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An analytical approach to developing motorcycle suspensions is presented. Typical uncontrolled and subjective evaluations that place limits on suspension development are curtailed through the use of a laboratory-based road simulation technique, which evaluates vehicle ride quality. Ride comfort is calculated using a specifically tailored NASA model after primary and secondary frequency regimes have been established for this type of motorcycle. Correlation between road and laboratory simulation is measured and compared to the road data variance. A designed experiment evaluates changes in ride quality as a function of suspension and tire pressure adjustments. Various suspension settings are repeated on the simulator and corresponding ride numbers are calculated for both environments. An analysis is performed to correlate ride quality improvements on the simulator with ride quality improvements in the field.

When the detonation caused by pre-ignition and post-ignition, it is generally known that strong vibrations from the combustion chamber develop from impact of that combustion pressure. This will affect the engine. Methods to accurately measure the strength of this detonation and its usage are being considered and used from various viewpoints. We measure this detonation quantitatively by the detonation counter. This is done in order to bring out optimum performance of the engine, specifically the spots, carburetor settings, and ignition timing. Where adjustments must be made and it is useful as a tool for judging, conducting, and setting adjustment directions and volume quickly and accurately. Furthermore, simplification of this system has the enable it to be sold on the market. As a result of this, it now has spread to and is being used for racing base.

There are several anomalous combustion phenomena that cannot be explained by current theories. One of them is the stoichiometric mixture of hydrogen and oxygen, known as Brown's gas. Dr. Randell Mills developed “hydrino” theory starting in 1986 that can explain excess heat in the absence of nuclear products in the research of cold fusion. It was applied to explain this anomalous combustion, by replacing potassium ion with atomic oxygen. It was found out that hydrino theory can explain this anomalous combustion phenomenon including abnormal heat generation from combustion of emulsified fuels. It was suggested that this technology can be utilized for the improvement of future internal combustion engines.

The authors have experimentally produced a new type of Rotary Valve (ca11ed R.V.) which has a unique gas sealing mechanism. In this study, first, the mechanical loss in the valve train was measured comparing to that of the poppet valve drive train, and it was found that the mechanical loss of rotary valve train is much lower level. Secondary, three dimensional numerical calculation of the flow field from the intake-port to in-cylinder during the intake stroke was carried out. As a result, it was found that the flow field is very complicated due to the interaction between the moving piston and valve and that the profiles of “valve notch” and intake port affect the flow field and then, the modification of profile with a round edge form of the “notch” enables higher mass flow rate.

Experiments were conducted on a small SI engine with the objective to investigate the relationship between air/fuel-ratio and the ionic current signal measured across the spark plug electrodes. The propane-operated, single-cylinder engine has been equipped with sensors to monitor its operating conditions and a CDI ignition system with a built-in ionic current sensing circuit. More than 50 features of the ionic current signal have been examined in a preliminary analysis. Three features of the cycle-averaged signal (signal peak, signal integral in a crank angle window around the peak position, signal amplitude after a preset delay) were found to correlate reasonably well with air/fuel-ratio for the full range of operating conditions. After an evaluation of cycle-to-cycle variations of these features, simple algorithms for an application of the ionic current - mixture strength relationship are introduced.

With emergence of fuel cells which have much better thermal efficiency than internal combustion engines (later abbreviated as ICE), ICE has to improve its thermal efficiency to the level of 50%. One of the ways to improve the thermal efficiency of ICE is to utilize ultra-lean combustion and several technical papers have been published. But it seems the thermal efficiency has not been improved as the theory predicts. The test data of these technical papers were re-examined and it was concluded that the thermal dissociation of burned gas and NOx formation is the key factor of a discrepancy between the theory and the actual test data. In order to prevent an occurrence of thermal dissociation, emulsified fuels (mixture of carbonaceous fuels with water) was proposed.

