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The effect of low level ethanol fuel on the power and emissions characteristics was studied in a small, mass produced, carbureted, spark-ignited, Briggs and Stratton Vanguard 19L2 engine. Ethanol has been shown to be an attractive renewable fuel by the automotive industry; having anti-knock properties, potential power benefits, and emissions reduction benefits. With increasing availability and the possible mandates of higher ethanol content in pump gasoline, there is interest in exploring the effect of using higher content ethanol fuels in the small utility engine market. The fuels in this study were prepared by gravimetrically mixing 98.7% ethanol with a balance of 87 octane no-ethanol gasoline in approximately 5% increments from pure gasoline to 25% ethanol. Alcor Petrolab performed fuel analysis on the blended fuels and determined the actual volumetric ethanol content was within 2%.

The technology to estimate engine load using the amplitude of crankshaft angular velocity variation during a cycle, which is referred to as “Δω (delta omega)”, in a four-stroke single-cylinder gasoline engine has been established in our former studies. This study was aimed to apply this technology to the spark advance control system for small motorcycles. The cyclic variation of the Δω signal, which affects engine load detection accuracy, was a crucial issue when developing the system. To solve this issue, filtering functions that can cope with various running conditions were incorporated into the computation process that estimates engine loads from Δω signals. In addition, the system made it possible to classify engine load into two levels without a throttle sensor currently used. We have thus successfully developed the new spark advance system that is controlled in accordance with the engine speed and load.

The feeling given through the vibration, which is transiently generated by the body when the throttle is beginning to be opened, is one of the important factors that affect the quality of drivability in motorcycles. This feeling is usually evaluated by subjective ratings on actual motorcycles carried out by expert riders and the specifications are decided based on those results. In this research, the subjective rating was expressed as a formula and the simulation technology of behavior prediction was constructed for the parts associated with the drive train as well as the motorcycle body. The responding time delay, the magnitude of overshoot and the vibration frequencies were extracted as highly correlated factors with the evaluation results of subjective ratings through the analysis on the characteristics of longitudinal acceleration responses of the body to the magnitude of throttle opening.

Honda R&D has developed a throttle-by-wire (TBW) system that meets the needs of motorcycles where the attitude of the vehicle body is controlled by operation of the throttle. To gain high response and following for the throttle valve, we employed a new adaptive control algorithm. The newly developed system has an idling combustion stabilization function and a three-dimensional control function for the throttle-opening map based on running gear and engine speed. With those functions, we improved the controllability of the motorcycle, especially for small throttle openings. Furthermore, we improved the feeling of the limiter control used in maximum-speed limitation. For the overall system, intake system related devices are consolidated to improve the layout flexibility and expand the mounting options on the motorcycle.

Recently, emission regulations have been strict in many countries, and it is very difficult technical issue to reduce emissions of diesel cars. In order to reduce the emissions, various combustion technologies such as Massive EGR, PCCI, Rich combustion, etc. have been researched. The combustion technologies require precise control of the states of in-cylinder gas (air mass flow, EGR rate etc.). However, a conventional controller such as PID controller could not provide sufficient control accuracy of the states of in-cylinder gas because the air-pass system controlled by an EGR valve, a throttle valve, a variable nozzle turbo, etc. is a multi-input, multi-output (MIMO) coupled system. Model predictive control (MPC) is well known as the advanced MIMO control method for industrial process. Generally, the sampling period of industrial process is rather long so there is enough time to carry out the optimization calculation for MPC.

The purpose of this research is to develop a prediction technique that can be used in the development of port fuel-injection (hereinafter called PFI) gasoline engines, especially for general purpose small utility engines. Utility engines have two contradictory desirable aspects: compactness and high-power at wide open throttle. Therefore, applying the port fuel injector to utility engines presents a unique intractableness that is different from application to automobiles or motorcycles. At the condition of wide open throttle, a large amount of fuel is required to output high power, and injected fuel is deposited as a wall film on the intake port wall. Despite the fuel rich condition, emissions are required to be kept under a certain level. Thus, it is significant to understand the wall film phenomenon and control film thickness in the intake ports.

New Generation Advanced Hydraulic-Mechanical Transmission (A-HMT) with the Lock-Up mechanism and the automatic start clutch mechanism was developed. In the lock-up mechanism, an electronic control in conjunction with transmission control was adopted using oil temperature, throttle opening, and input / output rotation ratio as parameter to reduce a rotational energy change of input and output axis caused by the volumetric efficiency of A-HMT. In the automatic start clutch, the load sensing function, damper function, and cooling function by replacing the simple hydraulic mechanism are equipped. By these solutions, the transmission efficiency has enhanced approximately 10% compared with former A-HMT, and excellent starting performance and smooth transmission performance have achieved.

