Search Results

A small four-stroke engine capable of all positional operation has been developed. The engine for hand held equipment provides easy maneuverability like two-stroke engines which are dominated in the small engine market. The developed technologies include the following items. ① 360° all positional operation by adopting a new lubrication system. ② Light-weight with a thin uni-block cylinder, etc. ③ Normal operation at more than 10,000 rpm and at low and medium revolution range are combined by high output with a wide torque band. Equally easy handling and better workability compared with the conventional two-stroke engines are achieved. In addition, better starting reliability, drastically improved emission, and half-reduction of running costs are also confirmed.

This report describes the engineering challenges in the development of 4 stroke 50ps outboard motor. The goal was set to attain the top speed and acceleration performance comparable to the existing 2 stroke versions, while providing the advantages of 4 stroke engine, including the alleviated exhaust odor and operational noise, as well as consistent performance with stable rpm. Emphasis was also given to the trolling at low rpm (at 650rpm). Our engineering challenges have been embodied into the 4 stroke outboard motor which is “clean” and yet allows similar application as existing 2 stroke versions.

Ryobi Outdoor Products (ROP) in Arizona, one of the subsidiaries of Ryobi Group of companies, developed 26.2cc OHV engine for string trimmers. (2) The outline of the valve train of this engine was presented at the SAE conference at Indianapolis 1996.(3) This paper describes methodologies and theoretical considerations by which such a unique valve train was developed. The theoretical consideration includes how optimize the valve train design to minimize the moving mass as a total system. Methodology for optimizing the design of each component of valve train is also presented. A review of how the theoretical optimization was translated into the final production engine design is given. The experimental effort to optimize cylinder head design to make the overall optimized design theory reality is described.

A control system for the intake flow on 4-stroke engines had been developed. It was named the VIP (Variable Intake Port) system. Such system was proved an effective strategy to achieve fast lean-bum at part load and to increase volumetric efficiency at wide open throttle. Test results showed that the maximum power of the VIP engine could rise more than 9 % in comparison with the original one. Under the ECE-40 test mode, this VIP motorcycle, without catalyst and secondary air system, could improve at least 16 % on fuel consumption. Emissions of HC+NOx was reduced from 1.07 to 1.00 g/km, and CO from 3.69 to 0.75 g/km. Not only the combustion variations at part load were improved, but also the maximum vehicle speed and the vehicle acceleration were superior to the original motorcycle.

Water emulsified hydrocarbon fuels substantially reduce pollutant emissions from internal combustion engines. Water emulsified gasoline, diesel, and naphtha mixtures, containing from 25 to 55% water, or more, have been successfully combusted in internal combustion engines. Because of the emulsified fuels lower energy content, a larger quantity of the emulsified fuel than of the equivalent base hydrocarbon fuel must be injected to obtain the same power output. However, based upon energy content, the emulsified fuel achieves higher thermal efficiency than the base hydrocarbon fuel.

A multi-layer catalyst comprising of a core of oxides of transition metals, an intermediate layer of an alumina- based silicate covering the core, and an outer layer of a noble metal alloy covering the intermediate layer was developed and was evaluated as to the reforming performance and its effects on fuel economy. The test results showed that the catalyst, with help of water contained in gasoline, can crack higher molecular hydrocarbons especially such a less combustible substance like aromatics to a lower molecular weight components, resulting in better combustion efficiency.

The object of this study is to evaluate the effects of air-head stratified scavenging with lean combustion using a 34cc two-stroke spark-ignition engine on reducing THC and CO emission and improving thermal efficiency. The result showed that the amount of short-circuiting mixture with a conventional Schnurle scavenging two-stroke engine was reduced from 30% to 9% with the air-head stratified scavenging two-stroke engine. Thermal efficiency was improved from 13.6% to 20.6%. As the result, the engine with air-head stratified scavenging in this study can conform to CARB 1999 or tier 2 emission standards regarding THC, CO and NOx emission.

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.