The purpose of this study is to reveal the flame propagation characteristics. Planar OH* image and local radical emission were measured simultaneously. Planar OH* images were used to analyze the flame propagation characteristics by high-speed camera. These images were then used to evaluate the speed of distribution and the direction of flame propagation. By comparing local point radical emission and planar OH*, the flame propagation characteristics was measured and evaluate that. And the time history of the radical intensity and planar OH* distribution were compared. The relation ship between flame propagation speed and initial heat generation was discussed. The variation of flame propagation speed and the difference of propagation speed in both port sides were confirmed.

The investigation regarding the performance of newly developed plasma jet igniter is explored by using vessel. In plasma jet ignition, combustion enhancement effects occur toward the plasma jet issuing direction. Therefore, when the igniter is attached at the center of cylindrically shaped combustion chamber, plasma jet should issue toward the round combustion chamber wall. The plasma jet igniter that had a concentric circular orifice has been developed. The maximum combustion pressure increases and the burning period decreases with increasing the cavity volume. This feature is similar to that of the ordinary plasma jet igniter. However, the combustion enhancement effect is almost independent of the orifice area.

The application of computational methods for the development of a tuned exhaust system for a small two stroke scooter engine has here been evaluated. A single dimension fluid dynamic code has been employed, in order to simulate engine performances at full load with a prototype exhaust system, and data predicted from computer simulation have been compared with experimental results, obtained using a test rig and a data acquisition system specifically designed for small two-stroke engines. In this way the accuracy of the computer model has been assessed not only as far as gross engine performance parameters are concerned, but also concerning the prediction of pressure values in several locations inside the engine and the exhaust system. Finally, computer simulation techniques have been applied to the development of the prototype exhaust system, and have been proved to be powerful and effective techniques to identify the modifications required to obtain the engine performance targets.

Though most street-use motorcycles are now equipped with 4-stroke engines, off-road motorcycles, especially moto-cross racers, still mainly use 2-stroke engines because of their high power and light weight. 2-stroke engines for moto-cross racers require the engine characteristics of high power and excellent throttle response on a wide range of engine speeds. These characteristics immediately require an effective exhaust device to improve output performance at the middle-speed range while maintaining high power at the high-speed range. The latest 2-stroke engines maintain such performance by using an exhaust device, and also by the application of extensively improved basic elements such as the scavenging passage arrangement, exhaust timing and passage shape, etc. This paper briefly summarizes continuous efforts for the improvement of our exhaust-system device from its beginning until the present.

Measurement using a three-dimensional anemometric-tester was made for the gas flow inside the cylinder of a two-stroke engine while the shape of the transfer port was modified. The relationship between port shape and engine performance was investigated for various factors that characterize the flow in cylinder. In this paper, we focused mainly on two engine running conditions: the maximum output at 11750 rpm and the output at 10000 rpm. As a result, we found that the maximum output is most related to the tangential inclination angles of the main transfer port, and the inner vent radius of the main transfer duct.

To survive the severe regulations for both the exhaust gas emissions and fuel economy, research on small two-stroke gasoline engines from both the experimental and theoretical viewpoints is quite necessary. In the present study, firstly, performance tests of a direct injection small two-stroke gasoline model engine were carried out. Based on these experimental results, three-dimensional flow calculations from scavenging pipe to exhaust pipe during the gas-exchange and piston compression processes were made with the same experimental conditions. As a result, the gas exchange process was investigated and some problems were clarified. Secondly, parametric calculations with changing just exhaust port timings were performed to solve the problems found in the above calculations.

The performance of two-stroke spark-ignition engines is greatly influenced by the scavenging process The variation of the crankcase clearance volume has here been investigated as a method for engine-load reduction. This method allows the reduction of the load without throttling or only by partial throttling with a theoretical increase of the engine efficiency. A comparison of two methods (air throttling and crankcase clearance volume variation) has therefore been carried out. The reduction of pumping work, due to the use of the variable crankcase clearance volume, has not always caused a consequent reduction of the specific fuel consumption. This is mainly due to deterioration of the scavenging process and to the occurrence of pre-ignition which occur above all at light loads.

