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At the engine restart, when the temperature of the catalytic converter is low, additional fuel consumption would be required to warm up the catalyst for controlling exhaust emission.The aim of this study is to find a thermally optimal way to reduce fuel consumption for the catalyst warm up at the engine restart, by improving the thermal retention of the catalytic converter in the cool down process after the previous trip. To make analysis of the thermal flow around the catalytic converter, a 2-D thermal flow model was constructed using the thermal network method. This model simulates the following processes: 1) heat conduction between the substrate and the stainless steel case, 2) heat convection between the stainless steel case and the ambient air, 3) heat convection between the substrate and the gas inside the substrate, 4) heat generation due to chemical reactions.

In this study, we combined a diesel engine with the Toyota Hybrid System (THS). Utilizing the functions of the THS, reducing engine friction, lowering the compression ratio, and adopting a low pressure loop exhaust gas recirculation system (LPL-EGR) were examined to achieve both low fuel consumption and low nitrogen oxides (NOx) emissions over a wide operating range. After applying this system to a test vehicle it was verified that the fuel economy greatly surpassed that of a conventional diesel engine vehicle and that NOx emissions could be reduced below the value specified in the Euro 6 regulations without DeNOx catalysts.

The use of ceramic insulation to reduce engine heat loss and thus improve fuel economy was examined but found to be detrimental rather than advantageous. This paper analyzes the reasons and presents an alternative approach, namely minimizing the heat transfer area. Experiments were conducted to determine the effects of surface smoothness on BSFC, output torque, heat release rate and piston temperature. It was found that with a mirror-finished combustion chamber, heat loss is decreased and consequently engine output is raised, while fuel consumption is lowered. The percentage reduction in heat loss was ascertained by numerically simulating combustion and was confirmed by FEM analysis of piston thermal distribution.

The effects of high boiling point fuel additives on deposits were investigated in a commercial turbocharged direct injection gasoline engine. It is known that high boiling point substances have a negative effect on deposits. The distillation end points of blended fuels containing these additives may be approximately 15°C higher than the base fuel (end point: 175°C). Three additives with boiling points between 190 and 196°C were examined: 4-tert-Butyltoluene (TBT), N-Methyl Aniline (NMA), and 2-Methyl-1,5-pentanediamine (MPD). Aromatics and anilines, which may be added to gasoline to increase its octane number, might have a negative effect on deposits. TBT has a benzene ring. NMA has a benzene ring and an amino group. MPD, which has no benzene ring and two amino groups, was selected for comparison with the former two additives.

The effects of Hydrotreated vegetable oil (HVO) on combustion and emission characteristics in a diesel engine were investigated by using spray analyzer, engine dynamometer and vehicle tests. Spray analysis showed that spray characteristics was virtually the same for HVO and diesel. From the results of the engine dynamometer and the vehicle tests, it was found that the high cetane number and the zero aromatics of HVO could reduce in HC and PM emissions. Moreover, as a result of optimized engine calcification, HVO is capable of improving partial fuel consumption and full-load torque. These results indicate that HVO has beneficial fuel characteristics for diesel engine.

Fuel efficiency improvement measures are focusing on both cold and hot conditions to help reduce CO2 emissions. Recent technological trends for improving fuel economy such as hybrid vehicles (HVs), engine start and stop systems, and variable valve systems feature expanded use of low-temperature engine operation regions. Under cold conditions (oil temperature: approximately 30°C), fuel consumption is roughly 20% greater than under hot conditions (80°C). The main cause of the increased friction under cold conditions is increased oil viscosity. This research used the motoring slipping method to measure the effect of an improved crankshaft bearing, which accounts for a high proportion of friction under cold conditions. First, the effect of clearance was investigated. Although increasing the clearance helped to decrease friction due to the oil wedge effect, greater oil leakage reduced the oil film temperature increase generated by the friction.

A new compact five-speed automatic transmission (A650E) has been developed for front engine rear wheel drive cars. The development of this transmission has been aimed at improving fuel consumption, power performance, engine noise reduction during highway cruising and smooth acceleration by employing a wide range of gearing and close gear ratios. Generally a five-speed automatic transmission is larger than a four-speed, because of additional friction elements and gears. This can result in a change in the floor panel of the car body. However, by removing a one-way clutch for second gear and employing a unique gear-train layout, this transmission has the same circumference and length as the conventional four-speed automatic transmission (A340E)(1).1 In order to reduce first or second gear noise, gear specification and supporting structures of planetary gears have been optimized by FEM analysis.

