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Exhaust and evaporative emissions systems have been developed to match the characteristics and usage of the Toyota THS II plug-in hybrid electric vehicle (PHEV). Based on the commercially available Prius, the Toyota PHEV features an additional external charging function, which allows it to be driven as an electric vehicle (EV) in urban areas, and as an hybrid electric vehicle (HEV) in high-speed/high-load and long-distance driving situations. To reduce exhaust emissions, the conventional catalyst warm up control has been enhanced to achieve emissions performance that satisfies California's Super Ultra Low Emissions Vehicle (SULEV) standards in every state of battery charge. In addition, a heat insulating fuel vapor containment system (FVS) has been developed using a plastic fuel tank based on the assumption that such a system can reduce the diffusion of vapor inside the fuel tank and the release of fuel vapor in to the atmosphere to the maximum possible extent.

In recent years, catalyst systems such as a lean NOx trap (LNT) catalyst system and a urea selective catalytic reduction (SCR) system have been developed to obtain cleaner diesel emissions. At Nissan, we developed an emission control system for meeting Tier 2 Bin 5 requirements in 2003. On the basis of that technology, a new HC-NOx trap catalyst system has now been developed that complies with the SULEV standards without increasing the catalyst volume and precious metal loading. Compliance with the SULEV standards requires a further reduction of HC (NMHC) emissions by 84% and NOx by 60% compared with the emission performance Tier 2 Bin 5 compliant catalyst system. Consequently high conversion performance for both HCs and NOx is needed. An investigation of HC emission behavior under the FTP75 mode showed that a reduction of cold-phase HCs was critical for meeting the standard. Large quantities of HCs above C4 are emitted in the cold state.

In order to investigate the effect of sulfur and distillation properties on exhaust emissions, emission tests were carried out using a California Low Emission Vehicle (LEV) in accordance with the 1975 Federal Test Procedure ('75 FTP). To study the fuel effect on the exhaust emissions from different systems, these test results were compared with the results obtained from our previous studies using a 92MY vehicle for California Tier 1 standards and a 94MY vehicle for California TLEV standards. (1)(2) First, the sulfur effect on three regulated exhaust emissions (HC, CO and NOx) was studied. As fuel sulfur was changed from 30 to 300 ppm, the exhaust emissions from the LEV increased about 20% in NMHC, 17% in CO and 46% in NOx. To investigate the recovery of the sulfur effect, the test fuel was changed to 30 ppm sulfur after the 300 ppm sulfur tests. The emission level did not recover to that of the initial 30 ppm sulfur during three repeats of the FTP.

A new method for measuring unregulated substances in the exhaust gas is being investigated to clarify the influence of the vehicles' exhaust emissions into the environment. This paper explains our work on developing an analysis method for detecting and quantifying trace substances in the exhaust gas. A new analysis method was examined that uses thermal desorption to analyze trace amounts of polycyclic aromatic hydrocarbons (PAHs) in vehicle exhaust gas. This technique is faster than conventional methods and does not require any preconditioning of the samples before analysis. While lead and chloromethane were detected in the exhaust gas samples, it was made clear that these substances did not originate in the engine system. Accordingly, the results of this study indicate that careful attention must be paid to the test environment and the presence of measurement interfering substances in exhaust samples when measuring trace constituents in the exhaust gas from low-emission vehicles.

The original Toyota Hybrid System (THS) was installed in the Prius and was introduced in 1997 as the world's first mass-produced hybrid passenger car. Since then, THS has been continuously improved. In 2003 THS-II (marketed as Hybrid Synergy Drive [HSD]), was installed in a new larger Prius. In 2006 HSD was installed in a Rear Wheel Drive Vehicle: the LEXUS GS450h. This system achieved both 4.5-liter class power performance and compact class fuel economy with outstanding emissions performance. In 2007, this system is expanded to a mechanical all-wheel-drive(AWD) in the LEXUS LS600hL(with new V8 engine). This paper will explain this hybrid system which achieved both V12 class power performance and mid-size class fuel economy, while meeting the most stringent emission standard SULEV as a full-size vehicle.

The design of the newly developed Toyota AZ series 4 cylinder engine has been optimized through both simulations and experiments to improve heat transfer, cooling water flow, vibration noise and other characteristics. The AZ engine was developed to achieve good power performance and significantly reduced vibration noise. The new engine meets the LEV regulations due to the improved combustion and optimized exhaust gas flow. A major reduction in friction has resulted in a significant improvement in fuel economy compared with conventional models. It also pioneered a newly developed resin gear drive balance shaft.