In most motorcycle engines, blow-by gas is introduced into the air intake system, including the air cleaner, for the purpose of reducing the blow-by gas emissions in the crankcase. In such a system, the water and gasoline components of the blow-by gas get mixed into the engine oil under some driving conditions. This oil contamination shortens the oil replacement intervals. In order to reduce this problem, we devised a system to ventilate the crankcase positively and installed it on the engine of a small motorcycle. The system had a construction to draw fresh air with a one way valve that is actuated by the change in pressure inside the crankcase. The inside of the crankcase is ventilated by the fresh air. In the case of small motorcycle engines, if the gas positively ventilated from the inside of the crankcase were guided to the downstream of the throttle valve, the engine performance under low -loads, including idling, is significantly changed by the inflow of the gas.

Gas-phase in-cylinder mixing was examined by two different methods. The first method for observing mixing involved planar Mie scattering measurements of the instantaneous number density of silicon oil droplets which were introduced to the in-cylinder flow. The local value of the number density was assumed to be representative of the local gas concentration. Because the objective was to observe the rate in which gas concentration gradients change, to provide gradients in number density, droplets were admitted into the engine through only one of the two intake ports. Air only flowed through the other port. Three different techniques were used in analyzing the droplet images to determine the spatially dependent particle number density. Direct counting, a filtering technique, and autocorrelation were used and compared. Further, numerical experiments were performed with the autocorrelation method to check its effectiveness for determination of particle number density.

A direct calibration has been performed on laser-induced fluorescence measurements of the oil film in a single cylinder air-cooled research engine by simultaneously measuring the minimum oil film thickness by the capacitance technique. At the minimum oil film thickness the capacitance technique provides an accurate measure of the ring-wall distance, and this value is used as a reference for the photomultiplier voltage, giving a calibration coefficient. This calibration coefficient directly accounts for the effect of temperature on the fluorescent properties of the constituents of the oil which are photoactive. The inability to accurately know the temperature of the oil has limited the utility of off-engine calibration techniques. Data are presented for the engine under motoring conditions at speeds from 800 - 2400 rpm and under varying throttle positions.

A laboratory-based fuel mixture system capable of delivering a range of fuel/air mixtures has been used to observe the effects of differing mixture characteristics on engine combustion through measurement and analysis of incylinder pressure and exhaust emissions. Fuel air mixtures studied can be classified into four different types: 1) Completely homogeneous fuel/air mixtures, where the fuel has been vaporized and mixed with the air prior to entrance into the normal engine induction system, 2) liquid fuel that is atomized and introduced with the air to the normal engine induction system, 3) liquid fuel that is atomized, and partially prevaporized but the air/fuel charge remains stratified up to introduction to the induction system, and 4) the standard fuel metering system. All tests reported here were conducted under wide open throttle conditions. A four-stroke, spark-ignited, single-cylinder, overhead valve-type engine was used for all tests.

To enable non-throttling operation of gasoline S.I. engine, we have manufactured engines equipped with a newly developed Hydraulic Variable-valve Train (HVT), which can vary its intake-valve closing-timing freely. The air-intake control ability of HVT engine is equivalent to conventional throttling engines. Combustion becomes unstable, however, under non-throttling operation at idling. For the countermeasure, newly designed combustion chamber has been developed. The reduction of pumping loss by the HVT depends on engine speed rather than load, and amounts to about 80 % maximum. A conventional engine-management system is not applicable for non-throttling operation. Therefore, new management system has been developed for load control.

An electronically controlled fuel injection system for controlling the air/fuel (A/F) ratio has been looked forward as a means for improving drivability, output characteristics, and fuel consumption of two-stroke cycle motorcycle racer engines. However, actual installation of such a system on a high output two-stroke cycle engine (which utilizes exhaust gas pressure pulsation effects) has been considered difficult for the following reasons. Fluctuation in the delivery ratio (L) during firing and misfiring becomes great due to effects from the exhaust pipe. Applying the control method used for conventional four-stroke cycle engines (by which the delivery ratio (L) is measured) would necessitate a large and heavy system. The authors have eliminated such problems by developing an electronically controlled fuel injection system, the PGM-FI (Programmed-Fuel Injection) system, which employs basic intake air flow data according to engine speed (NE) and throttle opening (θTH).