made over the former conventional model. With a compact gear arrangement consisting of two sets of planetary gears, this transmission features a new electro-hydraulic control system which not only provides optimum shifting and lock-up points, but also modulates the hydraulic pressure electronically to achieve superior shift quality. Control over the transmission is integrated with engine control to deliver improved driveability and better fuel economy. Different transmission variations have been developed to create a versatile lineup for rear-wheel-drive vehicles.

A simulation system has been developed for making comprehensive predictions and assessments of the various and interrelated indices of vehicle performance. This system draws upon a data base containing information on the characteristics of the different units making up a vehicle. The system includes fuel economy and emissions calculation programs incorporating a large number of evaluation items. It also features an acceleration calculation program by which the transient characteristics of a turbocharger can be studied and a vehicle exterior noise program that makes accurate predictions of the pass-by noise level during acceleration. Equipped with a large number of calculation functions the system is an effective tool for improving total vehicle performance.