Search Results

Significant advancements have been made in recent years in the development of combustion system for spark-ignition direct-injection engine (SIDI) engine, which have resulted in fuel economy saving, low exhaust emission and a significant power advantage under homogeneous fuel operation, compared to equivalent PFI (Port Fuel Injection) engines. Key challenge for small-displacement SIDI engine, which has short path lengths between the injector and piston and is therefore prone to increase wall wetting, is minimizing or eliminating the amount of wall wetting to reduce smoke emission. A side-injection system also requires sufficient spray penetration to fully transport fuel to the centrally mounted spark plug at the desired injection timing event.

The automobile industry presently focuses on improving fuel economy and reducing the weight of vehicles. One part of these efforts is to develop high-performance engines for improved combustion efficiency and lower emissions. Against this background, many high-performance motorcycle engines use forged pistons made of extruded or continuously cast aluminum alloy for high reliability and material properties. The cost of forged pistons is higher than that of gravity die cast pistons. To replace these expensive forged pistons, a low-cost, high-performance piston with increased endurance and thermal resistance has been developed using a newly developed aluminum alloy and a high-quality die casting technology using an oxygen supply system and additional pressure.

The present turbo-charged direct injection 660cm3 engine achieves low engine-out emissions and low fuel consumption with high engine output because of synergies of direct injection combined with turbo-charging. The fuel mixture in the combustion chamber is slightly stratified and is slightly richer than stoichiometric in the vicinity of the spark plug at the time of ignition, thereby yielding stable combustion. This reduces the unburned HC at cold start operation and makes is possible to retard spark timing at cold start operation, which activates the catalyst quicker and reduces exhaust emissions. Also, the stable combustion allows introduction of higher EGR(Exhaust Gas Recirculation) rates, which reduces NOx emission and improves fuel economy resulting from low pumping loss. Due to charge cooling, the compression ratio can be increased, which has inherent fuel economy advantage as well.

Superior fuel economy was achieved for a small-displacement spark-ignition direct-injection (SIDI) engine by optimizing the stratified combustion operation. The optimization was performed using computational analyses and subsequently testing the most promising configurations experimentally. The fuel economy savings are achieved by the use of a multihole injector with novel spray shape, which allows ultra-lean stratification for a wide range of part-load operating conditions without compromising smoke and hydrocarbon emissions. In this regard, a key challenge for wall-controlled SIDI engines is the minimization of wall wetting to prevent smoke, which may require advanced injection timings, while at the same time minimizing hydrocarbon emissions, which may require retarding injection and thereby preventing over-mixing of the fuel vapor.

A new 660cc turbo-charged Spark-Ignition Direct-Injection (SIDI) engine was developed. The mini-car equipped with this engine is the first mini-car with a turbocharged SIDI engine to receive the Japanese Ultra-Low-Emission-Vehicle (ULEV) certification. The vehicle achieved a 5.7% fuel economy improvement on the Japanese 10-15 mode compared to the mini-car equipped with the baseline port fuel injection (PFI) engine. The baseline engine is currently used for both the mini-car and snow mobile vehicles, and it is feasible to expand the SIDI engine application to also cover snow mobile applications, and achieve the demonstrated benefits of low emission, low fuel consumption and high engine output

Recently, society has demanded better performance from motorcycle regarding comfort, fuel economy, exhaust emission, and safety, in addition to traditional performance indicators. In the development of power trains, therefore, compact and lightweight hardware with improved transmission efficiency has been introduced, along with system technologies that optimize the engine revolution speed range and reduction ratio to suit driving conditions. This approach focuses on improving overall efficiency and addressing the issues of easier drivability and greater active safety. Electronic Controlled Continuously Variable Transmission (ECCVT) with high transmission efficiency is characterized by a Dry Hybrid Belt, in addition to an electronic controlled DC motor-driven shift mechanism, and an Electronic Controlled wet multi-plates Clutch (ECC).

The purpose of this study is to evaluate the effect of an exhaust throttle installed in an exhaust pipe in a two-stroke motorcycle engine. In the experimental study, the exhaust-throttle system prevented fresh-gas from short-circuiting and consequently, improved unburnt hydrocarbon emissions and fuel economy, along with enhancing combustion stability. In actual running, in order to minimize HC emission level and stabilize cycle-to-cycle fluctuation of combustion including intermittent misfiring, an air-induction system and a long-duration spark ignition were used in addition to the exhaust throttle system. The control software for the integrated system was also a key point in improving HC and CO emission levels in the ECE-40 operation cycle. For detecting misfiring in the ECE-40 cycle, time-resolved HC variation was measured by a fast-response gas analyzer.

Due to environmental problems, number of small vehicles with fuel efficiency increases. Since the small vehicles have small deformation space, it is difficult for them to achieve good crashworthiness at a frontal impact accident. Small deformation space usually yields high vehicle deceleration to absorb kinetic energy of the vehicle. The high vehicle deceleration may produce high occupant deceleration and lead to high occupant injury value. For example, North America, Japan and Europe specify head and chest injury value at vehicle's frontal collision. Those injury values tend to be improved if vehicle deceleration decreases. Deceleration of small vehicle with a little deformation space must be adjusted in order to prevent increase of the occupant injury value. A vehicle deceleration is expressed by 9, 18 or 36 discrete variables. A vehicle, an occupant and restraint systems such as seat belts are modeled by masses and a spring to simulate a frontal collision.

This study examines the effects of ethanol content on engine performances and the knock characteristics in spark ignition gasoline engine under various compression ratio conditions by cylinder pressure analysis, visualization and numerical simulation. The results confirm that increasing the ethanol content provides for greater engine torque and thermal efficiency as a result of the improvement of knock tolerance. It was also confirmed that increasing the compression ratio together with increasing ethanol content is effective to overcome the shortcomings of poor fuel economy caused by the low calorific value of ethanol. Further, the results of one dimensional flame propagation simulation show that ethanol content increase laminar burning velocity. Moreover, the results of visualization by using a bore scope demonstrate that ethanol affects the increase of initial flame propagation speed and thus helps suppress knock.