The transfer efficiency for painting processes utilizing water-borne materials is low, and the residual paint is disposed of as waste. In this study, we focused on a recycling system to collect and dissolve the paint over-spray in the booth water, and to concentrate and regenerate it by means of an ultra filter (UF). Paint adaptable to the recycling system has been developed by providing compatibility between the high hydrophilicity of liquid paint and the high hydrophobicity of the paint film, in order to ensure the recyclability and the high anti-corrosion performance required of paint on automobile underbody parts. This recycling technology is used in an actual propeller shaft painting process and provides large waste reduction and a decrease in painting cost.

Toyota Hybrid System (THS), the powertrain that combines a gasoline engine and an electric motor was first introduced in December 1997. It became the first mass-produced hybrid passenger vehicle in the world, gaining a reputation as a highly innovative vehicle, and its cumulative worldwide sales have exceeded 120,000 units. In 2003, THS had a further evolution. The “new-generation Toyota Hybrid System (THS II)” would be introduced on the new Prius. This report shall explain “THS II”, which achieved drastic improvements in power performance and fuel economy, while securing the most stringent emission standard Advanced Technology Partial Zero Emission Vehicle (ATPZEV).

CARB (California Air Resources Board) has required the evaporative emissions to be restricted to 1/4th of the parameter stated in the 1995 regulations. Furthermore, hydrocarbons (hereafter, HC) from the fuel system must be reduced to near 0.0 grams, according to the PZEV (Partial Zero Emission Vehicle) regulations enforced from 2003. The wet film in intake ports and fuel leaking from the injector nozzles evaporate and diffuse while the car is parked, and consequently may cause HC to leak the air cleaner inlet. The air cleaner which prevents HC leakage from the air intake system is already in mass production. In the course of designing this product to be installed in a vehicle, the authors developed a method to estimate the amount of HC that reaches the air cleaner. Based on detailed investigation on HC distribution and the changes that occur during parking, the HC amount reaching the air cleaner was calculated by both the equation of diffusion and the equation of state.

Experimental investigations were conducted with a direct-injection diesel engine to improve exhaust emission, especially nitrogen oxide (NOx) and particulate matter (PM), without increasing fuel consumption. As a result of this work, a new combustion concept, called Modulated Kinetics (MK) combustion, has been developed that reduces NOx and smoke simultaneously through low-temperature combustion and premixed combustion, respectively. The characteristics of a new combustion concept were investigated using a single cylinder DI diesel engine and combustion photographs. The low compression ratio, EGR cooling and high injection pressure was applied with a multi-cylinder test engine to accomplish premixed combustion at high load region. Combustion chamber specifications have been optimized to avoid the increase of cold-start HC emissions due to a low compression ratio.

In preparation for compliance with California's SULEV standard and Euro STAGE 4 standard, which will take effect in 2002 and 2005, respectively, we have developed a laminated planar oxygen sensor. The developed sensor has the following characteristics: high thermal conductivity and superior dielectric characteristic, due to direct joining of the heater element alumina substrate and the sensor element zirconia electrolyte; low heat stress at temperature rise, due to optimized heater design; superior sensor protection from water droplets, and improved sensor response, due to optimized arrangement of intake holes in the sensor cover. With these characteristics, the developed oxygen sensor can be activated in 10 seconds after cold start. This report describes the technologies we used to develop the early-activation oxygen sensor.

Authors have developed an apparatus which measures the piston temperature using electromagnetic induction. The characteristics of this apparatus are as follows; 1 Applicable to 6 points per cylinder and all cylinders 2 Capable of measuring while the engine is running from start to 6000r/min full-load operation 3 Wide measuring range; from -30 to 400 °C 4 High accuracy; ±2.5 °C 5 Quick and easy setup 6 High durability This technology contributes to realizing the best balance of piston reliability and matching of combustion conditions. In this report, authors analyzed its influences upon piston temperature when the ignition timing,the oil/water temperature or the oil flow from piston jet were changed, respectively.

Experimental investigations were previously conducted with a direct-injection diesel engine with the aim of reducing exhaust emissions, especially nitrogen oxides (NOx) and particulate matter (PM). As a result of that work, a combustion concept, called Modulated Kinetics (MK) combustion, was developed that reduces NOx and smoke simultaneously through low-temperature combustion and premixed combustion to achieve a cleaner diesel engine. In subsequent work, it was found that applying a low compression ratio was effective in expanding the MK combustion region on the high-load side. The MK concept was then combined with an exhaust after-treatment system and applied to a test vehicle. The results indicated the attainment of ULEV emission levels, albeit in laboratory evaluations. In the present work, the combination of the MK combustion concept and certain fuel properties has been experimentally investigated with the aim of reducing exhaust emissions further.

Fuel dilution is one of the phenomena requiring attention in direct-injection engines. This study examined the factors contributing to increased fuel dilution in direct-injection and conventional multipoint injection gasoline engines, focusing in particular on fuel dilution in the oil pan. The results showed that fuel dilution is affected by fuel consumption, fuel properties and oil/cooling water temperatures in multipoint injection engines. In addition to these factors, fuel injection timing is another factor that increases fuel dilution in direct-injection engines.

