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Mo-free 1.6-GPa bolt was developed for a Variable Compression Turbo (VC-Turbo) engine, which is environment friendly and improves fuel efficiency and output. Mo contributes to the improvement of delayed fracture resistance; therefore, the main objective is to achieve both high strength and delayed fracture resistance. Therefore, Si is added to the developed steel to achieve high strength and delayed fracture resistance. The delayed fracture tests were performed employing the Hc/He method. Hc is the limit of the diffusible hydrogen content without causing a delayed fracture under tightening, and He is the diffusible hydrogen content entering under a hydrogen-charging condition equivalent to the actual environment. The delayed fracture resistance is compared between the developed steel and the SCM440 utilized for 1.2-GPa class bolt as a representative of the current high-strength bolts.

To improve the fuel economy, we developed a turbo-charged spark ignition engine combined with a low pressure loop EGR system. A negative pressure control valve has been applied to achieve high EGR ratio in wide engine operation condition. In this paper, a new developed model-based control system for low pressure loop EGR with a negative pressure control valve will be described.

A gasoline particulate filter (GPF) is installed in a passenger vehicle for new exhaust regulation. However, ash in gasoline engine oil has a risk of clogging as well as performance decrease in the GPF. Therefore, new gasoline engine oil whose ash contents decrease to 0.8 mass% was developed in order to avoid the GPF clogging. In addition to this, our developed oil improves fuel efficiency (+0.2% from our SN 0W-16 fuel eco type oil) as well as anti-wear performance for gasoline engine, which resulted in meeting API SP/ILSAC GF-6 0W-16 official certification.

Contribution to carbon neutrality is one of the most important challenges for the automotive industry. As CO2 emission has been reduced through electrification such as hybrid electric vehicle (HEV) and plug-in hybrid electric vehicle (PHEV), internal combustion engines (ICEs) equipped in those powertrain systems are still necessary for the foreseeable future, and continuous efforts to improve fuel efficiency are demanded. To improve powertrain thermal efficiency, direct-injection turbocharged gasoline engines have been widely utilized in recent years. Super lean-burn combustion engine has been researched as a next generation of turbocharged gasoline engines. Further utilization of turbochargers is expected. Compared with turbocharged downsized gasoline engines available in the current market, much higher boost pressure must be utilized to realize the super lean-burn engines. As a result, compressor housing temperature will be very high compared with the current market one.

Nissan’s variable compression turbo (VC-Turbo) engine has a multilink mechanism that continuously adjusts the top and bottom dead centers of the piston to change the compression ratio and achieve both fuel economy and high power performance. Increasing the exhaust gas recirculation (EGR) rate is an effective way to further reduce the fuel consumption, although this increases the exhaust gas condensation in the cylinder bores, causing a more corrosive environment. When the EGR rate is increased in a VC-Turbo engine, the combined effect of piston sliding and exhaust gas condensation at the top dead center accelerates the corrosive wear of the thermal spray coating. Stainless steel coating is used to improve the corrosion resistance, but the adhesion strength between the coating and the cylinder bores is reduced.

Premixed charge compression ignition (PCCI) combustion is effective in reducing harmful exhaust gas and improving the fuel consumption of diesel engines [1]. However, PCCI combustion has a problem of exhibiting lower combustion stability than diffusive combustion [2, 3], which makes it challenging to apply to mass production engines. Its low combustion stability problem can be overcome by implementing complicated injection control strategies that account for variations in environmental and engine operating conditions as well as transient engine conditions, such as turbocharging delay, exhaust gas recirculation (EGR) delay, and intake air temperature delay. Although there is an example where the combustion mode is switched according to the intake O2 fraction [4], it requires a significant number of engineering-hours to calibrate multiple combustion modes. And besides, such switching combustion modes tends to have a risk of discontinuous combustion noise and torque.

Engine oil with viscosity lower than 0W-16 has been needed for improving fuel efficiency in the Japanese market. However, lower viscosity oil generally has negative aspects with regard to oil consumption and anti-wear performance. The technical challenges are to reduce viscosity while keeping anti-wear performance and volatility level the same as 0W-20 oil. They have been solved in developing a new engine oil by focusing on the molybdenum dithiocarbamate friction modifier and base oil properties. This paper describes the new oil that supports good fuel efficiency while reliably maintaining other necessary performance attributes.

