Diamante/Sigma (1990)

   

Luxury sedan spearheading 3-number* Tax Reform

　                 　* The 3-number refers to large passenger cars that exceed a certain limit in Japan

　Kokuhiro Shibuya

 

 

The development of the Diamante/Sigma began in 1985, five years before its launch. At the beginning of development, the main members of the team went to Germany and drove on the Autobahn with expected Japanese and European competitors. Through the 200 km/h driving, which could only be experienced on a test course in Japan, we all keenly felt that Japanese cars were weak, lacking in individuality, and far from having the image of a true luxury car. This led me to the idea of creating a design that is both robust and elegant. In other words, it should be equipped with high technology that leads to credibility, and have a restrained form that expresses this technology, yet has an unshakable presence. The message is an aura that makes people turn their heads toward the car.

With this in mind, we designers created “exterior, interior, and color design based on advanced technology,” and at the time of its launch, the catchphrase “soft depth” will be used to promote a sense of luxury.

 

――　Development starts with 5-number* car　
         * The 5-number refers to smaller passenger cars compared to the 3-number in Japan

This car was initially planned as a luxury 5-number sedan, and the first 1/4 models were created by our Design Department in Japan, MSI Design Studio in California (Mitsubishi’s satellite studio), and Mr. Aldo Sessano in Italy. I was in charge of the interior at this time and would later be in charge of the exterior.

<1/4 models by Design Department>

<1/4 models by California Design Studio>

The 1/4 models were subsequently converted to 1/1 models through a selection process, with three proposals made in Japan and one in the U.S., and the Japanese proposal B was finally selected.

――　The emergence of 3-number global luxury sedan project

Meanwhile, around this time, another project, the plan for a 3-number global luxury sedan, began, and once again the Mitsubishi Design Department, California Design Studio, and Aldo Sessano were working on a 1/1 model, but it was soon abandoned.

Although the 5-number car was expected to be chosen as Proposal B, it was decided to consider an additional proposal to ensure the best possible result. Akamine of the exterior group and I of the interior group were in charge of the new proposal. However, the design was not as appealing as Plan B, and the design was decided on as Proposal B. However, two years had already passed since the start of development. However, around this time, two years after the start of development, there was information that the tax system was about to be revised to drastically reduce the automobile tax for 3-number cars, and the executives were faced with the dilemma of whether to proceed as is or revise the plan to a 3-number car.

Under these circumstances, the development of a global luxury sedan resumed, and Akamine and I were put in charge of the project. Since the interior design I had been in charge of up to that point had been almost mapped out, I had another designer take my place, switched my mind to the exterior, and got down to serious work.

Being the first global luxury sedan from Mitsubishi, I was more enthusiastic than usual. My aim was based on the “high-quality driving image” provided by the high-performance engine, which is one of Mitsubishi’s strengths. The form that would represent this image was “First, create a solid stance based on the lower body, which has a sense of unity with the tires. Then, starting with the forward-leaning nose, a dynamic cabin, and ending with the clean “coda tronca” rear end, the “orthodox sedan” is created.

The sketch drawn with this goal in mind was adopted, and we were about to move on to the next phase of the model.　Just then, the tax reform was announced. Executives immediately merged the plans for a number 5 sedan and a world sedan, making it a 3-number global sedan. It was decided that the Diamante would be a sashless-door personal saloon mainly for the domestic market, and the Sigma would be an orthodox sedan with sash doors for the domestic and export markets. The base of these designs was a rendering of the aforementioned global sedan, with Akamine and I in charge of the Diamante, and Kobayashi and Okuma in charge of the Sigma.

――　Creating the Diamante Image

At this point, sketches of the Diamante were created for the new project. These sketches were drawn with the 3-number size, which was expected to grow rapidly in Japan in the future, in mind to create a comfortable size that was roomy but not too large, with Plan A having an elegant taste and Plan B having a solid image with a sense of density. Proposal B was selected.

 

However, this sketch was somewhat too sedan-like, so I drew an image sketch of a more personal, coupe-like form that would crawl on the ground and drive gracefully, and began work on the model.　

After the decision was made, the timing of the launch was critical, and a schedule was set to finalize the design by early March of the following year, even though only sketches were prepared for the car before Christmas 1988. The project group that planned the vehicle, the designers, and all departments including modelers and data staff in the design department worked in unison on this short-term development project. In particular, the project leader, Jiro Imura, understood the importance of design and provided multifaceted support by visiting our studio every day. Thanks to him, we were able to concentrate on the design.

 

 

 

――　Struggles in Realizing Image

The first model, however, still lacked the image of a personal saloon in a sedan-like appearance, and although it had a massive feel, it looked heavy. After repeated tuning sessions with modelers Yokoyama-san and Yasui-san, we finally reached the direction we were aiming for.

The rear-end treatment took many changes. At first, it was coda tronca, but it looked heavy, so we rounded it. However, this time, motion was not felt. Next, a ducktail was added, but this was removed because it was not homogeneous. However, as a result, the rear area became heavy again. Realizing that this was also a failure, we thought we should redo the ducktail and asked Mitsuhashi, the director if we could go back to the ducktail again, prepared to be scolded. Although he was furious with me under the tight schedule, I was able to go for the plan. Even though the schedule was tight, we could not go ahead with a design we were not satisfied with. In the end, the ducktail was carefully returned to a shape that flowed from the waistline, and although it was a modest expression within the limits of aerodynamically effective, we were able to create a sporty image while tightening the rear end.

