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Technical Paper

Technologies for Reducing Cold-Start Emissions of V6 ULEVs

New technologies are needed to reduce cold-start emissions in order to meet the more stringent regulations that will go into effect in Europe (EC2000 or EC2005) and in California (ULEV), especially for larger engines such as 6- and 8-cylinder units. One new technology in this regard is the electrically heated catalyst (EHC). However, the use of EHCs alone is not sufficient to achieve the necessary reduction in emissions. This paper discusses techniques for effectively combining the elements of an EHC system, including the introduction of secondary air into the exhaust, improved control of the air/fuel ratio, and an electric power supply method for EHCs. It is shown that it is more effective to promote exothermic reactions in the exhaust manifold than at the EHC. A suitable method for this purpose is to introduce secondary air into the exhaust near the exhaust valves.
Technical Paper

Development of a High-Performance TiA1 Exhaust Valve

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.
Technical Paper

The Development of a High Speed Steel Based Sintered Material for High Performance Exhaust Valve Seat Inserts

The demands on valve seat insert materials, in terms of providing greater wear-resistance at higher temperatures, enhanced machinability and using non-environmentally hazardous materials at a reasonably low cost have intensified in recent years. Due therefore to these strong demands in the market, research was made into the possibility of producing a new valve seat insert material. As a result a high speed steel based new improved material was developed, which satisfies the necessary required demands and the evaluation trials, using actual gasoline engine endurance tests, were found to be very successful.
Technical Paper

Analysis of Thermal Fatigue Resistance of Engine Exhaust Parts

The thermal fatigue resistance of engine exhaust system parts has conventionally been evaluated in thermal fatigue tests conducted with a restrained specimen. However, the test results have not always been consistent with data obtained in engine endurance tests. Two new evaluation methods have been developed to overcome this problem. One is a method of predicting thermal fatigue life on the basis of nonlinear elastic and plastic thermal analyses performed with a finite element model and the ABAQUS program. The other is a method of evaluating exhaust system parts using an exhaust system simulator. This paper describes the concepts underlying the two methods and their relative advantages.
Technical Paper

A New Nissan 3.0-liter V-6 Twin-cam Twin-turbo Engine with Dual Intake and Exhaust Systems

As a new generation sports car engine to lead the field in the 1990s, a 3.0 liter, 60°V, type 6 cylinder, 4 cam, 24 valve engine (VG30DETT) has been developed to achieve the utmost in high performance levels and reliability. it has been mounted on the new model 300ZX and announced in the North America and Japanese markets. The VG30DETT engine is based on the previous VG30DE engine (the engine mounted on the former model 300ZX designed for the market in Japan). The main components, the major driving and the lubrication systems including such parts as the crank shaft,con-rod, cylinder block, piston, exhaust manifold, and oil pan of the VG30DE were thoroughly reviewed and revised. The VG30DETT engine is the result of redesigning the structure of the engine itself and its parts and components to assure durability under, high-level performance requirements.
Technical Paper

Study of the Generation mechanism for Abnormal Exhaust Noise

Based on experimental analysis, the generation mechanism of abnormal exhaust noise which is characterized by an intermittent high frequency aetallic sound, is clarified by bench testing of a FWD vehicle. The noise is caused by large amplitude pressure waves (finite amplitude waves) in the exhaust pipe. They are amplified due to interference between reflected waves and subsequent waves from the engine, and are finally transformed into shock waves in the propagation process along the exhaust pipe, resulting in abnormal exhaust noise. By theoretical analysis of finite amplitude waves, the wave profile in the propagation process and the transition distance to the shock wave can be solved analytically where the assumptions of mass, momentum, and energy conservation are valid, until the moment of shock wave formation. The transition distance is a key parameter in analyzing the growth and existence of shock waves.
Technical Paper

A Portable Fast Response Air-Fuel Ratio Meter Using an Extended Range Oxygen Sensor

