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It is important to understand the influence of housing stiffness on bearing performance, particularly for the connecting rod bearings of automotive engines. It is known that the engine lubricant shows a piezoviscous characteristic whereby its viscosity changes under the influence of pressure. Engine bearings under a heavy load are apt to be influenced in this way. In this study, the effects of connecting rod stiffness and lubricant piezoviscosity on bearing performance were examined by elastohydrodynamic lubrication (EHL) analysis under conditions corresponding to the high-speed operation of an actual engine. The results indicated that under such heavy load conditions housing stiffness greatly affects friction loss because of lubricant piezoviscosity. It was also found that the piezoviscosity of the lubricant has a large effect on bearing performance, as does its viscosity under atmospheric pressure.

With the development of downsized spark ignition (SI) engines, low-speed pre-ignition (LSPI) has been observed more frequently as an abnormal combustion phenomenon, and there is a critical need to solve this issue. It has been acknowledged that LSPI is not directly triggered by autoignition of the fuel, but by some other material with a short ignition delay time. It was previously reported that LSPI can be caused by droplets of lubricant oil intermixed with the fuel. In this work, the ignition behavior of lubricant component containing fuel droplets was experimentally investigated by using a constant volume chamber (CVC) and a rapid compression and expansion machine (RCEM), which enable visualization of the combustion process in the cylinder. Various combinations of fuel compositions for the ambient fuel-air mixture and fractions of base oil/metallic additives/fuel for droplets were tested.

In recent years, the slip lock-up mechanism has been adopted widely, because of its fuel efficiency and its ability to improve NVH. This necessitates that the automatic transmission fluid (ATF) used in automatic transmissions with slip lock-up clutches requires anti-shudder performance characteristics. The test methods used to evaluate the anti-shudder performance of an ATF can be classified roughly into two types. One is specified to measure whether a μ-V slope of the ATF is positive or negative, the other is the evaluation of the shudder occurrence in the practical vehicle. The former are μ-V property tests from MERCON® V, ATF+4®, and JASO M349-98, the latter is the vehicle test from DEXRON®-III. Additionally, in the evaluation of the μ-V property, there are two tests using the modified SAE No.2 friction machine and the modified low velocity friction apparatus (LVFA).

Engine oil with viscosity lower than 0W-16 has been needed for improving fuel efficiency in the Japanese market. However, lower viscosity oil generally has negative aspects with regard to oil consumption and anti-wear performance. The technical challenges are to reduce viscosity while keeping anti-wear performance and volatility level the same as 0W-20 oil. They have been solved in developing a new engine oil by focusing on the molybdenum dithiocarbamate friction modifier and base oil properties. This paper describes the new oil that supports good fuel efficiency while reliably maintaining other necessary performance attributes.

Nissan utilizes ceramics in the turbine rotor of turbochargers to improve acceleration response by reducing the inertia weight of the turbine rotor. Since ceramic material does not yield, a high degree of localized stress will cause it to fail. Therefore, in order to be able to apply this brittle material to a high-speed rotor under high-stress conditions, silicon nitride material has been improved, and a low-stress shape employing the three-dimensional finite element method developed. Furthermore, a new technique for bonding the ceramic rotor to a metal shaft is employed in order to reduce residual stress caused by the difference in thermal expansion coefficients between the ceramic and metal materials. Since the strength of ceramics varies widely, it was necessary to confirm the reliability of the ceramic rotor and evaluate its life of fatigue. This paper, then, describes the design philosophy, bonding method, reliability and durability of the ceramic rotor.

The thinnest wall thickness of automotive catalyst substrates has previously been 30 μm for metal substrates and 50 μm for ceramic substrates. This paper describes a newly developed catalyst substrate that is the world's first to achieve 20-μm-thick cell walls. This catalyst substrate features low thermal capacity and low pressure loss. Generally, a thinner cell wall decreases substrate strength and heat shock resistance. However, the development of a “diffused junction method”, replacing the previous “wax bonding method”, and a small waved foil has overcome these problems. This diffused junction method made it possible to strengthen the contact points between the inner waved foil and the rolled foil compared with previous substrates. It was also found that heat shock resistance at high temperature can be much improved by applying a slight wave to the foil instead of using a plane foil.

