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This study deals with reduced-order modeling of intake air dynamics in single-cylinder four-stroke naturally-aspirated spark-ignited engines without surge tanks. It provides an approximate calculation method for embedded micro computers to estimate intake manifold pressures in real time. The calculation method is also applicable to multi-cylinder engines with individual throttle bodies since the engines can be equated with parallelization of the single-cylinder engines. In this paper, we illustrate the intake air dynamics, describe a method to estimate the intake manifold pressures, and show experimental results of the method.

The improvement of fuel consumption is the most important issue for engine manufactures from the viewpoint of energy and environment conservation. A piston-cylinder system plays an important role for the reduction of an engine friction. For the improvement of the frictional behavior of the piston-cylinder system, it is beneficial to observe and analyze the frictional waveforms during an engine operation. To meet the above-mentioned demand, frictional waveforms were measured with using the renewed floating liner device. In the newly developed floating liner device, an actual cylinder block itself was used as a test specimen. The measured single cylinder was an aluminum monolithic type made of hypereutectic Al-17%Si alloy using a high pressure die casting process. The combined piston was a light weight forged piston and a DLC coated piston ring was used. For the measurement, 110cc air cooled single cylinder engine was used.

Recently, our research has focused on the weave mode. This is a representative vibration mode of motorcycles and is important when considering maneuverability and stability. In a method of analyzing the weave mode, a disturbance is applied to the handle bars of the motorcycle during running and then the response waveform of the roll angle and other items at that time is used to perform estimations. However, when the motorcycle is driven at low speeds, the steering operations of the rider have a large effect on the running data and this makes estimation difficult. Therefore, it was assumed that weave mode data can be estimated from slalom running data since this possesses almost the same vibration frequency as the weave mode in low speed range. In this research, a simulation was used to investigate the relationship between the weave mode and slalom running.

A connecting rod made of titanium alloy is effective for lower fuel consumption and higher power output comparing to a steel one because the titanium connecting rod enables to reduce the weight of both of reciprocating and rotating parts in an entire engine substantially. But up to now, it has been adopted only to expensive and small-lot production models because a material cost is high, a processing is difficult and a wear on a sliding area should be prevented. In order to adopt the titanium connecting rods into a more types of motorcycles, appropriate materials, processing methods and surface treatment were considered. Hot forging process was applied not only to reduce a machining volume but also to enhance a material strength and stiffness. And the fracture-splitting (FS) method for the big-end of the titanium connecting rod was put into a practical use.

Gasoline fueled Homogeneous Charge Compression Ignition (HCCI) combustion with internal exhaust gas re-circulation using Negative Valve Overlap (NOL) was investigated by means of calculation and experiment in order to apply this technology to practical use with sufficient operating range and with acceptable emission and fuel consumption. In this paper we discuss the basic characteristics of NOL-HCCI with emphasis on the influence of intake valve timing on load range, residual gas fraction and induction air flow rate. Emission and fuel consumption under various operation conditions are also discussed. A water-cooled 250cc single cylinder engine with a direct injection system was used for this study. Three sets of valve timing were selected to investigate the effect of intake valve opening duration. Experimental results demonstrated that an engine speed of approximately 2000rpm yields an NMEP (Net Mean Effective Pressure) range from 200kPa to 400kPa.

We focus on the control issue for engine systems from the perspective of chaos theory, which is based on the fact that engine systems have a low-dimensional chaotic dynamics. Two approaches are discussed: controlling chaos and harnessing chaos, respectively. We apply Pyragas' chaos control method to an actual engine system. The experimental results show that the chaotic motion of an engine system may be stabilized to a periodic motion. Alternatively, harnessing chaos for engine systems is addressed, which regards chaos as an essential dynamic mode for the engine.

Regarding S.I. gasoline engine, it is one of the most important matters to eliminate cyclic variation of combustion. Especially with high compression ratio and high boosted engine, the difficulties increase more. This paper describes the analysis of combustion process precisely by using many ion-current probes and CFD with the unique approaches. The number of used ion-current probes is 80 and they are mounted on whole combustion chamber wall especially including moving intake and exhaust valve faces. Thus cyclic variations of flame propagation can be measured precisely under high compression ratio and high boosted conditions in a multi-cylinder engine. In addition, CFD combustion simulation is conducted through full four strokes of continuous nine cycles. Moreover air motion and pressure vibration in intake and exhaust manifolds in whole cycles are considered. These unique approaches have made CFD result correspond to the measurement result of cyclic variations of actual combustion.

