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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.

A periodic impulsive sound at idle is occasionally described as ‘disagreeable’ in two-stroke engines. The relation between combustion conditions, piston vibrations, and the disagreeable sound is analyzed to clarify the phenomena. Some means to alleviate disagreeable sound are then proposed through stabilized combustion, high rigidity sound transfer systems, and refined skirt profiles. Experimental results are shown for the effects on main three factors evaluating disagreeable sound-loudness, impulsiveness, and frequency characteristics. In addition, piston behavior is measured, and the relation between piston motion and disagreeable sound is discussed in this paper.

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.

A centralized control system utilizing optical communication has been developed. Except for the ignition system, almost all electrical functions are under the centralized control. As a method of simplifying wire harness, the time division multiplex communication system using optical communication is adopted. As a result, this new system has made it possible to reduce the number of wires in wire harness from 174 to 123, that of connectors from 60 to 50, and the weight of the wire harness from 1,600 g to 1,350 g. In addition, this system has allowed to reduce the control units (relays) from 11 to 2 (excluding the ignition system).

This paper reports a methodology to estimate combustion pattern and emission by predictive simple simulation with good accuracy on various conditions of PFI engine. 3D-CFD cord VECTIS has been applied for this simulation, its settings and methods are as follows. RANS equation with liner k-epsilon model has been used as the turbulence model. Turbulent burning velocity equation contains not only turbulent velocity term but also laminar burning velocity term. For ignition model, we use a predictive model called DPIK. We iterate cycle calculation until wallfilm behavior is stabilized to get the reasonable mixture formation. We have applied this methodology to 125cc engine of motorcycle. As a result, we have obtained heat release curve and pressure curve with good accuracy on various operating conditions such as engine speed, engine load, air fuel ratio, wall temperature, and spray direction. CO and NOx calculated simultaneously have also been acceptable.

MotoGP is the pinnacle of motorcycle racing, with the world's top riders racing 800cc prototype machines at leading venues around the world. The riders compete against each other to win the title and show their superiority. The manufacturers have improved the engines every year to gain high power with low-fuel consumption. The percentage of the duration in fully open throttle is less than 20% of the race, but the partial throttle is used as much as 80%. Moreover, when the rider accelerates the machine, the front tire is easy to be lifted from the ground. In the middle of corner, the rider cannot open the throttle fully because of the tire slip. Therefore, it is the most important factor to appropriately control a throttle in the partial area. The Drive-By-Wire (DBW) system is one of the solutions for the force control. The vehicle simulation in the engine dyno test helped efficiently to evaluate the DBW.

The purpose of this paper is to investigate the effect of the piston shape and weight on the friction losses. The motoring test was conducted on pistons with various shapes, rigidities, and weights at 3000-16000 rpm. The test results suggested that the piston friction loss would be abruptly increased mainly because of the increase in the skirt friction caused by the change of the piston attitude. Then, the piston behavioral simulation was conducted using a two-dimensional rigid model in consideration of the skirt rigidity, which proved the above suggestion. This paper consists of the paper presented at 1990 JSAE Autumn Convention and the results of the investigation we conducted based on the calculation of piston behavioral simulation.

THE MULTI-VALVE FOUR STROKE CYCLE engine design trend is Coward increased engine power and higher fuel efficiency. While a four-valve system is the most common direction, problems occur when the valve area is widened by increasing the cylinder bore for a higher engine output. The layout of four larger valves causes the combustion chamber shape to flatten and the combustion time period to increase. In pursuit of the optimum multi-valve engine we have studied four, five, six and seven-valve per cylinder design. Performance targets and design constraints led us toward the successful five-valve engine technology. This technology develops high engine torque and efficient combustion over a wide range of engine speeds.

By orthogonalizing the primary inertia moment vector produced by an engine with many engine vectors, a new engine mounting method called “the orthogonal engine mount system” was designed. This paper explains its theoretical background. In addition, a motorcycle with a two-cylinder engine incorporating this system was analyzed by means of modal analysis and building block approach techniques to determine the effectiveness of the orthogonal engine mount system.

In the past, the performance of motorcycle engines has improved quite rapidly through intensive competition in racing and in the marketplace. Motorcycle engines have contributed to the technological progress of internal combustion engines (hereafter abbreviated as ICE). Today's environmental concerns require motorcycle engines to improve fuel economy and exhaust emission pollutants. After examination of potential measures to improve the thermal efficiency of small engines, it was concluded that if engineers of motorcycle engines fail to take on new ideas such as those being developed in cold fusion, it is foreseen that motorcycle engines will be replaced with new power plants as was seen on locomotives in the past.

With the hope of efficient and sophisticated motorcycle engine development, an engine test bed that can simulate vehicle running conditions using an ultra-low inertia motor and high response load control system was constructed, and was applied to the development of engines. By combining an exhaust gas analyzer, an exhaust gas constant volume sampler (CVS), and a data processing system, mass emissions could be measured in various test cycles. This system's advantages for data repeatability and test efficiency compared with a chassis test using a vehicle were confirmed. An acceleration test was conducted to assess running performance, and good agreement with actual driving values was confirmed. In addition, by measuring and evaluating engine response to throttle manipulation, it was possible to evaluate driveability on the test bed. These test findings indicate that this test bed can simulate vehicle driving tests with the engine only and will be a useful tool in engine development.