The method for measuring air-fuel ratio is generally based on analysis of the exhaust gas components and its calculations. A new instrument has been developed which uses this method, but it attaches an oxygen sensor for exhaust gas analysis to the exhaust pipe and calculates the air-fuel ratio directly from the sensor output using a microprocessor. The response time of this instrument is 100 milliseconds and because it does not require an exhaust gas sampling system its weight is only 2.5 kg. This paper describes the operation theory, construction and characteristics of this instrument, as well as the results of air-fuel ratio of measurements on engines and vehicles using this instrument in a transient state.
Technical Paper

New PM Valve Seat Insert Materials for High Performance Engines

Internal combustion engines experience severe valve train wear and the reduction of valve seat and seat insert wear has been a long-standing issue. In this work, worn valve seats and inserts were examined to obtain a fundamental understanding of the wear mechanisms and the results were applied in developing new valve seat insert materials. The new exhaust valve insert material for gasoline engines is a sintered alloy steel containing Co-base hard particles, with lead infiltrated only for inserts used in unleaded gasoline engines. The new intake valve insert material for gasoline engines is a high-Mo sintered steel, obtained through transient liquid phase sintering and with copper precipitated uniformly. This material can be used for both leaded and unleaded gasoline engines. Valve and valve seat insert wear has long been an issue of concern to engine designers and manufacturers.
Technical Paper

A Unique Dual-Mode Muffler

The techniques harmonizing the contradiction which consists of exhaust noise reduction and engine power increase, have been required for the exhaust muffler. This techniques rapidly improved by means of the clarification due to the acoustic theories and the flow analyses. Recently, according to the passenger car tendency toward high grade and high performance, demands for low noise and high power exhaust systems are increasing year by year. The “Dual Mode Muffler” system (abbreviated, below, DMM) mounted on Nissan Cedric, Grolia and Cima series, installed in 1987, is achieved the consistent of the quietness and the engine power performance. This system is the first control type exhaust system for the 4 wheel car. On previous paper, the analyses of acoustic characteristics on DMM were mainly shown. The analyses of exhaust pressure characteristics are also an important theory along with the acoustic in the development of the exhaust system.
Technical Paper

Aerodynamics Development for a New EV Hatchback Considering Crosswind Sensitivity

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.
Technical Paper

Small Engine - Concept Emission Vehicles

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.
Technical Paper

Economical Matching of the Thermal Reactor to Small Engine-Low Emission Concept Vehicles

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.
Technical Paper

Radiation Noise Due to Longitudinal Vibration of the Exhaust Pipe

The front exhaust pipe and the heat-shield plate of the catalytic converter are excited by the engine vibration. Noise radiation occurs on their surface. Concerning vehicle exterior noise, noise radiated from the exhaust system is often one of major sources as well as engine and exhaust noise. This paper describes the longitudinal vibration model-as a beam-is applied to the high frequency vibration that causes the noise radiated from the exhaust system. It describes also some methods of reducing such noise radiation by isolating the vibration from the front exhaust pipe. These methods are: adding mass to the front pipe, changing the material of the front pipe to a smaller Young's modulus one, installing flexible pipe composed by two sections, and so on.
Technical Paper

Deterioration of Heat Resistant Alloys for Automobile Emission Control Equipment

Various heat resistant alloys are being introduced for use in automobile emission equipment, such as thermal reactors and catalytic converters. For the past several years Japan has been developing alloys which emphasize oxidation resistance. Therefore, oxidation phenomena have been thoroughly researched and clarified. On the other hand, embrittlement, which is a marked deterioration similar to oxide deterioration, has not been studied sufficiently. The major subjects of investigation were the two forms of embrittlement in austenitic heat resistant alloys, caused by the precipitation of σ phase and the absorption of Nitrogen. Useful information was obtained from these results.
Technical Paper

Exhaust Noise Abatement with Porous Sintered Metal Silencer

The exhaust system is often one of the main sources of vehicle noise. A new type of exhaust silencer made of porous sintered aluminum and installed at the end of the exhaust tube considerably reduces this noise, with no rise in back pressure. The mechanism of noise abatement is analyzed utilizing fluid dynamic analysis techniques. It is concluded that noise reduction results mainly from the fluid dynamic effects arising from the gas permeability of the material. Among these effects are the boundary layer control effect of the inner flow, flattening of the velocity profile, heat dispersion effect, decrease in turbulence of flow, smoothing of exhaust pulsation, contraction of the mixing region, and the resulting large decrease in the volume of the noise source. In regard to acoustical effect, the sintered metal can be thought of as Helmholtz resonators. The change in the end condition as an acoustic tube also reduces the peak level of acoustic resonance.
Technical Paper