Two-valve pent-roof type combustion chamber was employed for four stroke cycle small utility engine. The preliminary performance test showed the higher output was obtained by pent-roof type combustion chamber than the conventional bathtub type combustion chamber. CFD analysis and PIV flow visualization proved that the tumble flow is dominant in pent-roof type combustion chamber. From the investigation of the relationship between the tumble ratio and the engine performance by combustion analysis and cycle simulation, it was found out that the tumble ratio from 0.8 to 1.6 is optimal for engine output. By applying the pent-roof type combustion chamber, the developed engines achieved 7-12% increase in output, 8-10% reduction in BSFC. As for the emission, the developed engines can satisfy the CARB regulations.

Reduction of flow resistance in an intake system is essential for increasing the output of a four-stroke engine. Evaluation method regardless engine displacement or number of valves or cylinder must be required in intake system design. This study proposes intake loss coefficient as total evaluation method from flow in an intake port to charging flow into a cylinder. A three-dimensional, general-purpose Computational Fluid Dynamics (CFD) code was used to calculate an intake loss coefficient. A correlation was confirmed between an intake loss coefficient and the engine power output. Intake loss coefficients and the CFD technique may be used for efficient optimization of the shape of an intake system.

The article presents the possibilities of improvements the crankcase delivery ratio in small two-stroke engines by modification of the inlet system by means of an additional side volume connected with the inlet pipe. The results of calculations from numerical simulation of gas physical parameters, taking into account thermodynamic phenomena in the inlet system and crankcase, are closed to those obtained during experiments. Influence of different geometrical parameters of the inlet system on the crankcase delivery ratio is considered. The application of such system increases engine delivery ratio and improves air-fuel ratio over the whole range of engine speed, especially with part-throttle openings and higher engine rotational speed. Simulation and experimental variations of pressure and delivery ratio for various systems have been presented. Good correlation between theory and experiment makes possible a selection of this system at the early stage of design.

A Kohler 725cc air-cooled engine originally designed to operate on gasoline has been modified to run on either gasoline or propane (LPG and still meet current small engine emissions standards. The fuel system being discussed allows the end user, by means of a switch to operate the engine on either propane or gasoline. The paper will discuss a pre-emission dual fuel system and the changes required to meet emission standards and improve performance.

Recently, utilization of CFD (Computational Fluid Dynamics) at the initial stage of motorcycle development is increasing the importance and is becoming indispensable to environment matters. This paper describes a CFD system, which was developed based on PCC (Partial Cells in Cartesian coordinate) method CFD code. The code does not require the mesh generation at each computation. The merit of this system is a full automation after the solid modeling by a 3D-CAD system, such as geometry data transferring, starting of processes, and mailing the results. Moreover, an example of a combination between CFD and DOE (the design of experiment) will be explained. It is an application of an exhaust muffler design of motorcycles. In the past, the decision concerning to the power output during an exhaust muffler design could be done by only a few skilled engineers, but the decision became possible to designers who use this system.

The development of the lightweight and compact EU1000i generator with a maximum output of 1kVA is presented. The technology applied to achieve the required levels of exhaust emission, fuel consumption and noise, and to provide a stable electrical power supply with low waveform distortion is described. The technology comprises of four elements: a high-speed, multi-pole, external rotor type alternator, a microcomputer-controlled sine wave inverter, a compact high-speed 4-stroke engine with electronic speed governing, and a lightweight frame with a two-level noise-damping system. Combination of these four elements of technology has achieved 50% less weight, 25-30% lower fuel consumption, and 7-9dB(A) less noise than the previous model. The emission levels of CO and of NOx + HC are also 30% and 65% lower than the 2000 CARB regulations.

An original multi-body dynamics simulation program for reciprocating engine system with elastically deformable piston skirt was developed in order to understand and examine the secondary motion of piston. This program uses specialized equations of motion using only the rotational degree of freedom of each components taking the valiation of rotating speed of crank into account. In order to validate the practical use of this program, the calculations were compared with the measurements on the piston motion of a two-stroke engine for motorcycles and a four-stroke engine for automobiles, and good agreements were obtained between them.