Search Results

An electronically controlled closed-loop carburetor system has been developed. This system's air-fuel ratio control is characterized by the air bleeds being controlled by turning the solenoid valves on and off at a constant frequency. The frequency above 30 Hz was desirable for practical performances. Some improvements and developments were made to the carburetor, the solenoid valve and the control unit. In application of this system to a three-way catalytic system with O2 sensor, the emissions met the 1978 Japanese standards.

A theoretical and experimental vibration analysis was carried out on the vehicle equipped with independent rear suspension in order to reduce the interior noise. As the results it is confirmed that the following items have the great effects on the transmission of exciting force; namely: (l) Coil-spring location (2) Dynamic stiffness of mounting insulator (3) Rigidity of suspension-member (4) Rigidity of body structure where suspension is mounted These results were applied to the actual new type of vehicle and its interior noise was measured and three-four dB (A) of noise reduction was obtained.

In order to study the potentiality of the modification of the combustion rate for NOx formation control in the spark ignition (SI) engine, the authors first developed a new mathematical model by assuming the stepped gas temperature gradient in the cylinder. The predicted results from this new mathematical model show good coincidence with the experimental data. Second, the authors discuss the effects of the modification of the combustion rate on NOx formation using the new mathematical model. It was concluded that NOx formation in the premixed SI engine would be essentially determined by the specific fuel consumption only, regardless of any modification of the engine combustion rate.

The Inter-Industry Emission Control (IIEC) Program included the thermal reactor as one of the effective ways of oxidizing HC and CO in the exhaust system. However, this was accompanied by very substantial fuel economy penalties, especially in the case of small engine-low emission concept vehicles. Starting with a new concept aimed at obtaining the HC/CO oxidizing trigger temperature in the thermal reactor by modifying engine settings, the authors arrived at an economical technique of matching the thermal reactor to the engine.

Misfire and cycle-to-cycle combustion variation are both serious problems in securing good engine performance and low exhaust emissions in the case of using extremely lean mixtures. Making some modifications in the ignition system and in the combustion chamber, and increasing the mixture turbulence, we examined their effects upon the lean limit, the engine performance, and the exhaust emissions. It was found that gap width and gap projection of a spark plug and spark energy as well as mixture turbulence had a great effect on extending the lean limit and improving engine performance with lean mixtures. A compact combustion chamber is preferable for lean mixture operation. Smooth operation of the engine can be maintained even at retarded spark timing by applying the above-mentioned items and providing hot intake air to the engine. Consequently, exhaust emissions, including hydrocarbons and oxides of nitrogen, can be substantially reduced.

Earlier work has demonstrated that exhaust gas recirculation (EGR) decreases peak combustion temperature and thus reduces the concentration of nitrogen oxides (NOx) in spark ignition engine exhaust. The present authors hypothesized that NOx formation is primarily affected by the heat capacity of the combustion gases and recycled exhaust. The hypothesis was tested in an experimental program involving the admission of inert gases such as He, Ar, H2, and CO2, and water in place of EGR. In addition to confirming the validity of the original hypothesis, the test data also indicated that engine output and efficiency were significantly affected by the heat capacity of the combustion gases. The authors conclude that EGR functions by increasing the heat capacity of the working fluid, and demonstrates that the correlative changes in NOx and engine performance can be predicted from heat capacity considerations.

Three Japanese automobile manufacturers-Mitsubishi Motors Corp., Nissan Motor Co., Ltd., and Toyo Kogyo Co., Ltd.-have been making efforts over the past three years to design and develop effective thermal reactor-exhaust gas recirculation and catalytic converter systems suitable for small engines. The work is being done by members participating in the IIEC (Inter-Industry Emission Control) Program, and the exhaust emission levels of the concept vehicles developed by these companies have met the goal established by the IIEC Program at low mileage. Each system, however, has a characteristic relationship between exhaust emission level and loss of fuel economy. Much investigation is required, particularly with respect to durability, before any system that will fully satisfy all service requirements can be completed. This paper reports the progress of research and development of the individual concept vehicles.

Fatigue tests on a body in white have been made with torsional load and compared with previous results for assessments, where it was difficult to agree with proving ground tests in evaluating the life. Modifying the above mentioned fault, a programmed fatigue test method on the body in white is presented in this paper. The newly developed programmed fatigue test method is the simultaneous loading of the bouncing and torsional modes to a body in while by an electrohydraulic fatigue testing machine in accordance with the programmed sprung mass accelerations. Applying this method, the comparatively accurate assessment of proving ground test was made at the condition of the body in white, and the development period for body construction was shortened.