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A flexible fuel vehicle (FFV) was evaluated through various tests for its potential as an alternative to the conventional gasoline vehicle. This paper presents the systems incorporated in the FFV and the test results. 50,000 mile emission durability tests were also performed and the potential of the FFV as a “Low Emission Vehicle” was assessed. As the result of extensive engineering work, we successfully developed a Galant FFV which exhibits very good durability and reliability. The emission control system which we have developed demonstrated that the vehicle has a good potential to comply with the California formaldehyde emission standard of 15 mg/mile. However, due to the large portion of unburnt methanol in the tail-pipe emissions, FFVs will have more difficulty than gasoline vehicles in meeting non-methane organic gas (NMOG) standards applicable to “Low Emission Vehicles”.

Protection of the Earth's environment by means of energy saving and cleaning up of air pollution on a global scale is one of the most important subjects in the world today. Because of this, the requirements for better fuel economy and cleaner exhaust emissions of internal combustion engines have been getting stronger, and, in particular, simultaneous reduction in nitrogen oxides (NOx) and particulate matter (PM) from heavy-duty diesel engines (HDDEs) without degrading fuel economy has become a major subject. Mitsubishi Motors Corporation (MM) has been selling diesel-powered heavy-duty trucks in the U.S. market since 1985 and has agressively carried out development work for meeting the 1991 model year exhaust emission standards.

A characteristic mechanism of in-cylinder combustion is “time-domain mixing” which mixes up unburned gas, products in the different stages of combustion process, and burned gas, by “eddy”, a flow component with its scales of several to 10 mm. It seems to play a role in completing the combustion. Now that direct injection is a central engine technology, a keyword to combustion control is “freedom of mixing”, that is, no restriction on mixture formation, realized by direct injection. Various kinds of combustion control technologies utilizing it, have been presented. After combustion control for a premixed leanburn gasoline engine, and a direct injection gasoline engine, was achieved by turbulence control, and mixing control, respectively, the next target of combustion control will be ignition control. It will be possible, by controlling some boundary condition on combustion and fuel chemistry. Time-domain mixing and freedom of mixing will support it.

In the heavy-duty commercial vehicle market in Japan, particularly in the segment of dump trucks and tractors, naturally aspirated engines maintain a dominant market share because of their superior torque characteristics in the low speed range. In order to meet the ever increasing needs for higher speeds of transportation, better fuel economy and higher reliability, and the needs for increasingly strict exhaust emission regulations, Mitsubishi Motors Corporation (MMC) has developed the 8M20, a 20 liter V8 diesel engine. The '92 model series of “THE GREAT”, MMC's main heavy-duty trucks, has featured this new and powerful engine and has been in the market place since October, 1991. The 8M20 is a naturally aspirated engine that provides an output of 294kW/2200rpm, complying with the current Japanese exhaust emission regulations.

Ammonia Selective Catalytic Reduction (SCR) is adapted for a variety of applications to control nitrogen oxides (NOx) in diesel engine exhaust. The most commonly used catalyst for SCR in established markets is Cu-Zeolite (CuZ) due to excellent NOx conversion and thermal durability. However, most applications in emerging markets and certain applications in established markets utilize vanadia SCR. The operating temperature is typically maintained below 550°C to avoid vanadium sublimation due to active regeneration of the diesel particulate filter (DPF), or some OEMs may eliminate the DPF because they can achieve particulate matter (PM) standard with engine tuning. Further improvement of vanadia SCR durability and NOx conversion at low exhaust gas temperatures will be required in consideration of future emission standards.

Ammonia Selective Catalytic Reduction (SCR) is a key emission control component utilized in diesel engine applications for NOx reduction. There are several types of SCR catalyst currently in the market: Cu-Zeolite, Fe-Zeolite and Vanadia. Diesel vehicle and engine manufacturers down select their production SCR catalyst primarily based on vehicle exhaust gas temperature operation, ammonia dosing strategy, fuel quality, packaging envelope and cost. For Vanadia SCR, the operating temperature is normally controlled below 550oC to avoid vanadium sublimation. In emerging markets, the Vanadia SCR is typically installed alone or downstream of the DOC with low exhaust gas temperature exposure. Vanadia SCR is also utilized in some European applications with passive DPF soot regeneration. However, further improvement of Vanadia SCR NOx conversion at low exhaust gas temperatures will be required to meet future emission regulations (i.e.: HDD Phase 2 GHG).