Nissan has added ball bearings to its “High-flow Ceramic Turbocharger”(1) (introduced in 1987) to improve acceleration response by reducing friction loss. The following programs were carried out in applying ball bearings to the turbocharger: Optimum bearing size and material were selected to assure long life; lubrication techniques were employed to achieve compatibility between acceleration response and durability; a thrust support system was designed to assure that the ball bearings endure thrust load which varies in direction and magnitude during engine operation; and the squeeze film damper was optimized to keep the turbocharger silent. These innovations have resulted in a practical ball-bearing turbocharger, which has been installed in Nissan's most recent Skyline model(released in May 1989). This is the first time a ball-bearing turbocharger has been applied to a passenger car.

This paper presents a new refrigeration lubricant for use with the HFC-134a retrofit refrigerant in automotive air-conditioning systems originally designed to use the CFC-12 refrigerant, one of the regulated CFCs scheduled to be phased out. This new retrofit lubricant provides high lubricity and excellent performance characteristics as a result of adopting a newly developed PAG base oil with a block polymer structure and a new antiwear additive formulation. In retrofit systems, it assures sufficient durability for wobble-plate-type variable displacement compressors, which experience severe lubrication conditions.

The higher output levels attained by recent automotive engines have been accompanied with an increase in the amount of heat generated by the engine. This higher heat release level, together with the styling trend toward a lower hood line, requires a method for accurately predicting heat release to the engine coolant. In this research, the heat flow path in the engine was separated into several components and equations were formulated for estimating the amount of heat released by each component. The whole heat release to the engine coolant was obtained by totaling the heat release of each component.

Being able to plan each powertrain performance parameter with improved accuracy is an important factor for shortening the development period. In this regard, advance temperature predictions are particularly important because of the strong correlation between the thermal design and the vehicle layout, engine proper and other related parts. At present, it is still difficult to make thermal performance predictions for the engine oil temperature. There are many examples of studies in which the oil temperature was predicted in a one-dimensional circuit. In those studies, either experimental data were used for the heat release from engine components to the oil or calculations were made with a model that was converted empirically from three-dimensions to one-dimension. Because the mechanisms of oil temperature changes inside the engine are not well understood in detail, it is not possible to examine how modifications of the engine structure might affect the oil temperature.

The purpose of this work was to gain a fundamental understanding of which fuel property parameters are responsible for particulate emission characteristics, associated with key intermediate behavior in the engine cylinder such as the fuel film and insufficient mixing. Accordingly, engine tests were carried out using various fuels having different volatility and chemical compositions under different coolant temperature conditions. In addition, a fundamental spray and film visualization analysis was also conducted using a constant volume vessel, assuming the engine test conditions. As for the physical effects, the test results showed that a low volatility fuel displayed high particulate number (PN) emissions when the injection timing was advanced. The fundamental test clearly showed that the amount of fuel film on the impingement plate increased under such operating conditions with a low volatility fuel.

Front-end airflow predictions are generally carried out at the styling stage in the development process for vehicle cooling systems. These predictions have taken on increasing importance in recent years in studying the heat radiation capacities of the radiator. This paper presents a method for simulating front-end airflow rates. Two- and three-dimensional front-end airflow simulations are iirst analyzed experimentally. A technique for predicting a three-dimensional airflow from a numerical analysis of a two-dimensional airflow is then examined, and a comparison is made with actual vehicle data. A sample application of this simulation method is presented and a comparison is made with experimental data. Good quantitative agreement is seen between the calculated and experimental results. This paper also discusses the present status of three-dimensional analysis which is expected to become a major trend in the future.