In this study, lean combustion concept was investigated to realize better Fuel Economy (FE) on a single cylinder motorcycle engine. A low-pressure direct injection (DI) system was applied to realize lean stratified combustion concept with good combustion stability. In addition, Exhaust Gas Recirculation (EGR) system applicable to small motorcycle engines was used to attain FE improvement and NOx reduction. EGR gas temperature and EGR return position were focused on and effects on FE and NOx were investigated. Computational Fluid Dynamics (CFD) was used to reveal EGR distribution and air motion in both the intake port and the cylinder. As a result, the influence of the stratified charge, EGR temperature and EGR return position on FE and NOx were explained quantitatively. These techniques were effective in reducing NOx and improving FE for a single cylinder motorcycle engine.

Attempts have been made to develop an electronically controlled fuel injection system that is ideal for small motorcycles, cost-efficient, compact, and electric power-saving while maintaining accuracy. For reducing the number of sensors and cost, highly accurate methods have been developed for the measurement of intake air mass, detection of acceleration, distinction of engine stroke, and estimation of atmospheric pressure without using a throttle position sensor, cam timing sensor, and barometric sensor in such a manner as to carry out sampling with the intake manifold pressure of single-cylinder engines synchronizing with the crank angle. For compactness and electric power saving, an injector and in-tank fuel pump module have been developed for small motorcycles.

Reduction in the cycle-to-cycle variation (CCV) of combustion in internal combustion engines is required to reduce fuel consumption, exhaust emissions, and improve drivability. CCV increases at low load operations and lean/dilute burn conditions. Specifically, the factors that cause CCV of combustion are the cyclic variations of in-cylinder flow, in-cylinder distributions of fuel concentration, temperature and residual gas, and ignition energy. However, it is difficult to measure and analyze these factors in a production engine. This study used an optically accessible single-cylinder engine in which combustion and optical measurements were performed for 45 consecutive cycles. CCVs of the combustion and in-cylinder phenomena were investigated for the same cycle. Using this optically accessible engine, the volume inside the combustion chamber, including the pent-roof region can be observed through a quartz cylinder.

The finite element method (FEM) is generally utilized to investigate the chassis strength of a motorcycle. However, it is difficult to determine the load conditions for FEM analysis of a drop test. Therefore, a method of drop test strength prediction at the basic design stage has been developed by combining stress analysis with vehicle dynamics analysis. A mathematical model and computer simulation system have been developed to predict the load conditions obtained by accelerations at several chassis locations. The model is constructed using flexible bodies (e.g., front fork and rear arm) as well as rigid bodies. The flexible front fork model was made by combining beam theory with substructural methods. Also, the model includes a front fork friction model which describes Coulomb's friction in slide bushings. If dynamic analysis is replaced by an equivalent static analysis, the force can be predicted from the acceleration data and the mass distribution.

This paper concerns the development and validation of a three-dimensional mathematical model representing a motorcycle with rider. As part of this development, several motorcycle to barrier tests were performed at the laboratories of the TNO Crash-Safety Research Centre and several measurements were carried out, including measurements to determine the inertia properties of the motorcycle segments. Results of two full scale tests involving a passenger car were then applied to validate the model in a more realistic crash environment. The resulting MADYMO motorcycle model consists of 7 bodies linked to each other by joints and spring-damper type elements. Special attention was given to the mathematical representation of front fork, front wheel and gastank. A 50th %ile Part 572 dummy with pedestrian pelvis and legs represented the rider. For representation in the model an existing dummy database was updated.

A mathematical model to estimate the shape of a brake hose has been developed. A few papers applying Finite Element Methods (FEM) to this problem have been reported. However, the solutions require a large amounts of computational time even if a super computer is used. A brake hose is made of a flexible material such as rubber, and exhibits large scale deformation when it is mounted on a chassis. Element node displacements are chosen as the independent variables for FEM, so the method becomes a successive iteration of hose shape modifications based on displacements of the nodes. The developed model is approached from the standpoint of mechanical dynamics. A brake hose is divided into small beam elements and particles. The particles are driven by element forces and move around in three-dimensional space.

