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Honda has developed a new hybrid system targeting the C and D segments that aims for the latest environmental performance, high fuel economy, and enhanced acceleration feeling in driving. The new engine to be applied to this new hybrid system has been developed with the goal of expanding the high thermal efficiency range, realizing the latest environmental performance, and high quietness. The new engine has adopted the Atkinson cycle and cooled exhaust gas recirculation (EGR) carried over from the previous model [1], and employed an in-cylinder direct fuel injection system with fuel injection pressure of 35 MPa. The combustion chamber and ports have been newly designed to match the fuel system changes. By realizing high-speed combustion, the engine realized a high compression ratio with the mechanical compression ratio of 13.9.

We studied a simple and cost effective controlled auto ignition (CAI) combustion engine in order to achieve simultaneous reduction of NOx and soot, which are issues in diffusion combustion. The engine type was a uniflow scavenging 2-stroke engine, and the fuel used was diesel, as is common in diesel engines. We examined the position of the injector that effectively forms the premixture and realized stable operation with diesel fuel by the low pressure fuel injection device for port fuel injection (PFI), and it was found that the CAI combustion ignition timing can be controlled through setting the air/fuel ratio that obtains the optimal ignition timing per operation conditions.

A variable cooling system has been developed for scooters equipped with an air cooled, four-stroke, single cylinder gasoline engine. This system opens or closes louver located at the cooling air inlet using an oil-temperature sensitive actuator. When the engine is cold or the engine load is low, the louver shut off the cooling air for a quick warm-up and for maintaining the engine oil temperature high to reduce the friction losses that occur with low oil temperature while eliminating the loss from driving the cooling fan as well. The quick warm-up also decreases supplementary fuel injections necessary when the engine is cold. Consequently, fuel economy improvement by 3.3% was realized in running condition of the Urban Driving Cycle.

In a modern diesel engine, a high fuel injection pressure is achieved by a common-rail system. Therefore, it is important to understand the effects of fuel properties on engine performances because a diesel fuel could deteriorate inside an injector at such severe conditions. The test methods so far basically use the fuel with pro-fouling agent to form deposit on injector. In this study, a novel test procedure was developed to evaluate the effect of the use of the fuel with and without zinc contaminant on injector performance. With Zn doped European specification B7 fuel (7% biodiesel) as a reference, the test result showed that an engine torque decreased almost lineally over time, and the overall torque drop was 9% after 300 hours. The investigation of the dismantled injector after the test revealed that the deposit was not formed on the sliding parts of the injector, but on the nozzle hole surface.

Recently, the electronic fuel injection systems have been widely applied to small motorcycles including scooters. In the high pressure fuel lines, plastic hoses have been increasingly used instead of conventional rubber hoses. As the plastic hose is less elastic than the rubber hose, the fuel pressure pulsates more in the plastic hose. To cope with this issue, we have conducted researches on how the fuel pressure pulsation in the plastic hose affects the accuracy of fuel injection. Keeping our eyes on the pulsation damping effects derived from the changes of volume due to the expansion and contraction of hose when the pressure changes, we have established the analysis method for optimization of the inner diameter and the thickness of the hose utilizing CAE analysis. The newly-developed plastic hose is applicable to motorcycles having a single cylinder 250 cm3 engine using an injector of a high static flow rate.

A new control system using O₂ feedback control has been developed as an alternative to intake air pressure sensors. This control method uses the operational condition compensation coefficient Kbu. This coefficient encompasses the state of the engine and environmental conditions such as atmospheric pressure, and corrects fuel injection in response to changes in these factors. Kbu makes it possible to control the amount of fuel injection without depending on an intake air pressure sensor. It also makes it possible to carry out the appropriate air-fuel ratio correction even at times when O₂ feedback control is not operating, such as the cold period, when the engine is first started, or during transient operation, by using Kbu values recorded in the Engine Control Unit (henceforth ECU).

The field of diesel combustion research is producing numerous reports on studies of premixed combustion, which promises simultaneous reduction of both NOx and soot, in order to meet increasingly stringent regulations on harmful emissions from automobiles. However, although premixed combustion can simultaneously reduce both NOx and soot, certain issues have been pointed out, including the fact that it emits greater quantities of unburned HC and CO gases and the fact that it limits the operating range. Furthermore, this combustion method sets the ignition delay longer with the aim of promoting the mixing of fuel and air. This raises issues with the product due to the combustion instability and sensitivity to the uneven fuel properties that are found on the market, the capability of the engine response under transient conditions, the deterioration in combustion noise, and so on.

