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A new 0.9-liter 4-valve-per-cylinder liquid cooled engine was developed for 1984 model motorcycles. This new engine was optimized from the standpoint of performance, durability, and weight efficiency. Semi-Flat slide carburetors, high compression ratio, relatively short stroke and large valves were employed. This engine was upgraded every other year with changes in displacement. Induction system, exhaust system, and valve train. This paper describes, from the viewpoint of the designer, the evolution of the 4-valve liquid-cooled engine from the 1984 to 1988 models. In that evolutionary process we employed: (1) semi-down draft carburetors with smooth air ducts, (2) a computer-aided intake and exhaust port design and manufacturing system. (3) individual rocker arms. (4) a cool air intake system. (5) lightweight pistons. (6) angle -controlled tightening of connecting rod bolts.

In the closed environments such as manned space station, it is necessary to remove contaminant gas to keep a suitable environment. Removal of gaseous contaminants generated from crew, animals, and plants is important function to keep the environment below the allowable level in the Closed Ecology Experiment Facilities (abbreviated as CEEF). CEEF consist of three modules for habitat, animal and plant, the supporting facilities for each module and a plant cultivation facility. CEEF are scheduled to be constructed from 1994 in Aomori Prefecture, northern part of Japan. For designing Trace Contaminant Control Assembly (TCCA) for CEEF, the following six (6) trace contaminants have been selected as major contaminant gas in CEEF; Ammonia (NH3) Methane (CH4) Ethylene (C2H4) Carbon Monoxide (CO) Nitrogen Dioxide (NO2) Sulfur Dioxide (SO2) Ethylene is well-known as an aggressive contaminant to plant growth and maturity.

It is thought that the synthetic gas, including hydrogen and carbon monoxide, has a potential to be an alternative fuel for internal combustion engines, because a heating value of the synthetic gas is higher than one of hydrogen or natural gas. A purpose of this study is to acquire stable auto-ignition and combustion of the synthetic gas which is supposed to be applied into a direct-injection compression ignition engine. In this study, the effects of ambient gas temperatures and oxygen concentrations on auto-ignition characteristics of the synthetic gas with changing percentage of hydrogen (H2) or carbon monoxide (CO) concentrations in the synthetic gas. An electronically-controlled, hydraulically-actuated gas injector was used to control a precise injection timing and period of gaseous fuels, and the experiments were conducted in an optically accessible, constant-volume combustion chamber under simulated quiescent diesel engine conditions.

In this study on the motorcycle engine, we investigated the geometry of the newly developed intake port with an objective of improving the fuel consumption and the torque in practical range. Herein we present the results obtained. We believe that an effective measure for achieving the stated objective is to improve the combustion speed and combustion stability. To realize that, it is necessary to increase the turbulence during combustion and improve the homogeneity of air-fuel mixture. To investigate the feasible shape of the port, the CFD simulation (including fuel spray analysis) was performed and a geometry that improved the turbulent kinetic energy and mixture homogeneity at the time of ignition was selected. For confirming the combustion improvement effect achieved by tumble strengthening, an engine test was conducted with the same amount of intake air as that used in.

The aim of this study was to clarify the feasibility of applying ion current measurement to detect knock and misfire in lean-burn gas engines. The practical applicability was evaluated by conducting a basic test on a small engine and a test on a large engine. The tests were conducted by advancing the ignition timing to cause knocking, and an evaluation was carried out by comparing the knocking intensity detected by ion current signals and by cylinder pressure signals. By increasing the application voltage and including an amplifier circuit, the weak ion current signals were detected, which indicates that it should be possible to use ion current measurement to detect knock and misfire in lean-burn gas engines.

The rocker arm has a function to lead the cam shaft rotation to the valve operation. There are cases when damages are caused due to abnormal wear at the sliding part, causing certain problems. Authors classified the wear phenomenon, and realized a systematic analysis on the possible cause of the damage. As a result, it was revealed that the damage was of two types, and to prevent the hard wear, it is effective to apply shot peening before plating. The prototype rocker arm was test under various lubricating conditions, thus actually confirming that the occurrence of wear was largely reduced.