An experimental study was conducted to determine potential of natural gas in lowering exhaust emissions from small spark ignition engines. A single cylinder, four-stroke, air-cooled spark ignition engine was used in the study. The investigation showed that increasing engine compression ratio from 8:1 to 10:1 reduced penalty in power normally associated with natural gas engine. The engine was able to run very stable at equivalence ratio as lean as 0.65 while the same engine could not be run at equivalence ratio below 0.85 on gasoline. Best thermal efficiency and reduced emissions of hydrocarbons and oxides of nitrogen were realized around equivalence ratio 0.75. Reducing equivalence ratio further lowered emissions of oxides of nitrogen significantly while increase in hydrocarbons was small. Most of the hydrocarbons in exhaust were of the methane type which have low ozone forming reactivity.

Many nations have issued exhaust emission regulations for internal combustion engines not only for on road but also for off-road vehicles. In these regulations, several new exhaust gas sampling systems have been applied such as the direct sampling method (ISO 8178[1] / EPA Part.90[2] / EPA Part. 91[3]) and a revised methods from the existing regulation (SAE J 1088)[4]. The sampling method is a particularly noticeable change. Though we understand the necessity of having different regulations for different application engines, and have introduced several types of gas sampling systems for our analysis work, we expect to establish a common test procedure because we produce a wide range of different application engines for motorcycles, personal water crafts (PWC), all terrain vehicles (ATV) and small utility engines. We compared details of the emission data obtained from different sampling systems.

Five systems, fuel injection, ignition modulation, intake port flow control, exhaust after-treatment, and electric propulsion systems, are discussed here in terms of engine design modifications and new systems retrofitted to the motorcycle to reduce the exhaust emission. A fuel injection system has been implemented to a 125cc air-cool four-stroke engine, and the results show that the improvement on the fuel economy, reduction of emission on HC and CO, and the fuel economy are 20%, 68%, and 10% respectively. By implementing the electrical ignition system into the target engine, the fuel economy and emission have slightly improved. The application of the inlet air flow control to a target engine also obtains 75% on CO reduction. The effectiveness of the exhaust after-treatment on a 80cc 2-stroke engine has demonstrated that the emission can be reduced up to 75%.

From a view point of reducing exhaust emission level on a small utility 4-stroke spark-ignition engine, this paper describes the exhaust emission materials analysis and the affect against California Air Resources Board (CARB) specified testing mode on a new prototype while applying very lean mixture burning. The combustion chamber shape and the intake air passage of a production model (Displacement 286 cc, 4-stroke, air cooled, over head valve (OHV), single cylinder) was modified and optimized on the prototype to achieve a stable run up to a lean air-fuel ratio of 20 : 1. When the air-fuel ratio was changed, the highest density of NOx was a little higher than 3,000ppm at an air-fuel ratio of 16 : 1 and the lowest was about 300 ppm at an air-fuel ratio of 19 : 1. The emission level of THC was a little higher than 2,000ppm at an air-fuel ratio of 12 : 1 and less than 1,000 ppm at an air-fuel ratio of 15 : 1 and higher.

Snowmobile engine emissions are of concern in environmentally sensitive areas, such as Yellowstone National Park (YNP). A program was undertaken to determine potential emission benefits of use of bio-based fuels and lubricants in snowmobile engines. Candidate fuels and lubricants were evaluated using a fan-cooled 488-cc Polaris engine, and a liquid-cooled 440-cc Arctco engine. Fuels tested include a reference gasoline, gasohol (10% ethanol), and an aliphatic gasoline. Lubricants evaluated include a bio-based lubricant, a fully synthetic lubricant, a high polyisobutylene (PIB) lubricant, as well as a conventional, mineral-based lubricant. Emissions and fuel consumption were measured using a five-mode test cycle that was developed from analysis of snowmobile field operating data.

The purpose of this study is to examine the cause of combustion fluctuation in a partially loaded two-stroke engine with respect to the hydrocarbon (HC) concentration in the cylinder. HC concentration in the cylinder, exhaust gas velocity and pressure were simultaneously measured in order to determine the influence of HC concentration on combustion fluctuation. A correlation between cyclic variation in HC concentration in the cylinder and IMEP was confirmed. The way in which the HC concentration influenced the combustion states in the next cycle made clear. A decrease of HC concentration cause the delay of early flame development and combustion, the decrease of HC concentration had an great influence on the combustion states. The relationship between combustion states and HC concentration was discussed. The relative value of IMEP and HC concentration were closely related to the HC concentration in the cylinder.