A gasoline particulate filter (GPF) is installed in a passenger vehicle for new exhaust regulation. However, ash in gasoline engine oil has a risk of clogging as well as performance decrease in the GPF. Therefore, new gasoline engine oil whose ash contents decrease to 0.8 mass% was developed in order to avoid the GPF clogging. In addition to this, our developed oil improves fuel efficiency (+0.2% from our SN 0W-16 fuel eco type oil) as well as anti-wear performance for gasoline engine, which resulted in meeting API SP/ILSAC GF-6 0W-16 official certification.

The new lubricant was newly developed for differential gear unit to contribute to all friction factors/conditions (Boundary, Hydrodynamic & those Mixed Lubrication) even if the differential gear is operating under very severe conditions such as high-gear-contact pressure and highly sliding speed. The main concept of development was selecting and formulating the optimized additives for severe lubrication conditions in order to achieve the best balance between thinner-film thickness and extreme pressure performance. In conclusion, by the application of both synthetic base oil instead of mineral one and activation technology of MoDTC in spite of ZnDTP free formulation, it is finally realized to reduce the torque of final drive unit by 40% and it can be estimated the 0.5% of CO2 reduction in actual vehicles.

Mechanism of suddenly occurring behavior of low speed pre-ignition (LSPI) in boosted spark ignition (SI) engines was analyzed with various experimental methodologies. Endoscope-visualized 1st cycle of LSPI showed droplet-like luminous flame kernels as the origin of flame propagation before spark ignition. With the oil lubricated visualization engine, droplets flying were observed only after enough accumulation of fuel at piston crevice. Also, it was confirmed that subsequent cycles of LSPI occur only after enough operation time. These results indicated that local accumulation of liner adhered fuel and saturation of oil dilution can be a contributing factor to the sudden occurrence of LSPI.

During this decade, the constant increase and globalization of passenger car sales has led countries to adopt a common language for the treatment of CO2 and other pollutant emissions. In this regard, the WLTC - World-wide harmonized Light duty Test Cycle - stands as the new global reference cycle for fuel consumption, CO2 and pollutant emissions across the globe. Regulations keep a constant pressure on CO2 emission reduction leading vehicle manufacturers and component suppliers to modify hardware to ensure compliance. Within this balance, lubricants remain worthwhile contributors to lowering CO2 emission and fuel consumption. Yet with WTLC, new additional lubricant designs are likely to be required to ensure optimized friction due to its new cycle operating conditions, associated powertrain hardware and worldwide product use.

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.

A technique has been developed which permits the determination of engine oil consumption on an instantaneous basis. The procedure uses the sulfur in the oil as a tracer. The concentration of sulfur compounds in the exhaust gas is determined using a Flame Photometric Detector (FPD). Special modifications of the FPD reduce the interference of other gases and improve the accuracy of the instrument. Although the unit is operationally simple, its abilities to measure continuously and respond quickly allow it to surpass conventional methods for measurement of oil consumption.

A flow analysis method with quick turnaround time has been studied for application to flows in the engine compartment of vehicles. In this research, a rapid modeling method based on the Cartesian mesh system was developed to obtain flow field information quickly. With this modeling method, the original shape is approximated by many small cubic cells, allowing automatic mesh generation in significantly less time. Moreover, a hierarchical mesh system that reduces the total number of meshes has been introduced. This multi-level mesh system is also highly capable of representing shapes in detail. Another important issue in flow calculations in the engine bay is the treatment of the boundary conditions such as the radiator and cooling fan. With the proposed method, the fluid dynamics characteristics of such components are measured, and characteristics such as the pressure loss/gain and the rotational vector of the fan are reflected in the flow field as empirical models.

Ceramic honeycombs have been used as automotive catalyst supports in US, Japan, Europe and other highly urbanized countries. Now, engine output is a great concern for automanufacturers, and reduction of the wall thickness of honeycomb substrates became indespensable for maintenance of gas flow restriction to a certain low level. To reduce wall thickness, material should be strong to maintain canning strength of substrates. Mechanical strength was improved with high density cordierite. However, isostatic strength of whole substrates was still insufficient with reduced thin walls for canning in spite of the material's high mecanical strength. Discussion is carried out on further possibility of improving canning performance of thin wall substrates as well as flow restriction, and warm up characteristics.