Honeycomb substrates are widely used to reduce harmful emissions from gasoline engines and are exposed to numerous thermal shocks during their lifetime making thermal shock resistance one of the key factors in designing honeycomb substrates. More stringent emission regulations will require the honeycomb substrates to be lighter in weight to improve light-off performance and to have better thermal shock resistance than conventional honeycomb substrates to handle higher expected temperature gradients. Thermal shock resistance is generally evaluated on a substrate by evaluating the thermal strain caused by temperature gradients inside the substrate during durability testing [1,2]. During the test, a heated substrate is cooled at a surface face to generate temperature gradients while the temperature inside the honeycomb substrate is monitored by multiple thermocouples.

To meet the increasingly strong demand for high-speed transportation, better fuel economy, higher reliability and the social requirements for more strict Japanese regulations against exhaust and noise emissions, Mitsubishi Motors Corporation has recently developed the 6D40T1 in-line 6-cylinder, 12.0-liter turbocharged and intercooled diesel engine for heavy-duty trucks. This engine meets the 1989 Japanese exhaust emission regulations and has an output of 258 kW. To achieve both fuel economy and good drivability, Mitsubishi's original, electronically-controlled fuel injection system was adopted. The so-called prestroke-controlled fuel injection pump is capable of flexible and precise control of both fuel injection rate and timing. The basic structure of the 6D40T1 was designed with high rigidity to permit high cylinder pressures. In addition, to reduce friction and heat losses, a 4-valve design, roller cam followers with needle roller bearings, and shortened exhaust ports were adopted.

Recent global environmental problems which have come to light must be solved for ensuring the survival of the human race. And it is of the utmost importance that we give to our descendants a world full of nature and beauty. In the past years Mitsubishi Motors Corporation (MMC) has long been positive in research and the development activities so as to satisfy the demands for low emission and good fuel economy vehicles. (1) As one example of our research efforts, the technology that will meet the US '94 HDDE exhaust emission regulations, which is one of the most stringent regulations in the world, is described in this paper. The exhaust emissions were reduced by improvement of combustion, using the pre-stroke control type fuel injection pump and optimizing the combustion chamber shape. Efforts were also made to improve the oil consumption, in order to reduce PM (Particulate Matter) emission.

In the diesel engine industry, the growing trends are toward wider use of electronically controlled high pressure fuel injection equipment to provide better engine performance, while conforming to the stringent exhaust emission standards. Although there have been some recent announcements of a diesel engine that applies an electronically controlled common rail type fuel injection system, there is little literature published about any attempt to reduce both exhaust emissions and noise and to improve engine performance by varying injection pressure and injection timing independently and introducing pilot injection in combination. This paper describes the details of a study made on the parameters associated with injection timing, injection pressure and pilot injection and the procedures for their optimization, with an electronically controlled common rail type fuel injection system installed in an in-line 6-cylinder 6.9 liter turbocharged and intercooled DI diesel engine.

In response to stringent particulate matter (PM) emission regulations worldwide, developments of diesel particulate filter (DPF) continue apace in addition to engine modification for PM reduction. Particularly with buses used in urban areas, reduction methods in black smoke emissions are being researched in addition to the efforts to satisfy the aforementioned PM regulations. The system described in this paper was developed for use mainly with buses in large urban concentrations. The system described in this paper mainly consists of both wall-flow monolith filters for filtration of PM emissions and electric heaters for regeneration. A key feature of this system is that exhaust gas is used for effective combustion of PM during regeneration. With conventional systems, airpumps have been used to feed air for PM combustion during regeneration. With the new system, however, the use of an air pump was discontinued due to durability and cost considerations.

Mitsubishi Motors Corporation (MMC) has developed a new V configured 8 cylinder turbocharged and intercooled diesel engine (8M22T1) for the heavy-duty truck market. The engine is one of the first in its class to feature a common rail fuel injection system. This advanced engine management system was selected to meet the challenges of ever tightening emission regulation, specifically in the areas of smoke and noise. The 8M22T1 embodies a number of design innovations which have resulted in significant improvements in performance, fuel economy, durability and reliability.

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.

This paper describes the design and operation of the multi-layered zirconia heated exhaust gas oxygen sensor having small-sized and sheet-shaped sensing element. This sensor uses an electrode modified with a rhodium catalyst and heater by means of the thick-film technique. This modification of an electrode's composition and construction affects the reaction on unburned components in exhaust gas as well as the sensor performance. By the addition of a rhodium catalyst, the zirconia exhaust gas oxygen sensor shows acute sensitivity and faster response properties in the transient state on emission component(NOx) generation, in such a way that these sensors show better emission control properties for reduction of NOx emission in current emission control systems. The addition of a rhodium catalyst reduces the green effect of sensor properties, and no significant change of emission control properties is observed after 50,000 equivalent miles using the engine dynamometer durability test.