Toyota has been evolving a hybrid system since introducing the first mass-production hybrid vehicle in 1997 in response to the increasing automotive-related issues of CO2 emissions, energy security, and urban air pollution. This paper describes a newly developed hybrid system design and its performance. This system was developed with the main purpose to improve fuel consumption, especially for better real world fuel consumption; and to enhance its compatibility with multiple vehicle adoption by downsizing and reducing the weight of its components. At the same time, the hybrid system achieved improved power performance while satisfying stringent emission regulations in the world.

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. In the impact on exhaust emissions, the impact of high biodiesel blends into diesel fuel on diesel emissions was evaluated. The wide variety of biodiesel blendstock, which included not only some kinds of fatty acid methyl esters(FAME) but also hydrofined biodiesel(HBD) and Fischer-Tropsch diesel fuel(FTD), were selected to evaluate. The main blend level evaluated was 5, 10 and 20% and the higher blend level over 20% was also evaluated in some tests. The main advanced technologies for exhaust aftertreatment systems were diesel particulate filter(DPF), Urea selective catalytic reduction (Urea-SCR) and the combination of DPF and NOx storage reduction catalyst(NSR).

Environmental improvement is moving forward, due in part to the reduction of fuel consumption of automatic transmission(AT) vehicles as a result of social requirements in recent years and many measures have been implemented. Adoption of idling stop is a typical example introduced to reduce energy consumption while the vehicle is stopped to improve the urban environment. However, there are problems such as responsiveness and smoothness for an AT vehicle when the engine is stopped with the shift selector in “D” range. To overcome these problems, a new start clutch control system has been developed using an electric oil pump installed in a simple hybrid vehicle called a mild hybrid. As a result, a smooth feeling starting performance is achieved by operating the system in combination with the engine and other systems.

For the first time ever, a new hybrid system using a 42-V power supply system has been developed for better fuel economy, lower emissions and urban environment. This paper introduces the system configuration, features and gives actual vehicle evaluation results. This system has a motor generator (hereinafter abbreviated as M/G) connected to the engine crankshaft via a belt, in place of the alternator on a conventional vehicle. The electronic control of the M/G has five functions, 1 restarting the stopped engine, 2 driving the vehicle when starting, 3 driving auxiliaries when the engine is stopped, 4 power generation during ordinary traveling and 5 regenerative braking on deceleration braking. By restarting the engine via a belt with motor driving control, a smooth starting without discomfort is achieved. Furthermore, using this motor to drive auxiliaries during idle increases the number of idle stop opportunities.

In the present social environment, automobile demands further reduction of fuel consumption and light weight. Now that the reduction of vehicle weight is being pursued, even a slight looseness in each element of an automobile may become a source of vibration and noise due to the lowered rigidity of such an automobile. The quietness of vehicles is urged, spline backlash in the spline mechanism exhibits a problem in some cases. A propeller shaft, a part of the automobile driving system, also has a sliding spline mechanism as shown in Fig. 1. Such a propeller shaft is required to have functions of transmitting high torque driving forces, and absorbing the variation of the vehicle driveline overall length at the same time. Vibration and noise are apt to occur if when torque is applied, there is a significant balance fluctuation or great sliding resistance due to spline backlash.

Vehicles have been more required to save energy against the background of the tendency of ecology. As the result of improving efficiency of internal combustion engines and adoption of electric power train, heat loss from engine coolant, which is used to heat the cabin, decreases and consequently additional energy may be consumed to maintain thermal comfort in the passenger compartment in winter. This paper is concerned with the humidity control system that realizes reduction of ventilation heat loss by controlling recirculation rate of the HVAC system by using highly accurate humidity sensor to evaluate risk of fogging on the windshield. As the results of the control, fuel consumption of hybrid vehicles decreases and maximum range of electric vehicles increases.

