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The volatile organic compounds (VOC) from diesel engines, including formaldehyde and benzene, are concerned and remain as unregulated harmful substances. The substances are positively correlated with THC emissions, but the VOC and aldehyde compounds at light load or idling conditions are more significant than THC. When coolant temperatures are low at light loads, there are notable increases in formaldehyde and acetaldehyde, and with lower coolant temperatures the increase in aldehydes is more significant than the increase in THC. When using ultra high EGR so that the intake oxygen content decreases below 10%, formaldehyde, acetaldehyde, benzene, and 1,3-butadiene increase significantly while smokeless and ultra low Nox combustion is possible.

Since in-cylinder flame temperature has a direct effect on an engine's NOx characteristics, these phenomena have been studied in detail in a DI diesel engine using a newly developed method allowing the in-cylinder temperature distribution to be measured by the two color method. The flame light introduced from the visualized combustion chamber of the engine is divided into two colors by filters. The images of combustion phenomena using the two wavelengths are recorded with a framing streak camera which includes a CCD camera. The flame temperature is immediately calculated by a computer using two color images from the CCD camera. A parameter study was then carried out to determine the influence of intake valve number of the engine, and fuel injection rate (pilot injection) on the in-cylinder temperature distribution.

The Hino E13C was developed for heavy-duty truck application to meet Japan's 2003 NOx and 2005 particulate emissions standards simultaneously with significant fuel economy improvement. A combined EGR system consisting of an external EGR system with a highly efficient EGR cooler and an internal EGR system with an electronically controlled valve actuation device was newly developed to reduce NOx emissions for all operating conditions without requiring a larger engine coolant radiator. A Hino-developed DPR was installed to achieve extremely low particulate emissions at the tail pipe. Increased strength of engine structural components and a ductile cast iron piston enabled high BMEP operation at lower engine speeds and reductions of both engine size and weight. This paper describes key technologies developed for the E13C as well as the development results.

Since in-cylinder flame temperature has a direct effect on an engine's NOx characteristics, this phenomena has been studied in detail in a multi-cylinder DI diesel engine using a new method allowing the in-cylider temperature distribution to be measured by the two color method. An endoscope is installed in the combustion chamber and flame light introduced from the endoscope is divided into two colors by filters. The images of combustion phenomena using the two wavelengths are recorded with a framing streak camera which includes a CCD camera. The flame temperature and KL factor are immediately calculated by a computer using the two color images from the CCD camera. In the case of EGR, the test was conducted under 75% load conditions. The flame temperature was reduced according to an increase of EGR rate.

In Biodiesel Fuel Research Working Group(WG) of Japan Auto-Oil Program(JATOP), some impacts of high biodiesel blends have been investigated from the viewpoints of fuel properties, stability, emissions, exhaust aftertreatment systems, cold driveability, mixing in engine oils, durability/reliability and so on. This report is designed to determine how high biodiesel blends affect oil quality through testing on 2005 regulations engines with DPFs. When blends of 10-20% rapeseed methyl ester (RME) with diesel fuel are employed with 10W-30 engine oil, the oil change interval is reduced to about a half due to a drop in oil pressure. The oil pressure drop occurs because of the reduced kinematic viscosity of engine oil, which resulting from dilution of poorly evaporated RME with engine oil and its accumulation, however, leading to increased wear of piston top rings and cylinder liners.

In the Japanese heavy duty truck market, demands of improved fuel economy and lighter vehicles to increase load capacity, and further improvements in emissions are constantly increasing. To satisfy these requirements, basically a smaller sized and higher boosted diesel engine is effective, because such an engine has a compact size and light weight, and shows improved fuel consumption due to a relatively lower frictional loss. On the basis of this concept Hino introduced the original EP100 in 1981 as the first Japanese turbocharged and air to air charge-cooled engine. Since then Hino has made many efforts to improve the engines and develop new technologies.

In a tractor-trailer, ride comfort affected by horizontal human body motions, so called “wavy” and “shaky” feelings, is at issue. Insight about “wavy” and “shaky” feelings which is important for efficient vehicle development is not enough. Experiments using 6-axis motion generator and motion capture and inverse-analysis using multi-body human model indicated the characteristics of each feeling. Motion observation and transfer function indicated that while a bad subjective score of “wavy” feeling corresponds to same-phase roll motion of chest and pelvis up to 0.7Hz, “shaky” correlates to an antiphase of them around 2Hz. By multiple regression, dominant vibration components of the human body and the vehicle to subjective evaluation of the feelings above were identified. Explanatory variables for the “wavy” feeling are roll rate and lateral jerk and those for the “shaky” are lateral acceleration and longitudinal acceleration.