It is well understood that using lower viscosity engine oils can greatly improve fuel economy [1, 2, 3, 4]. However, it has been impossible to evaluate ultra-low viscosity engine oils (SAE 0W-12 and below) utilizing existing fuel economy test methods. As such, there is no specification for ultra-low viscosity gasoline engine oils [5]. We therefore developed firing and motored fuel economy test methods for ultra-low viscosity oils using engines from Japanese automakers [6, 7, 8]. This was done under the auspices of the JASO Next Generation Engine Oil Task Force (“TF” below), which consists mainly of Japanese automakers and entities working in the petroleum industry. Moreover, the TF used these test methods to develop the JASO GLV-1 specification for next-generation ultra-low viscosity automotive gasoline engine oils such as SAE 0W-8 and 0W-12. In developing the JASO GLV-1 specification, Japanese fuel economy tests and the ILSAC engine tests for evaluating engine reliability were used.

The octane appetite of an engine is frequently characterised by the so-called K value. It is usually assumed that K is dependent only on the thermodynamic conditions in the engine when knock occurs. In this work we test this hypothesis: further analysis was conducted on experimental results from SAE 2019-01-0035 in which a matrix of fuels was tested in a single cylinder engine. The fuels consisted of a relatively small number of components, thereby simplifying the analysis of the chemical kinetic proprieties. Through dividing the original fuel matrix into subsets, it was possible to explore the variation of K value with fuel properties. It was found that K value tends to increase slightly with RON. The explanation for this finding is that higher RON leads to advanced ignition timing (i.e. closer to MBT conditions) and advanced ignition timing results in faster combustion because of the higher pressures and temperatures reached in the thermodynamic trajectory.

Dilution combustion with exhaust gas recirculation (EGR) has been applied for the improvement of thermal efficiency. In order to stabilize the high diluted combustion, it is important to form an appropriate turbulence in the combustion cylinder. Turbulent intensity needs to be strengthened to increase the combustion speed, while too strong turbulence causes ignition instability. In this study, the factor of combustion instability under high diluted conditions was analyzed by using single cylinder engine test, optical engine test and 3D CFD simulation. Finally, methodology of in-cylinder flow design is attempted to build without any function by taking into account the representative scales of turbulence and premixed combustion.

In recent years, boosted and downsized engines have gained much attention as a promising technology to improve fuel economy; however, knocking is a common issue of such engines that requires attention. To understand the knocking phenomenon under downsized and boosted engine conditions deeply, fuels with different Research Octane Number (RON) and Motor Octane Number (MON) were prepared, and the knocking performances of these fuels were evaluated using a single cylinder engine, operated under a variety of conditions. Experimental results showed that the knocking performance at boosted conditions depend on both RON and MON. While higher RON showed better anti-knocking performance, lower MON showed better anti-knocking performance. Furthermore, the tendency for a reduced MON to be beneficial became stronger at lower engine speeds and higher boost pressures, in agreement with previously published modelling work.

This report describes the implementation of the spark channel short circuit and blow-out submodels, which were described in the previous report, into a spark ignition model. The spark channel which is modeled by a particle series is elongated by moving individual spark particles along local gas flows. The equation of the spark channel resistance developed by Kim et al. is modified in order to describe the behavior of the current and the voltage in high flow velocity conditions and implemented into the electrical circuit model of the electrical inductive system of the spark plug. Input parameters of the circuit model are the following: initial discharge energy, inductance, internal resistance and capacitance of the spark plug, and the spark channel length obtained by the spark channel model. The instantaneous discharge current and the voltage are obtained as outputs of the circuit model.

The use of exhaust gas recirculation (EGR) in spark ignition engines has been shown to have a number of beneficial effects under specific operating conditions. These include reducing pumping work under part load conditions, reducing NOx emissions and heat losses by lowering peak combustion temperatures, and by reducing the tendency for engine knock (caused by end-gas autoignition) under certain operating regimes. In this study, the effects of EGR addition on knocking combustion are investigated through a combined experimental and modeling approach. The problem is investigated by considering the effects of individual EGR constituents, such as CO2, N2, and H2O, on knock, both individually and combined, and with and without traces species, such as unburned hydrocarbons and NOx. The effects of engine compression ratio and fuel composition on the effectiveness of knock suppression with EGR addition were also investigated.

