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Technologies for improving the fuel economy of gasoline engines have been vigorously developed in recent years for the purpose of reducing CO2 emissions. Increasing the compression ratio for improving thermal efficiency and downsizing the engine based on fuel-efficient operating conditions are good examples of technologies for enhancing gasoline engine fuel economy. A direct-injection system is adopted for most of these engines. Direct injection can prevent knocking by lowering the in-cylinder temperature through fuel evaporation in the cylinder. Therefore, direct injection is highly compatible with downsized engines that frequently operate under severe supercharging conditions for improving fuel economy as well as with high compression ratio engines for which susceptibility to knocking is a disadvantage.

The thermal environment in the automotive engine compartment is expected to become increasingly severe in the years ahead owing to the installation of a large-size manifold catalyst to reduce exhaust emissions, among other factors. This will make it even more important to analyze the engine compartment layout in terms of heat flow considerations at the design conceptualization stage of a new vehicle. In this research, a flow analysis program called DRAG4D was applied to find the flow velocity distribution and ambient air temperature distribution in the engine compartment during driving, idling and after the engine was turned off. This original program developed at Nissan takes into account the effects of the energy balance and buoyancy, and provides a practical level of prediction accuracy. The time required to create an analytical model and perform the computations has been shortened by using an automatic grid generation function, based on a solid model, and experimental equations.

This paper proposes a new voice and data wireless communication method for telematics services. Data-voice (DV) modems have conventionally been used for simultaneous transmission of voice and data. With this method, however, one line is split between the data part and voice part. Lost data are retransmitted, but the voice signal is not resent because voice communication requires a real-time characteristic. The new voice and data wireless communication method proposed here switches voice to a voice line and data to a data line.

The aim of this study is to gain a better understanding of the mechanism of knocking with respect to flame propagation behavior based on 3D simulations conducted with the Universal Coherent Flamelet Model. Flame propagation behavior under the influence of in-cylinder flow was analyzed on the basis of the calculated results and experimental visualizations. Tumble and swirl flows were produced in the cylinder by inserting various baffle plates in the middle of the intake port. A comparison of the measured and calculated flame propagation behavior showed good agreement for various in-cylinder flow conditions. The results indicate that in-cylinder flow conditions vary the flame propagation shape from the initial combustion period and strongly influence the occurrence of knocking.

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.

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.

The possibility of predicting engine bearing durability by elastohydrodynamic lubrication (EHL) calculations was investigated with the aim of being able to improve durability efficiently without conducting numerous confirmation tests. This study focused on the connecting rod big-end bearing of an automotive engine. The mechanisms of wear and fatigue, which determine bearing durability, were estimated by comparing the results of EHL analysis and experimental data. This comparison showed the possibility of predicting the wear amount and the occurrence of fatigue by calculation.

The mechanism causing the micro slip characteristic of a metal CVT belt during torque transmission was analyzed, focusing on the gap distribution between the elements. It was hypothesized that gaps between the elements cause slip to occur between the elements and the pulleys when the belt is squeezed between the two halves of the pulleys, and the slip ratio was calculated theoretically on that assumption. The μ-v (friction coefficient versus sliding velocity) characteristic between the elements and the pulleys was measured and the results were used in calculating the slip ratio. As a result, a simulation procedure was developed for predicting the slip-limit torque of the belt on the basis of calculations. The slip ratio found by simulation and the calculated slip-limit torque showed good quantitative agreement with the experimental data, thereby confirming the validity of the simulation procedure.

This paper describes a newly developed adaptive cruise control (ACC) system using continuously variable transmission (CVT) gear ratio control. This system provides excellent headway distance control performance at a reasonable cost. With this system, headway distance is measured with a laser radar, and the throttle position and CVT gear ratio are controlled under both acceleration and deceleration situations. The new ACC system consists of a target headway distance calculator, a headway distance controller, a vehicle velocity controller and a drive torque controller. Using a drive torque control method that was newly developed based on integrated control of engine torque and the CVT gear ratio, the following benefits are obtained. (1) It provides smoother acceleration and deceleration. (2) It maintains the target vehicle velocity on steep uphill and downhill grades. As a result, sufficient ACC performance can be attained even in 2.0-liter class vehicles.

There has been a growing need in recent years to further improve vehicle fuel efficiency and reduce CO2 emissions. JATCO began mass production of a transmission for rear-wheel-drive (RWD) hybrid vehicle with Nissan in 2010, which was followed by the development of a front-wheel-drive (FWD) hybrid system (JATCO CVT8 HYBRID) for use on a midsize SUV in the U.S. market. While various types of hybrid systems have been proposed, the FWD system adopts a one-motor two-clutch parallel hybrid topology which is also used on the RWD hybrid. This high-efficiency system incorporates a clutch for decoupling the transmission of power between the engine and the motor. The hybrid system was substantially downsized from that used on the RWD vehicle in order to mount it on the FWD vehicle. This paper describes various seal technologies developed for housing the dry multi-plate clutch inside the motor, which was a key packaging technology for achieving the FWD hybrid system.