In an attempt to decrease the amount of CO2 emitted by engines and yet improve engine output power, various approaches to the development of variable valve-lift mechanisms and the application of direct fuel injection and supercharger mechanisms are rapidly gaining popularity. In the case of the swing motion which takes place in variable valve-lift mechanisms, the relative speed between the two components reaches zero at the location where the load is high and the oil film tends to break, thereby leading to wear. Furthermore, the use of a supercharger and a direct injection device generates soot, which promotes further wear. Therefore establishing a reliable method for estimating wear has become a pressing issue. Wear problems caused by the swing motion occur during boundary lubrication, and we have devised a solution for them.

Homogeneous Charge Compression Ignition (HCCI) combustion shows a high potential of reducing both fuel consumption and exhaust gas emissions. Many works have been devoted to extend the HCCI operation range in order to maximize its fuel economy benefit. Among them, fuel injection strategies that use fuel reforming to increase the cylinder charge temperature to facilitate HCCI combustion at low engine loads have been proposed. However, to estimate and control an optimal amount of fuel reforming in the cylinder of an HCCI engine proves to be challenging because the fuel reforming process depends on many engine variables. It is conceivable that the amount of fuel reforming can be estimated since it correlates with the combustion phasing which in turn can be measured using a cylinder pressure sensor.

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.

A fully flexible valve actuation (FFVA) system was developed for a single cylinder research engine to investigate high efficiency clean combustion (HECC) in a diesel engine. The main objectives of the study were to examine the emissions, performance, and combustion characteristics of the engine using late intake valve closing (LIVC) to determine the benefits and limitations of this strategy to meet Tier 2 Bin 5 NOx requirements without after-treatment. The most significant benefit of LIVC is a reduction in particulates due to the longer ignition delay time and a subsequent reduction in local fuel rich combustion zones. More than a 95% reduction in particulates was observed at some operating conditions. Combustion noise was also reduced at low and medium loads due to slower heat release. Although it is difficult to assess the fuel economy benefits of LIVC using a single cylinder engine, LIVC shows the potential to improve the fuel economy through several approaches.

With increasingly stringent emissions regulations and concurrent requirements for enhanced engine thermal efficiency, a comprehensive characterization of the automotive gasoline fuel spray has become essential. The acquisition of accurate and repeatable spray data is even more critical when a combustion strategy such as gasoline direct injection is to be utilized. Without industry-wide standardization of testing procedures, large variablilities have been experienced in attempts to verify the claimed spray performance values for the Sauter mean diameter, Dv90, tip penetration and cone angle of many types of fuel sprays. A new SAE Recommended Practice document, J2715, has been developed by the SAE Gasoline Fuel Injection Standards Committee (GFISC) and is now available for the measurement and characterization of the fuel sprays from both gasoline direct injection and port fuel injection injectors.

General Motors' 3.6L DOHC 4V V6 engine has been upgraded to provide substantial improvements in performance, fuel economy, and emissions for the 2008 model year Cadillac CTS and STS. The fundamental change was a switch from traditional manifold-port fuel injection (MPFI) to spark ignition direct injection (SIDI). Additional modifications include enhanced cylinder head and intake manifold air flow capacities, optimized camshaft profiles, and increased compression ratio. The SIDI fuel system presented the greatest opportunities for system development and optimization in order to maximize improvements in performance, fuel economy, and emissions. In particular, the injector flow rate, orifice geometry, and spray pattern were selected to provide the optimum balance of high power and torque, low fuel consumption, stable combustion, low smoke emissions, and robust tolerance to injector plugging.

Bio-ethanol is one of the candidates for automotive alternative fuels. For reduction of carbon dioxide emissions, it is important to investigate its optimum combustion procedure. This study has explored effect of ethanol fuels on HCCI-SI hybrid combustion using dual fuel injection (DFI). Steady and transient characteristics of the HCCI-SI hybrid combustion were evaluated using a single cylinder engine and a four-cylinder engine equipped with two port injectors and a direct injector. The experimental results indicated that DFI has the potential for optimizing ignition timing of HCCI combustion and for suppressing knock in SI combustion under fixed compression ratio. The HCCI-SI hybrid combustion using DFI achieved increasing efficiency compared to conventional SI combustion.