This paper describes the third generation of the partial zero emission vehicle (P-ZEV) technology originally adopted on the Nissan Sentra CA sold in California. The 2000 Nissan Sentra CA became the world's first gasoline-fueled car to qualify for P-ZEV credits from the California Air Resources Board (CARB). The third-generation P-ZEV system has been substantially reduced in size and cost, compared with the Sentra CA system, enabling it to be used on high-volume models. This system complies with the P-ZEV requirements, including those for zero evaporative emissions and Onboard Diagnostics II (OBD-II). To achieve a more compact and lower-cost system, an ultra-thin-walled catalyst substrate, the world's first to attain a 1.8-mil wall thickness, has been adopted along with catalysts that display excellent low-temperature activity. As a result, low-temperature catalyst activity has been significantly improved.

This paper describes the emission reduction technologies applied to 4- and 6-cylinder engines used on Japanese market models certified as ultra-low emission vehicles (U-LEVs) in Japan. To qualify for this rigorous U-LEV certification, a vehicle must reduce hydrocarbon (HC) and nitrogen oxide (NOx) emissions by an additional 75% from the levels mandated by Japan's 2000 exhaust emission regulations. Nearly all Nissan Japanese models fitted with a gasoline engine, ranging from in-line 4-cylinder engines to V6 engines, have now been certified as U-LEVs. This has been accomplished by further improving the emission reduction technologies that were developed for the Sentra CA, which was launched in the U.S. market in 2000 as the world's first gasoline-fueled vehicle to qualify for Partial Zero Emission Vehicle (P-ZEV) credits from the California Air Resources Board. The specific new technologies involved are as follows.

The original Toyota Hybrid System (THS) was installed in the Prius and was introduced in 1997 as the world's first mass-produced hybrid passenger car. THS has been continuously improved. In 2003 THS-II (marketed as Hybrid Synergy Drive [HSD]), was installed in a new larger Prius. In 2005 HSD was installed in two SUVs: the RX400h and Highlander Hybrid. This system achieved both V8 engine power performance and compact class fuel economy with outstanding emissions performance. In 2006, the HSD line-up is expanded to front-engine rear-wheel (FR) drive in the Lexus GS450h. This paper will explain this hybrid system which achieves both 4.5-liter class power performance and compact class fuel economy, while meeting the most stringent emission standard SULEV.

With the aim of improving the air quality in large cities, the California Air Resources Board (CARB) has stipulated that non-methane organic gas (NMOG) composed of carbon numbers from C1 to C12 must be reduced for vehicle categories designated as Transitional Low Emission Vehicles (TLEVs), Low Emission Vehicles (LEVs), Ultra low Emission Vehicles (ULEVs), and Zero Emission Vehicles (ZEVs). Although considerable research work has been done on this issue to date, the entire picture is still not clear. Studies done by the authors have been aimed at providing a better understanding of the potential for reducing automotive tailpipe emissions by using several clean fuel candidates. The major questions of concern are the extent to which emissions of certain species can actually be reduced and what fuel can provide the best performance under a reduced NMOG condition.

Nissan has developed a non-methane organic gas (NMOG) emission measuring method based on California Air Resources Board (CARB) procedures.1) In addition, a system to analyze the chemical species present in the exhaust gases at Low Emission Vehicles (LEV) and Ultra Low Emission Vehicles (ULEV) levels has been created. It was found that when using an electrically heated catalyst (EHC) to achieve the low emissions for LEV and ULEV levels, the interference between exhaust HC species and the contamination of the analyzing system are a serious problem for the measurement of speciated emissions. The methyl tertiary butyl ether (MTBE) contained in reformulated gasoline can interfere with HC speciation in the Chromatogram, requiring that the automatically speciated results be checked by a trained operator. The low exhaust HC emissions of bags 2 and 3 in the Federal Test Procedure (FTP) are nearly equal to that of the background air utilized in the constant volume sampler (CVS) dilution.

The California Low-Emission Vehicle (LEV) standards mandate a reduction in non-methane organic gases (NMOG). With the aim of analyzing NMOG emissions, a comparison was made of the hydrocarbon species found in the exhaust gas when different types of catalyst systems and fuel specifications were used. NMOG emissions are usually measured by removing methane from the total hydrocarbon (THC) emissions and adding aldehyde and ketone emissions. The NMOG level found in this way is thus influenced by the rate of methane in THC emissions. Another important factor in the LEV standards is specific reactivity (SR), indicating the formation potential of ozone, which is one cause of photochemical smog. Specific reactivity is expressed by the amount of ozone generated per unit weight of NMOG emissions, and is affected by the respective proportion of hydrocarbon species in the total NMOG emissions.