In this paper, the flow patterns and velocity distributions of coolant flow around cylinder liners of diesel engine are studied by numerical calculation and experimental observation. The experiment is carried out by oil film method and direct observation with a transparent acrylic cylinder liner. The calculation is performed with the 3-dimensional model by FEM for fluid flow. The motion of coolant flow by calculation corresponds with the result by oil film method and direct observation with transparent cylinder liner. The visualization of the 3-dimensional calculation gives a good understanding about motion of coolant flow and pressure distribution in water chamber. This method is applied to improve the coolant flow with the stagnation around cylinder liner. The effect of improved design is confirmed by experiment. That is, there are no stagnations in the flow around cylinder liners.

The noise-generating mechanism of a reciprocating air compressor for heavy duty vehicles during idling was investigated. It was elucidated that the gear rattling noise of the air compressor drive gear train caused by the negative value of the air compressor drive torque was a major noise source. To completely suppress the gear rattling phenomenon, a new loading device with an air cylinder that cancels the negative value of the air compressor drive torque was fabricated. When the loading device was worked, the impulsive sound level was reduced to 10 dB(A). It was found that the impulsive sound level during gear rattling is closely related to the difference in gear teeth velocity between the crankshaft gear and the air compressor drive gear, as one of the characteristics that are needed to obtain a guide for carrying out estimations in the calculation simulation.

Noise reduction of diesel engines installed in heavy duty vehicles is one of the highest priorities from the viewpoints of meeting the regulations for urban traffic noise abatement and noise reduction in the cabin for lightening fatigue with comfortable long driving. It is necessary that noise reduction measures then be applied to those causes. Noise reduction measures for the diesel engine can be classified into five categories on the noise radiation block-diagram. These are, reduction of combustion and mechanical forces, deformation and vibration control of cylinder block, vibration control of fastened components, prevention of standing wave and close fitting shields. All noise reduction measures for the diesel engine researched for the purpose of practical use are fully described in this paper.

The separation of combustion noise and mechanical noise from the total noise of a four-cylinder in-line diesel engine at idling was carried out with high accuracy by changing the fuel injection timing. The mechanical noise, which accounts for the major share at 93%, was then separated into noises from the typical mechanical causes, and the valve train was found to be the major noise source. From analysis of the noise generating mechanism for the valve train, it was clarified that the noise was caused mainly by the gear rattling owing to the variation in the camshaft drive torque.

Reducing friction between the piston ring and cylinder is an effective way of meeting the demand for lower fuel consumption in vehicle engines. To that effect, the authors have proposed a new and efficient friction reduction treatment for the cylinder. At first glance, this treatment seems similar to typical microtexture treatments, but it is built on a different approach. Through a rig tester, it was confirmed that optimizing the shape of the dimples and the treatment area for the cylinder improves FMEP between the piston ring and the cylinder liner by 17%. This report presents an analysis of the test results to explain the mechanism by which this effect is achieved. Fuel consumption was measured in an actual engine, and a maximum fuel consumption improvement of 3.2% was confirmed after conversion to the Japanese heavy duty vehicle fuel economy standards (Category T2). Lubricating oil consumption, blow-by and durability were also examined.

We have developed a new test method in which temperature of cavity lip of a piston alone during engine rotation is reproduced, cavity lip strain is measured. As the results of strain measurement using the test method in a condition that simulates of conventional engines, a strain behavior was out-of-phase. And in a condition that simulates of high-load engines in future, strain behavior was clockwise-diamond cycle. It was found from the result of the test method developed that strain increased on the cavity lip. The fatigue life of the cavity lip was evaluated using the strain measured and isothermal fatigue curves which obtained by the strain controlled isothermal fatigue test. The result of engine durability test has revealed that the developed method was valid for thermal fatigue evaluation of the cavity lip.