An apparatus that automatically samples lubricating oil and measures the size distribution of particles in the oil has been developed in order to monitor the state of engines and transmissions in operation. It is a widely known fact that when an engine or transmission seizes or experiences unusual wear, comparatively large pieces of wear debris are released. The goal of the use of the apparatus is to detect these particles of wear debris, stop testing before damage occurs, and clarify the causes. Seizure was, therefore, artificially induced in a transmission, and the wear debris in the oil was closely analyzed following the test. The results showed that when the simulated seizure occurred, large, elongated particles of wear debris were produced. Similar wear debris was observed in oil recovered from the market following the seizure of a component, and at present this is believed to be a type of wear debris characteristic of seizure.

In order to reduce friction and predict wear of the sliding part, it is important to determine the oil film thickness of particular area. A sensor or similar device must be attached to the sliding surface to detect the oil film thickness. However, a sensor could not be attached, due to the lack of space on contact surface, and moreover there was no method to secure the sensor on contact surface at that time. A several-micrometer-thin-film sensor was installed on a sliding surface to attempt measurement, but since the sensor was attached on a contact surface, wear occurred immediately and data was unable to be obtained. To accomplish above issue, we developed a protective layer with excellent wear-resistance that successfully extended the measurement time by protecting the thin-film sensor.

1 Piston design approach for automotive engines has been advanced from both experimental and calculation analysis. However, the developments of experimental analysis method that can verify the accuracy of the calculation analysis are required. In this paper, multi-point thin-film pressure sensor for piston pin-boss part (hereinafter pin-boss) was sputtered on piston pin sliding surface and oil-film pressure distribution was measured in axial and circumferential direction using the pin-boss fatigue tester. Two kinds of pistons with different pin-boss shape (tapered shape) were used in the experiment. The peak pressure of piston with large tapered shape was higher about 20%, compared to the piston with the small tapered shape. As a result of oil film pressure distribution in circumferential direction, it has measured that the oil-film pressure at near side relief was higher than that of piston top side.

A laser Doppler velocimeter is used to measure in real time the velocities of pipe flows in a crankcase-scavenged small two-cycle engine with piston and reed valves. Consequently the optical windows in each pipe must be exchanged instantly by using rotary window systems. The flows in both the inlet and exhaust pipes show different patterns in the motored and firing conditions, but the flows in the scavenging pipe are in a similar pattern regardless of the operating conditions.

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.

In order to establish standard method to evaluate cooling loss in combustion chamber of internal combustion engines based on measurement of instantaneous heat flux / wall temperature with higher response and accuracy than previously reported coaxial type thin-film temperature sensor by applying thin film fabrication technology based on PVD method (Physical Vapor Deposition method) which improved to realize higher responsiveness than the conventional sensor was developed by the authors, and it was confirmed that the sensor has sufficient durability in conditions in which the hydrogen jet and flame directly contacts surface of the sensor by thin-film material change. The influence of the improvement on the measurement accuracy was verified by numerical analysis including thermoproperty evaluation. In this report, the configuration of measurement system that can measure minute voltage from the sensor with low noise and high response is reported.

This paper reports visualization of behavior of spray, wall film, and initial flame propagation in an SI engine with port fuel injection system for motorcycle in order to directly investigate their influences on combustion and relations among them. Borescopes were used to visualize the flame propagation in the combustion chamber and wall film in the intake port. Various injection systems and injection parameters were tested: injection direction, timing, and size of droplets to investigate the effect of mixture formation. It is concluded that combustion stability under low load condition is greatly influenced by mixture inhomogeneity in the combustion chamber whose evidence is the luminous emission. It is caused by direct induction of considerable amount of liquid fuel with large size of droplets into combustion chamber or too inhomogeneous mixture in the intake port.

A simple method is frequently used to calculate a reciprocating engine’s bearing load from the measured cylinder pressure. However, it has become apparent that engine downsizing and weight reduction cannot be achieved easily if an engine is designed based on the simple method. Because of this, an actual load on a bearing was measured, and the measured load values were compared with a bearing load distribution calculated from cylinder pressure. As a result, it was found that some of actual loads were about half of the calculated ones at certain crank angles. The connecting rod’s elastic deformation was focused on as a factor behind such differences, and the rod’s deformation due to the engine’s explosion load was studied. As a result, it was found that the rod part of the engine’s connecting rod was bent by 0.2 mm and became doglegged. Additional investigation regarding these findings would allow further engine downsizing.

A construction of the technology concerning fuel consumption improvement is an important problem not only for the four-wheeled vehicle but also for the motorcycle in recent years when petroleum resources are depleted rapidly. Yamaha originally developed a new fuel injection system (YMJET-FI) and applied the system to a single cylinder, water-cooled and small-displacement engine. In this paper, we would introduce the results of improving the fuel economy with keeping high performance. Improvements were noted in three matters, namely, in the lower load range, 1.Strengthening of in-cylinder flow, 2.Atomization of fuel spray, and 3.Reduction of wall film quantity.