We compared motoring friction loss, output performance at WOT (wide open throttle) and specific fuel consumption of big-end bearings on engines having identical specifications between the case of using plain bearings and rolling bearings to investigate the effect of the lubricating oil supply rate on these parameters in an attempt to improve output through reduction of friction loss for big-end bearings of small, high-output motorcycle engines. Testing was performed using a 125 cc, 4-cycle, single cylinder engine at high engine speeds mainly above 10,000 rpm.

Any improvements of the fuel economy with engines are always required for all petroleum fuel vehicles. The goal of such improvements must lead to reduce fuel consumption of the engines. However it may cause some deterioration with riding feeling that is one of the most important characteristics of the motorcycles. Yamaha has developed the strong hybrid motorcycle "HV-X"(hereafter the motorcycle). The motorcycle consists of a 4-stroke 250 cm₃ a cylinder engine and two 300V AC motors with a planetary gear set. The motorcycle reduces fuel consumption without severe influence onto the drive performance by utilizing the electric power.

The propeller blade hydrofoil section is one of the factors that determines the propeller performance. In the development of the hydrofoil, repeatedly performed experiments using many foil models and the cavitation tunnel involve extended time and high cost. This is why there are expectations for the numerical simulation to realize shorter development time and cost cutback. On the other hand, a technique for reproducing the hydrofoil characteristics taking account of the cavitation effect using CFD (Computational Fluid Dynamics) has hardly been established. There is no example of performance prediction especially for a hydrofoil section of the outboard motor propellers in which the trailing edge is cut off. This paper describes the results of the prediction of hydrodynamic characteristics performed in regard to the two differently shaped outboard motor propeller blade hydrofoil sections taking account of the cavitation effect.

In this study, an improvement of fuel consumption by changing the exhaust timing of a two-stroke engine has been made. The study results revealed that a remarkable improvement of fuel economy is possible by controlling the exhaust timing according to the engine speed. The reason for the better fuel economy was clarified through an analysis of exhaust gases, theoretical cycle calculations, and an analysis of combustion pressure. As an example of actual application, the results of tests made on an engine equipped with Yamaha power Valve System (YPVS), which is a variable exhaust timing mechanism using a tabor-shaped valve, will also be discussed.

Abnormal valve gear vibration is a perennial problem confronting the designer of high-performance 4-stroke engines. It would shorten time and reduce costs if an analytical method could be applied to the prediction of engine valve behavior. This paper describes a method of valve motion simulation for both SOHC and DOHC valve gears through interactive calculation and using computer graphics. The authors tried to set up as simple a simulation model as possible by using modal analysis and modeling techniques. Through setting simulation model parameters and experimental damping factors, a close correlation between calculated and actually measured results was found.

Recently it is becoming more necessary than ever to carry out performance prediction and factor analysis at the initial design by-computer aided engineering (CAE), in order to ensure the high performance, safety and reliability of motorcycles and also to shorten the lead time of product development. Finite element method (FEM) plays a crucial role in this respect. In particular, since the vibration characteristic is one of the most important evaluation items, the demand for accurate vibration prediction at the initial design has become much more intense. In recent years, vibration simulation methods have achieved remarkable progress, and especially the substructural synthesis method (SSM), combined with FEM, is used as an effective tool for the requirements.

To investigate the chassis strength of a motorcycle, the Finite Element Methed (FEM) is generally utilized. However, it is difficult to determine the load conditions for FEM analysis on rough terrain. A mathematical model and computer simulation system have been developed to predict the load conditions which is obtained by accelerations at several chassis locations. The dynamic behavior of a motorcycle is simulated on a bench test device composed of rotating drums fitted with protrusions. The model is constructed using flexible bodies (e.g., front fork and rear arm) in addition to rigid bodies. The flexible front fork model was made by combining beam theory with the substructural method. Also, the analysis includes a tire model which expresses the force characteristics when protrusion is enveloped. The calculated results of this model correspond with actual measurements very closely. The model is necessary and sufficient from the points of view of simplicity and accuracy.