Electroimpact and Kawasaki Heavy Industries (KHI) have produced a new riveting process for the forming of Briles type rivets in Boeing 777 and 777X fuselage assemblies. The Briles rivet is typically used for fuselage assembly and is unique in that it has a self-sealing head. Unlike conventional headed rivets such as the NAS1079, this fastener does not require aircraft sealant under the head to be fluid tight. This unique fastener makes for a difficult fastening process due to the fact that interference must be maintained between the hole and fastener shank, as well as along the sides of the fastener head. Common issues with the formed fasteners include gapping under the fastener head and along the shank of the fastener. Electroimpact has employed a host of different technologies to combat these issues with Briles fastening. First, Electroimpact’s patented “Air Gap” system allows the machine to confirm that the head of the rivet is fully seated in the countersink prior to forming.

Motorcycle has broad spectrum of developments, such as excellent engine performance, low fuel consumption, emission and noise reduction. As global warming become a serious issue internationally, reduction of fuel consumption is especially of importance. In this study, an evaluation method for the WMTC mode fuel consumption using a one-dimensional engine simulation is investigated. The fuel consumption for the WMTC mode can be predicted in a short time without a complicated vehicle model to simulate transient behavior. The proposed method mostly showed good agreement with measured data for middle-class motorcycle using a chassis dynamometer.

During high engine load, adequate engine cooling is necessary to prevent irregularly highly machine temperatures and spark knock that are issues affecting high power from being achieved. However, excessive cooling during low engine load or cooling locations that do not require cooling relatively exacerbates fuel consumption. Therefore, optimization of the engine cooling system is needed to achieve higher performance of motorcycle engines. First of all, in water-cooled engines, conventional water cooling system adjusts the cooling amount via flow channel switching with a thermostat, which is opened in high water temperature. However, with the bypass channel, water may bypass the radiator but still continues to circulate, thereby leading to loss arising from heat transfer from the cylinders.

1 In the development of motorcycle engines, a strong feeling of power, an element of being fun to ride has continued strong demand. However, demand to meet environmental performance, a conflicting element, has increased dramatically in recent years and a breakthrough technology that achieves both environmental performance and a feeling of power is in demand. Here, the newly developed engine has greatly enhanced feeling of power while clearing stringent environmental restrictions through use of a centrifugal type supercharger. However, there were several problems that had to be resolved with regards to application of a supercharger to a motorcycle engine. In applying a supercharger to a motorcycle, a major problem is the best way to keep the engine size from increasing in size. The engine, which is the heaviest parts on a motorcycle greatly affects motorcycle maneuverability so it must be compact and the mass concentrated.

In order to improve the fuel efficiency and the operating performance of motorcycles, there is a need to reduce their weight. Magnesium, which is the lightest of the various metals currently being used and has a high specific strength, has the potential to satisfy that need. We conducted a study to clarify the weldability and strength characteristics of, and the most suitable surface treatment for, extruded magnesium alloys and rolled magnesium alloys. Based on the stress analysis by the finite element method, we designed a magnesium swing arm and produced the prototype swing arm by pressing hot rolled AZ31 magnesium alloy plates and welding them. The prototype is about 10% lighter and has higher torsional rigidity than a conventional aluminum swing arm.

Fuel-efficient motorcycles are essential for energy conservation and environmental load reduction. To achieve low fuel consumption, reducing the weight of the body parts of the motorcycle is important. This study focuses on reducing the weight of the swingarms, a relatively heavy body part. However, reducing the weight of swingarms is challenging owing to the low flexibility in their shape because swingarms are conventionally made of multiple pipes and casting parts welded together. Therefore, we utilized the integral casting technology and examined a new light weight shape. However, creating a new shape manually is difficult. Thus, we examined a new shape using the shape optimization technology, which has been recently used in additive manufacturing. The shapes fabricated using this technology are generally complex and difficult to manufacture by casting. Therefore, we adjusted optimization condition with casting.