An electric vehicle (EV) has less powertrain energy loss than an internal combustion engine vehicle (ICE), so its aerodynamic accounts have a larger portion of drag contribution of the total energy loss. This means that EV aerodynamic performance has a larger impact on the all-electric range (AER). Therefore, the target set for the aerodynamics development for a new EV hatchback was to improving AER for the customer’s benefit. To achieve lower aerodynamic drag than the previous model’s good aerodynamic performance, an ideal airflow wake structure was initially defined for the new EV hatchback that has a flat underbody with no exhaust system. Several important parameters were specified and proper numerical values for the ideal airflow were defined for them. As a result, the new EV hatchback achieves a 4% reduction in drag coefficient (CD) from the previous model.

An investigation was made of techniques for reducing the friction of lightweighted direct-acting valve train systems. The techniques examined included improving the cam/follower surface finish and reducing the valve spring load. The characteristics of each approach and the valve train friction reduction obtained with each one were clarified by experimentation and analysis. As a result, the friction reduction techniques analyzed in this work reduce the friction level of a direct-acting valve train by approximately 40% in comparison with the previous valve train. These techniques have been applied for the direct-acting valve train system of new-generation, lightweight, 3-liter V6 Nissan engine.

The transient performance of an engine generally depends on the volume of wall flow and behavior of fuel in the induction system which is composed of the intake manifold and the intake port. An experimental technique has been developed for estimating these phenomena in a gasoline engine, which employs a meter for measuring the air-fuel mixture ratio. Using this technique we analyzed single point and multipoint injection systems, and determined the differences in the volume of fuel associated with wall flow. The effects of the shape and specifications of fuel supply system components on the volume of wall flow and fuel behavior in these systems were also made estublished.

In this study the relationship between the timing for the onset of autoignition and the amount of mixture fraction burned by autoignition and the resulting knock intensity is investigated using a combination of high-speed laser shadowgraphy and thermodynamic calculations. It is made clear that over 40 percent of the entire mixture burns due to autoignition in a crank angle of less than five to eight degrees when an engine is operated under a heavy knocking condition. This burn rate is about ten times higher than that of combustion seen in a normally propagating flame. This abrupt heat release causes an oscillation in cylinder gases, resulting in a knocking sound. The experimental procedure is applied to examine the effect of a squish combustion chamber on suppressing knock. The results indicate that, when autoignition occurs in the squish area, an amount of mixture burned by autoignition is small, resulting in lower knock intensity.

An automatic matching method for engine control parameters is described which can aid efficient development of new engine control systems. In a spark-ignition engine, fuel is fed to a cylinder in proportion to the air mass induced in the cylinder. Air flow meter characteristics and fuel injector characteristics govern fuel control. The control parameters in the electronic controller should be tuned to the physical characteristics of the air flow meter and the fuel injectors during driving. Conventional development of the engine control system requires a lot of experiments for control parameter matching. The new matching method utilizes the deviation of feedback coefficients for stoichiometric combustion. The feedback coefficient reflects errors in control parameters of the air flow meter and fuel injectors. The relationship between the feedback coefficients and control parameters has been derived to provide a way to tune control parameters to their physical characteristics.

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.

A new integrated control system has been developed for controlling an SI engine and a CVT proactively so as to obtain the demanded drive torque most efficiently. Taking into account ease of calibration, a control system configuration has been achieved that determines the CVT ratio from the target drive torque and vehicle speed, based on the steady-state relationship between the demanded drive torque and the vehicle speed, gear ratio, engine torque and fuel economy. An analysis was made of drive torque characteristics while the ratio was changing under transient conditions. The results showed that using engine torque to compensate for the ratio change response lag and inertia torque, which is proportional to the differential of the gear ratio, is effective in improving drive torque responsiveness.

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.

Three-dimensional combustion simulation tools together with the Universal Coherent Flamelet Model (UCFM), a flame propagation model, have been applied to SI lean-burn combustion to study the influence of the equivalence ratio on the amount of unburned hydrocarbons (HCs). Unburned HCs from piston-cylinder crevices were taken into the consideration by using a calculation grid incorporating the actual crevice volume and shape and by applying an autoignition model to post-flame phenomena. The calculation results show the general tendencies for the total amount of unburned HCs and their distribution in the combustion chamber.

Reducing friction in the crankshaft main bearings is an effective means of improving the fuel efficiency of reciprocating internal combustion engines. To realize these improvements, it is necessary to understand the lubricating conditions, in particular the oil film pressure distributions between crankshaft and bearings. In this study, we developed a thin-film pressure sensor and applied it to the measurement of engine main bearing oil film pressure in a 4-cylinder, 2.5 L gasoline engine. This thin-film sensor is applied directly to the bearing surface by sputtering, allowing for measurement of oil film pressure without changing the shape and rigidity of the bearing. Moreover, the sensor material and shape were optimized to minimize influence from strain and temperature on the oil film pressure measurement. Measurements were performed at the No. 2 and 5 main bearings.