An electric vehicle (EV) has less powertrain energy loss than an internal combustion engine vehicle (ICE), so its aerodynamic accounts have a larger portion of drag contribution of the total energy loss. This means that EV aerodynamic performance has a larger impact on the all-electric range (AER). Therefore, the target set for the aerodynamics development for a new EV hatchback was to improving AER for the customer’s benefit. To achieve lower aerodynamic drag than the previous model’s good aerodynamic performance, an ideal airflow wake structure was initially defined for the new EV hatchback that has a flat underbody with no exhaust system. Several important parameters were specified and proper numerical values for the ideal airflow were defined for them. As a result, the new EV hatchback achieves a 4% reduction in drag coefficient (CD) from the previous model.

During the last decade, fuel economy mandates (CAFE regulations) have driven engine downsizing and down-speeding trends. More recently, downsized turbos are percolating down to heavier SUVs and trucks. Larger/heavier vehicles require high torque engines to provide attractive dynamic performance. While higher torque requirements can be satisfied with new innovations like the variable compression engine, larger and more upscale vehicles also need to deliver higher quietness requirements. For this, the vibration control system for combustion induced forces with high torque engines become very important. To address both dynamic performance and quietness requirements, active engine mounts have been previously adopted, however challenges for light-weighting, downsizing, and costs have still persisted.

A new 2L gasoline turbo engine, named KR20DDET was developed with the world’s first mass-producible variable compression turbo (VC-Turbo) technology using a multi-link variable compression ratio (VCR) mechanism. It is well known that increasing the compression ratio improves gasoline engine thermal efficiency. However, there has always been a compromise for engine designers because of the trade-off between increasing the compression ratio and knocking. At Nissan we have been working on VCR technology for more than 20 years and have now successfully applied this technology to a mass production engine. This technology uses a multi-link mechanism to change the top and bottom dead center positions, thereby allowing the compression ratio to be continuously changed. The VC-Turbo engine with this technology can vary the compression ratio from 14:1 for obtaining high thermal efficiency to 8:1 for delivering high torque by taking advantage of the strong synergy with turbocharging.

For the launch of the redesigned Lexus LS, a new 3.5 L V6 twin turbo engine has been developed aiming at unparalleled performance on four axes, “driving pleasure”, “power-performance”, “quietness” and “fuel economy”. To achieve outstanding power-performance and high thermal efficiency, the specifications have been optimized for high speed combustion. The maximum torque of 600 Nm, power of 310 kW (yielding specific power of 90 kW/L), and the maximum thermal efficiency of 37% have been achieved using several new technologies including a high efficiency turbocharger. A prototype vehicle equipped with this engine and Direct-Shift 10AT achieved a 0-60 mph acceleration time of 4.6 sec, with extremely good CAFE combined fuel economy of 23 mpg and power-performance aligned with V8 turbocharged offerings from competing OEM’s.

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.

In emerging markets, Port Fuel Injection (PFI) technology retains a higher market share than Gasoline Direct Injection (GDI) technology. In these markets fuel quality remains a concern even despite an overall improvement in quality. Typical PFI engines are sensitive to fuel quality regardless of brand, engine architecture, or cylinder configuration. One of the well-known impacts of fuel quality on PFI engines is the formation of Intake Valve Deposits (IVD). These deposits steadily accumulate over time and can lead to a deterioration of engine performance. IVD formation mechanisms have been characterized in previous studies. However, no test is available on a state-of-the-art engine to study the impact of fuel components on IVD formation. Therefore, a proprietary engine test was developed to test several chemistries. Sixteen fuel blends were tested. The deposit formation mechanism has been studied and analysed.

The purpose of this work was to gain a fundamental understanding of which fuel property parameters are responsible for particulate emission characteristics, associated with key intermediate behavior in the engine cylinder such as the fuel film and insufficient mixing. Accordingly, engine tests were carried out using various fuels having different volatility and chemical compositions under different coolant temperature conditions. In addition, a fundamental spray and film visualization analysis was also conducted using a constant volume vessel, assuming the engine test conditions. As for the physical effects, the test results showed that a low volatility fuel displayed high particulate number (PN) emissions when the injection timing was advanced. The fundamental test clearly showed that the amount of fuel film on the impingement plate increased under such operating conditions with a low volatility fuel.