In response to design requirements for lower weight and higher output, the motorcycle engine cylinder block has evolved from a cast cylinder block to an aluminum alloy cylinder block whose bore walls are surface-treated for wear-resistance. Hard-chromium plating, nickel-compound plating, and the like are in wide use as the wear-resistance surface treatment method, but spray technology has recently been attracting attention because of less impact on the environment, superior initial running-in performance and good oil retention. We have been applying a unique spraying method called wire explosion spraying to those models with a special need for wear-resistance surface. In this report we describe our wire explosion spray technology. With the aim of improving the bond strength of the sprayed coat, we studied the effects of the collided particles' form on bond strength in the wire explosion spraying conditions.

The authors developed a gasoline engine that combined direct injection and port fuel injection in order to improve fuel economy for motorcycles. Compared to passenger car engines, motorcycle engines generally have smaller displacement and operate at higher engine speed, so the bore and stroke are generally smaller than those of passenger cars. Therefore, the direct injection spray characteristics optimized for small bore and stroke were selected to reduce fuel adhesion to various parts of the combustion chamber wall. In addition, this engine employed the high tumble intake port that can both strengthen turbulence intensity and suppress the decrease in volumetric efficiency to a lower level. Also, stratification of air-fuel mixture and split injection were employed for reducing catalyst warm-up time and soot. The results showed that excellent fuel economy was achieved without sacrificing engine output performance while meeting emissions regulations.

Environmental and energy independence concerns have stimulated the development of an apparatus for alternative fuel. It estimates the ethanol content in the fuel in order to perform a reliable combustion. One means for measuring the ratio of ethanol present in the fuel tank is to provide a fuel composition sensor. However, such a fuel composition sensor increases the number of parts and causes the cost issues in motorcycles. We used an oxygen sensor disposed to the exhaust pipe to estimate the ethanol content without increasing the parts and costs. The common method of the estimation is the oxygen feed-back in stoichiometric air fuel ratio condition. Unfortunately, two-wheel vehicles are often operated in rich conditions and have less chance of stoichiometric condition. In this study, we used a one-liter four-cylinder motorcycle, and have developed a practical method to estimate the ethanol content even in the not-stoichiometric condition.

Abnormal combustion, which is a cause for engine failure, is explicated to be high speed knocking by multi-cycle analysis of the cylinder pressure data of snowmobile two stroke cycle engines operated at high speed and wide open throttle condition. A mini-computer was used for the analysis of the cylinder pressure data. Calculation of the entire cycle was conducted until an engine actually failed and the relationship between the engine failure and the conditions surrounding the knocking was made clear. Using the rate of pressure change as a quantitative evaluation method for high speed knocking, a combustion chamber shape with less knocking occurrence possibility was selected.

In this study, characteristics of the development and auto-ignition/combustion of hydrogen jets were investigated in a constant-volume vessel. The authors focused on the effects of the jet developing process and thermodynamic states of the ambient gas on auto-ignition delays of hydrogen jets. The results show that the ambient gas temperature and nozzle-hole diameter are significantly effective parameters. By contrast, it is clarified that the ambient gas oxygen concentration has a weak effect on the auto-ignition/combustion of hydrogen jets. Consequently, it is supposed that the mixture formation process is capable of improving the auto-ignition/combustion of hydrogen jets.

In recent years, there has been a need to reduce CO2 emissions from internal combustion engines in order to achieve an energy-saving and low-carbon society. Against this backdrop, the authors have focused attention on Homogeneous Charge Compression Ignition (HCCI) combustion that achieves both high efficiency and clean emissions. With HCCI combustion, a premixed mixture of fuel and air is supplied to the cylinder and autoignited by piston compression to drive the engine. Autoignition makes it possible to operate the engine at a high compression ratio, enabling the HCCI combustion system to attain high efficiency. However, HCCI combustion also has some major unresolved issues. Two principal issues that can be cited are ignition timing control for igniting the mixture at the proper time and assurance of suitable combustion conditions following ignition to prevent incomplete combustion and knocking.