The change in the smoke emissions from a diesel engine with the shapes of the combustion chamber and the in-cylinder density was investigated with focuses on the mixing and the soot formation in a spray flame. First, the mixing of the fuel and air between the nozzle exit and the set-off length was used as an indicator for the formation of soot. Although this indicator can explain the influence of the density, it cannot explain the changes in the smoke emissions with a change in the shape of the combustion chamber. Next, by focusing on the soot distribution in a quasi-steady-state spray flame, the soot formed in the high-density condition of an optically accessible engine was investigated by applying two-color method. These results showed that the positional relationship between the maximum soot amount position and the flame impinging position can be a major influence on the smoke emissions.

Hino Motors developed J-series 4.7-liter inline-four cylinder and 7.7-liter inline-six cylinder engines for complying with the 2004 U.S. exhaust emissions regulations. Several technologies were incorporated in the development process to accomplish simultaneous reductions in both exhaust emissions and fuel consumption while the engine performance, reliability, and durability were maintained at the levels acceptable for truck application. Newly developed technologies include a cooled EGR system, a common-rail fuel injection system, a VNT system, and an engine control system for harmonized control of EGR valve and VNT. This paper reports the development approaches and results.

The coupling behavior of the torsional, bending, and longitudinal vibrations in the crankshaft is described. The incidental excitation forces under crankshaft torsional vibration due to reciprocating and rotating masses are derived theoretically. Experiments on the coupling behavior of the crankshaft vibrations and the excitation behavior in the engine structure were performed in a four-cylinder automotive engine; their results are discussed.

Recently, exhaust emission has been enforced on diesel engines for the countermeasure of environmental problems. Accordingly, the cylinder pressure in the engine is being increased to improve fuel efficiency, the engine bearings must be used under severe conditions of high specific load. Because the connecting rod bearings, particularly of diesel engines, are used at high specific loads that exceed 100 MPa, elastic deformation of the bearing surface occurs, and the oil film thickness decreases at the edges of the bearing length in the axial direction. This causes the bearings to contact with the crankshaft, thus resulting in the wear of the bearings, which could even result in seizure. The following factors contribute to seizure: bearing materials, bearing shapes, machining methods, and incorrect assembly. Focusing on these factors, this study evaluated the behaviors exhibited by connecting rod bearings in actual engines by using the rig testers.

A newly developed OHC (Over-Head Camshaft) prototype of a six-cylinder in-line diesel engine (with bore size: 114mm, stroke size: 130mm) was studied, comparing with the previous version of OHV (Over-Head Valve) type engine (with bore size: 110mm, stroke size: 130mm). It was found that the new type of cylinder block (with 130.8 kg of mass) has significantly lower natural frequencies than those for the previous type of cylinder block (with 133.2 kg of mass). Furthermore, slightly more predominant engine noise and vibration were induced in the new engine. The vibration behavior and the excitation force transmission characteristics were investigated by EMA (Experimental Modal Analysis). We performed a series of impact tests for (1) free-free cylinder block, (2) free-free crankshaft substructure with torsional damper and flywheel attached, and (3) the case where (1) and (2) are assembled together.

The objective of this study is to improve fuel economy and reduce carbon dioxide emissions in diesel-electric hybrid automotive powertrains by developing an exhaust gas turbine generator system which utilizes exhaust gas energy from the turbocharger waste gate. The design of the exhaust gas turbine generator was based on a conventional turbocharger for a direct-injection diesel engine. Data from steady-state bench tests using air indicates about 50% of the turbine input energy can be converted to electric energy. Turbine generator output averaged 3 kW, while a maximum of about 6 kW was observed. Based on this data, we estimate that energy consumption in a vehicle could be reduced between 5% and 10%. Engine tests were conducted under both steady-state and transient conditions. These tests revealed that optimal performance occurred under high-speed, high-load conditions, typical of highway or uphill driving, and that performance at low-speed, low-loads was relatively poor.

This paper describes the experimental studies of turbocharged and intercooled diesel engines with particular emphasis on combustion characteristics following increase of boost pressure. Through these studies, it has become possible to determine the optimum air quantity for minimizing fuel consumption at each engine speed range under the restrictive conditions of NOx emission, exhaust smoke and maximum cylinder pressure. Discussed also is the lack of air quantity in the low engine speed range of high-boost turbocharged diesel engines. Various turbocharging systems to improve air quantity in this speed range are introduced herein. Practically the engine performance of conventional turbocharging, waste gate control turbocharging and variable geometry turbocharging are discussed from the viewpoint of torque recovery in the low engine speed range.