Diesel emissions are significant issue worldwide, and emissions requirements have become so tough that. the application of after-treatment systems is now indispensable in many countries To meet even more stringent future emissions requirements, it has become apparent that the improvement of market fuel quality is essential as well as the development in engine and exhaust after-treatment technology. Japan Clean Air Program II (JCAP II) is being conducted to assess the direction of future technologies through the evaluation of current automobile and fuel technologies and consequently to realize near zero emissions and carbon dioxide (CO2) emission reduction. In this program, effects of fuel properties on the performance of diesel engines and a vehicle equipped with two types of diesel NOx emission after-treatment devices, a Urea-SCR system and a NOx storage reduction (NSR) catalyst system, were examined.

In an attempt for further improvement of exhaust gas purification and fuel economy, an electronically controlled fuel injection (FI) system has been applied to small size motorcycles. As compared to a similar system for cars, FI systems for small two wheeled vehicles are required to be small, lightweight and low cost. In order to meet these requirements, authors developed a new control method of determining the required quantity of fuel. This system removes the intake pressure sensor of the intake pipe that exists in the conventional FI system. From correlating the peak intake pressure in the intake pipe with the quantity of intake air closely, the peak intake pressure is estimated by using rotation change of the crankshaft. The required quantity of fuel is injected into the engine intake pipe determined by the map set up in the peak intake pressure and the fuel injection period.

As technologies for simultaneously maintaining the current high thermal efficiency of diesel engines and reducing particulate matter (PM) and nitrogen oxide (NOX) emissions, many new combustion concepts have been proposed, including premixed charge compression ignition (PCCI) and low-temperature combustion[1]. However, it is well known that since such new combustion techniques precisely control combustion temperatures and local air-fuel ratios by varying the amount of air, the exhaust gas recirculation (EGR) ratio and the fuel injection timing, they have the issues of being less stable than conventional combustion techniques and of performance that is subject to variance in the fuel and driving conditions. This study concerns a system that addresses these issues by detecting the ignition timing with in-cylinder pressure sensors and by controlling the fuel injection timing and the amount of EGR for optimum combustion onboard.

A rapid prototyping controller (RPC) based, full-authority, diesel control system is developed, implemented, tested and validated on FTP cycle. As rapid prototyping controller, dSPACE Autobox is coupled with a fast processor based slave for lower level I/O control and a collection of in-house designed interface cards for signal conditioning. The base software set implemented mimics the current production code for a production diesel engine. This is done to facilitate realistic and accurate comparison of production algorithms with new control algorithms to be added on future products. The engine is equipped with all the state-of-the art subsystems found in a modern diesel engine (common rail fuel injection, EGR, Turbocharger etc.).

The combustion simulation based on CFD (Computational Fluid Dynamics) was attempted in order to visualize in-cylinder combustion phenomena of a small displacement, high speed four-stroke SI engine for motorcycle applications. To verify the results of the simulation, the steady state flow in a cylinder, the fuel spray behavior and the flame propagation behavior in an actual engine were measured and compared. The results were that an adequate correlation was confirmed in each phenomenon, proving that the CFD was applicable as a means of visualization. As the result of the investigation of the combustion system applying this technique, improvements such as the specific fuel consumption and the extension of the lean combustion zone were attained, assuring effectiveness of this technique for actual engine development. This technique has been applied to the development of the world's first four-stroke 50cm3 PGM-FI (Programmed Fuel Injection) engine.

This emission reduction technique has been researched on motorcycles equipped with a four-cylinder, liquid-cooled engine of 1100cm3 displacement in order to comply with the EURO-3 emission regulation. The EURO-3 emission regulation will be enforced in Europe beginning in year 2006. Compared to the EURO-2 regulation, reduction of cold-start HC and reduction of NOx from the extra-urban driving cycle are the main issues for EURO-3 compliance. The hydrocarbon reduction during cold-starting was achieved by the method of early catalyst activation using a combination of an Idle Air Control Valve system (IACV), ignition-retard, and atomization of fuel spray. In the extra-urban driving cycle, the fine controlled air-fuel ratio reduced. In addition, optimization of the number of three-way catalyst cells and their capacity also reduced NOx. Moreover, power loss decline caused by increased exhaust resistance due to increasing the catalyst size was avoided by optimizing the catalyst location.