In order to adapt to energy security and the changes of global-scale environment, further improvement of fuel economy and adaptation to each country’s severer exhaust gas emission regulation are required in an automotive engine. To achieve higher power performance with lower fuel consumption, the engine’s basic internal design such as an engine block and cylinder head were changed and the combustion speed was dramatically increased. Consequently, stroke-bore ratio and valve layout were optimized. Also, both flow coefficient and intake tumble ratio port were improved by adopting a laser cladded valve seat. In addition, several new technologies were adopted. The Atkinson cycle using a new Electrical VVT (Variable Valve Timing) and new combustion technology adopting new multi-hole type Direct fuel Injector (DI) improved engine power and fuel economy and reduced exhaust emissions.

Achieving the speed and performance of a true supercar was merely the starting point of this development. In addition, the development also focused on achieving emotive performance attributes to enhance driver appeal. For this the engine was developed to assist a vehicle handling provides unsurpassed response, the creating a feeling of infinite acceleration potential, response is instantaneous and based on close understanding of driver's reactions and Awe inspiring sound is providing. It meets the latest emission standard Euro V and achieves good fuel consumption with a wide range stoechiometric air fuel ratio, till speeds up to 240km/h.

A bench engine test for evaluating the fuel efficiency of automotive crankcase oils using modern engines was developed. The fuel consumption was primarily proportional to the viscosity of the oils down to 5 mm2/s at operating temperatures, indicating that the use of low-viscosity oil was effective in improving fuel efficiency. This may be because the oil film would be formed easily, since sliding parts, such as valve train systems, in modern engines are finely finished. Organo molybdenum dithiocarbamates were effective in improving fuel efficiency at high temperature. A 2.7% improvement in fuel efficiency relative to conventional SAE 10W-30 oils was achieved by the combination of low-viscosity SAE 5W-20 oils and organo molybdenum dithiocarbamates under constant operating conditions with engine speed 1,500 rpm and torque 37.2 N•m.

To meet the requirements for higher horsepower and torque as well as lower fuel consumption and emissions, we have developed a new “Intelligent Variable Valve Timing (VV-i)” system. It gives continuously variable intake cam phasing by up to 60 degrees crank angle (CA) . This system not only increases WOT output by optimizing intake valve closing timing but also reduces fuel consumption and NOx/ HC emissions under part load by increasing intake and exhaust valve overlap on 4 stroke Spark Ignited engines. VVT-i has been applied to optimize a new 3-liter inline 6 engine for higher torque and at the same time better fuel economy with continuous and wide-range cam phasing.

In order to meet requirements for lower fuel consumption, we have developed a technique for significantly decreasing valve train friction for a direct acting OHC engine. Droplets of pure titanium generated by the titanium nitride coating process of the shims improves the surface roughness of the cams, which eliminates the need to polish the cams. In an engine with these shims, the surface roughness of the cams is considerably improved within a few minutes of initial operation by the polishing action of the droplets. Valve train friction is greatly reduced by improving the surface roughness of the cams and shims, which results in better fuel economy.

The effects of multiple-injection on exhaust emissions and performance in a small HSDI (High Speed Direct Injection) Diesel engine were examined. The causes for the improvement were investigated using both in-cylinder observation and three-dimensional numerical analysis methods. It is possible to increase the maximum torque, which is limited by the exhaust smoke number, while decreasing the combustion noise under low speed and full load conditions by advancing the timing of the pilot injection. Dividing this early-timed pilot injection into two with a small fuel amount is effective for further decreasing the noise while suppressing the increase in HC emission and fuel consumption. This is realized by the reduced amount of adhered fuel to the cylinder wall. At light loads, the amount of pilot injection fuel must be reduced, and the injection must be timed just prior to the main injection in order to suppress a possible increase in smoke and HC.

Due to increasing demands for further CO2 reduction and tighter exhaust emissions regulations, automakers are increasingly downsizing turbo-charged diesel engines by raising specific power, or adopting low-pressure loop exhaust gas recirculation (LPL-EGR) systems to improve the EGR rate. However, adopting a higher boost pressure to increase the specific power, or introducing hot exhaust gas before the turbocharger compressor with the LPL-EGR system creates higher gas temperatures in the compressor, which results in soot-containing deposits derived from the engine oil in the compressor. This phenomenon causes significant deterioration of turbocharger efficiency. Therefore, countermeasures such as restricting boost pressure or limiting EGR usage in the operational map are necessary to prevent engine performance deterioration. Increasing the gas temperature in the compressor while preventing deposit formation should enable further improvements in fuel consumption and engine power.