The classical two-stroke engine is well known for its mechanical simplicity, its high power-to-weight ratio but also, unfortunately, for its poor fuel utilization effectiveness due to large losses of fuel during scavenging leading to a high specific consumption and a high hydrocarbon pollution rate. A very simple system, called Delayed-Charging (D.-C.), was proposed in earlier papers, improving fuel utilization by separating the scavenging and charging functions, the latter being retarded. In this paper, comparisons are made between a 50 cc production engine and D.-C. modified 50 cc engines equipped with a pressurized carburetter or a low-pressure injector feeding the air flow into the charging-transfer duct (i.e. various engines including parameter changes such as injector location, fuel jet angle, jet direction, injection closing angle, D.C.-transfer duct geometry, number of scavenging transfer ducts,…).

The advantages of air assisted direct fuel injection systems to achieve high atomization degree into the combustion chamber of SI engines are well-known. The solutions up to now proposed appear anyway poorly tailored to be suitable for small engine applications. In fact scaling down such existing systems for automotive applications, they present mainly two drawbacks: the costs and a difficult tuning of the very low quantity of fuel required per cycle. Moreover the amount of electric energy required makes the engines not self-sufficient. To overcome the above mentioned problems, Piaggio has developed a completely mechanical low cost fuel injection system, named FAST (Fully Atomized Stratified Turbulence), which does consent a very atomized and stratified mixture lean combustion process, i.e. a dramatic improvement of emissions and fuel consumption. After general considerations, the application of such system to a small capacity 2T engine is analyzed.

Air Assisted Direct in-cylinder injection systems have now been in commercial production for over 18 months in large two-stroke outboard applications, offering the customer the advantage of emissions control, significant fuel economy improvements, smooth and misfire-free operation and improved driveability. With the pending implementation of emission controls in most two-stroke engine applications, the fuel system of choice must be capable of being adapted in a short time period to a new or given application. Over the last three years, the air assisted direct injection system has been successfully applied across a range of cylinder displacements from 50 to 500cc. In all applications, the in-cylinder injection system's hardware has been maintained common in order to share in the benefits of economies of high volume production.

This paper deals with a controllable small vibration-proof mount designed for precision devices equipped on cars and other transportation vehicles. The properties of this mount can be controlled by the applied electric field strength, and this is one of application studies of electrorheological(ER) fluid. Liquid crystal is a homogeneous organic compound characterized by molecular orientation responsding to external electric or magnetic field, and because of molecular orientation, its viscosity can be varied by the applied electric field. In the present paper, a mount of small size designed for mass-produced vehicles is constructed and its performance was investigated. It is shown experimentally that the vibration amplitude of a mass supported by the present mount can be decreased by changing the damping properties.

Motor vehicle noise is regulated by the pass-by provisions of ISO 362. Although motorcycle noise levels have fallen significantly, in line with the legal requirements, there is still a difference between noise levels for new and in-use vehicles. A research program was initiated to compare in-use motorcycle operating conditions with the requirements of the pass-by test. Ten current production motorcycles were monitored during actual urban driving conditions in several European cities during various driving periods. The results show the pass-by provisions of ISO 362 do not reflect actual in-use operating characteristics of modern motorcycles. To be representative, the test procedure should be based on engine rpm and not vehicle speed.

The Two-Stroke engine revival is seen as a way to reduce the size and weight of engines. IFP has been one of the first engine research centres involved since the early eighties in this promising way of a new generation of highly efficient engines. Since this date, a large number of car manufacturers and research laboratories around the world have engaged research and development efforts in this new field. In these conditions, it was essential for IFP to examine the different research works, technological choices, and new ideas. The systematic study of the patents published since 1981 and their statistical analysis represent an interesting tool to follow the main trends of the research in this domain. More than 4200 patents were selected as relevant for this study.