The high-temperature durability of 85 mm tip diameter silicon nitride ceramic radial turbine rotors was evaluated with a hot gas spin test rig. The rotors withstood up to a turbine tip speed of 700 m/s at TIT of 1300°C under partially loaded conditions and 570 m/s at TIT of 1300°C under fully loaded conditions, respectively. The material of the rotors was a post-HIPed silicon nitride. The basic fatigue properties of the material were measured at high temperatures. In the hot gas spin test, the temperature and stress distributions at the turbine blade were calculated with a finite element method. The results of the hot-gas spin test are discussed by means of a failure prediction analysis on the basis of the Weibull statistics.

The accuracy of real-time A/F measurement at engine test benches has been improved with a modified equation to calculate A/F from exhaust gas composition. In addition to CO, CO2, total hydrocarbon (THC) and O2, the proposed equation includes NO and NO2 concentration as variables. In an attempt to improve the accuracy of the assumed constants in the equation, experiments have been conducted using automotive exhaust H2O and H2 analyzers. The accuracy of the proposed equation was proven through experiments and it was also found useful for precise evaluation of three-way catalyst or oxygen sensor characteristics.

In the next few years, the USA, EU, and Japan plan to introduce very stringent exhaust emissions regulations for heavy–duty diesel engines, in order to enhance the protection air quality. This builds upon the heavy–duty diesel engine exhaust emissions regulations already in effect. At the same time, improvement in fuel consumption of heavy–duty diesel engines will be very important for lowering vehicle operating costs, conserving fossil fuel resources, and reduction of CO2 (greenhouse gas) levels. This paper presents a detailed review of a quiescent combustion system for a heavy–duty diesel engine, which offers breakthrough performance in terms of the exhaust emissions – fuel consumption trade–off, compared with the more conventional swirl supported combustion system. This conclusion is supported by experimental results comparing quiescent and swirl supported versions of various combustion system configurations.

The present paper describes the results of a joint development program focussing on a system approach to meet the EURO IV emission standards for an upper class passenger car equipped with a newly developed high displacement gasoline engine. Based on the well known catalyst systems of recent V6- and V8-engines for the EURO III emission standards with a combination of close coupled catalysts and underfloor catalysts, the specific boundary conditions of an engine with an even larger engine displacement had to be considered. These boundary conditions consist of the space requirements in the engine compartment, the power/torque requirements and the cost requirements for the complete aftertreatment system. Theoretical studies and computer modeling showed essential improvements in catalyst performance by introducing thin wall substrates with low thermal inertia as well as high cell densities with increased geometric surface area.

Selective catalyst reduction (SCR) using cordierite honeycomb substrate is generally used as a DeNOx catalyst for diesel engines exhaust in both on-road and commercial off-highway vehicles to meet today’s worldwide emission regulations. Worldwide NOx emission regulations will become stricter, as represented by CARB2027 and EuroVII. Technologies which can achieve further lower NOx emissions are required. Recently, several technologies, like increased SCR catalyst loading amount on honeycomb substrates, and additional SCR catalyst volume in positions closer to the engine are being considered to achieve ultra-low NOx emissions. However, undesirable pressure drop increase and enlarging after treatment systems will be caused by adopting these technologies. Therefore, optimization of the material and honeycomb cell structure for SCR is inevitable to achieve ultra-low NOx emissions, while minimizing any system drawbacks.

Fleet average SULEV30 emissions over FTP-75 must be met under full implementation of US Tier 3/LEV III emission regulation in 2025. The majority of SULEV30 certified 2021 model year vehicles are equipped with ≤ 2L displacement engines and some models adopt hybrid powertrain systems. Pickup trucks account for > 20% of passenger vehicles in the US. They could represent a quick route to meet fleet average SULEV30 targets. The newest pickup truck models are typically ULEV50 or ULEV70 certified. To reach SULEV30 or lower emission category, total tailpipe emissions must be reduced by more than 40%. Improvement of cold start emission is essential because over 70% of regulated emission is emitted during the first 60 seconds of a drive cycle with current engine and aftertreatment technology. High porosity (HP) ceramic substrate is designed to reduce thermal mass and time required to reach three-way catalyst (TWC) active temperature compared to conventional ceramic substrates.