Impact Study of High Biodiesel Blends on Exhaust Emissions to Advanced Aftertreatment Systems

In Biodiesel Fuel Research Working Group(WG) of Japan Auto-Oil Program(JATOP), some impacts of high biodiesel blends have been investigated from the viewpoints of fuel properties, stability, emissions, exhaust aftertreatment systems, cold driveability, mixing in engine oils, durability/reliability and so on. In the impact on exhaust emissions, the impact of high biodiesel blends into diesel fuel on diesel emissions was evaluated. The wide variety of biodiesel blendstock, which included not only some kinds of fatty acid methyl esters(FAME) but also hydrofined biodiesel(HBD) and Fischer-Tropsch diesel fuel(FTD), were selected to evaluate. The main blend level evaluated was 5, 10 and 20% and the higher blend level over 20% was also evaluated in some tests. The main advanced technologies for exhaust aftertreatment systems were diesel particulate filter(DPF), Urea selective catalytic reduction (Urea-SCR) and the combination of DPF and NOx storage reduction catalyst(NSR).
Technical Paper

Development of Innovative Variable Valve Event and Lift (VVEL) System

Nissan Motor Company has developed a compact and simple new variable valve actuation system called VVEL (Variable Valve Event and Lift) that can vary intake valve lift and valve event angle in a wide range, and adopted it on a newly developed 3.7L, V6 engine. This system combined with a variable valve timing (VTC) mechanism (or a cam phaser) has substantially enhanced engine performance attributes, namely, fuel economy, exhaust emissions, and engine output, because the system has the ability to freely control all of intake valve lift, event duration angle and phasing between intake and exhaust valves. This paper describes an outline of the VVEL system, the principle of system operation, and effects on engine performance attributes by this technology.
Technical Paper

Fuel Enrichment Control System by Catalyst Temperature Estimation to Enable Frequent Stoichiometric Operation at High Engine Speed/Load Condition

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.
Technical Paper

Development of New 1.6Liter Four Cylinder Turbocharged Direct Injection Gasoline Engine with Intake and Exhaust Valve Timing Control System

This paper describes a new 1.6-liter four-cylinder gasoline turbocharged engine with a direct injection gasoline (DIG) system and a twin continuously variable valve timing control (CVTC) system. Demands for higher environmental performance make it necessary to improve engine efficiency further. At the same time, improvement of power performance is important to enhance the appeal of vehicles and make them attractive to consumers. In order to meet these requirements, a 1.6-liter direct injection gasoline turbocharged engine has been developed. By using many friction reduction technologys, this engine achieves the high power performance of a 2.5-liter NA(Naturally Aspirated) gasoline engine and low fuel consumption comparable to that of a smaller displacement engine. In addition, this engine achieves low exhaust emission performance to comply with the US LEV2-ULEV and EU Euro5 emission requirements.
Technical Paper

Impact Study of High Biodiesel Blends on Performance of Exhaust Aftertreatment Systems

Biodiesel Fuel (BDF) Research Work Group works on identifying technological issues on the use of high biodiesel blends (over 5 mass%) in conventional diesel vehicles under the Japan Auto-Oil Program started in 2007. The Work Group conducts an analytical study on the issues to develop measures to be taken by fuel products and vehicle manufacturers, and to produce new technological findings that could contribute to the study of its introduction in Japan, including establishment of a national fuel quality standard covering high biodiesel blends. For evaluation of the impacts of high biodiesel blends on performance of diesel particulate filter system, a wide variety of biodiesel blendstocks were prepared, ranging from some kinds of fatty acid methyl esters (FAME) to another type of BDF such as hydrotreated biodiesel (HBD). Evaluation was mainly conducted on blend levels of 20% and 50%, but also conducted on 10% blends and neat FAME in some tests.