 

 

The distinctive front grille, which Mr. Akamine was in charge of, was required to be divided into three sections from the engineering viewpoint. The reason for this was deformation after molding, but the appearance of the grille was greatly reduced due to the division. The distinctive front grille, which Akamine was in charge of, was required to be divided into three sections from the engineering viewpoint. The reason for this was deformation after molding, but the appearance of the grille would be greatly spoiled by the division. Together with chief designer Yokoyama, we defended the one-piece grille, saying, “This is the essential face of this car”. As a result, the grille was plated in all grades to ensure strength and a thin perimeter frame.

 

The headlamps were initially simple rectangular shapes, but this did not create a personal look, so they were rounded all over and transformed into two lamps on each side with different sizes. However, in addition to being narrower vertically to secure the frame of the grille, the rounded shape reduced the reflective area. Therefore, the engineers solved this problem by adding a lens inside the lamps.

We were also particular about the body color. While looking at the model, we thought that black would be good, but wanted to use an emotionally deep navy blue to convey a sense of intellectual luxury, so we asked our colorist to develop an additional color to “give a solid sense of luxury” in a world where metallic and mica paints were at the height of their popularity. He responded, “The development period is long, so I can’t say for sure that we will be ready for production in time,” but he was prepared to go through the trouble. Together with team member Matsubara, they repeatedly made samples and conducted color checks outdoors in the middle of summer. The physical properties and workability of the paint were also verified through the efforts of related departments, and the paint was realized on the verge of mass production.

Kobayashi and Okuma worked closely with us on the Sigma, a variant to be launched three months later. The Sigma was designed as a “sedan with a sense of prestige,” and was separated from the Diamante, a personal saloon. The cabin was designed with six lights to ensure comfort and a bright interior, and the front grille was made of acrylic for novelty. The rear taillights were made to extend the entire width of the car, creating an imposing image. The two months of development of the basic design that had been running like an arrow passed like a whirlwind, and the Diamante and Sigma were approved on March 7, as originally planned.

 

――　Final touches

After the basic design was approved, there was still a lot of work to be done to make it a luxury car. In particular, we spent a lot of time tuning the highlights of the body and repeatedly checked the model outdoors to make sure it was a satisfactory surface. The staff and I worked together to overcome many challenges, especially with Akamine, who had been with us since the beginning, and together we worked our brains out to the fullest. Overcoming many challenges in a short period, the project team members became increasingly motivated to bring this car together, which led to a product with no compromises.

When the design was almost finalized, famed actor Ken Takakura, who had a close relationship with Mitsubishi and a deep knowledge of cars, visited our design studio. He had seen the model in the process of development before, but at that time he had just finished filming in Los Angeles, so he drove his car to see us to switch his mind to cars. His first words upon seeing the model were, “That’s nice,” and “Look, I’ve got goosebumps!” stated with a smile, and his words strongly touched my heart.

In May 1990, after the tax reform, the Diamante was introduced to the market ahead of its competitors as a new 3-number luxury car and was fortunate enough to win the 1990-1991 Japan Car of the Year award.

 

Sept 2024

 

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High-quality interior targeting new values

 

 

Kazuhiro Takakuwa

 

――　Quest for high-quality luxury

I joined the interior design team for Diamante, led by Kokuhiro Shibuya, when the preliminary design study was completed. The team had developed the concept of “targeting niche users who are familiar with the authenticity” based on the concepts of “RISE = Rich, Intelligent, Sexy, Emotional” and “New Snob/snob yet attractive”. I agreed with this concept and thought that the interior of this car should aim for “high-quality luxury” and its mission would be to catch up with and overtake European competitors such as Mercedes-Benz and BMW.

The 6th-gen. Galant, which was under development at this time, had a unique and distinctive design that later became known as the “Individual 4-door“and the Diamante, its higher-end model, naturally felt the need to aim for a higher level of quality.

The 6th-gen. Galant, which was under development at this time, had a unique and distinctive design that later became known as the “Individual 4-door“and the Diamante, its higher-end model, naturally felt the need to aim for a higher level of quality. To do so, however, it was necessary to understand what “high-quality luxury” means, however, we, in-house designers, are far from the luxury lifestyle, and there were no first-class stores in the countryside of the Mikawa region where we work. So, the Product Planning Department at the Tokyo headquarters offered us the opportunity to experience luxury boutiques and high-end French restaurants in the Aoyama and Roppongi areas, and we spent a day in Tokyo wearing our finest clothes. Although it was a short time, it was like preparing for a role as an actor, so to speak, and we were able to get a reasonable idea of what is required in the world of the top class.

――　Interior that engages all five senses

Upon returning to Okazaki, the team freely discussed the direction of the design while the mood from the unusual and rich experience in Tokyo was still fresh in our minds. What we all agreed on was that while the exterior design of a high-quality product is mainly expressed through its form, in the case of interior design, it is necessary to express it not only through form, but also through the design of all the elements that people perceive with their five senses, including touch, sound, scent, and even furnishings (spatial presentation). With this image in mind, we moved on to the next stage of sketching.

――　From sketches to clay models

The four members of the team made various sketches and narrowed down the direction of the design, and my design was combined with the leader, Shibuya-san’s, as a single proposal, which was called “Surround interior” with a sense of continuity throughout the interior, centering on the T-shaped instrument panel that provides equal hospitality to the two front seat passengers. The other proposal was a driver-oriented sporty design.

After that, we made rough models of the two proposals out of foam and then proceeded to make clay models. Since this was my first experience in interior design, Shibuya-san did the overall planning, and I worked mainly on the design of the gauges, control levers, switches, etc. Usually, the models at this stage are made by outsourcing the wooden models, but Shibuya-san dared to choose clay models.

Clay models tend to be discouraged because they require more work by the in-house modelers, but I think this was an appropriate choice in pursuit of a high-quality feel because it was easier to study the varied and subtle shapes with clay models.

On this model, the most careful attention was paid to creating a cocoon-like interior with a smooth flow of soft padding from the instrument panel to the floor console and door trim. As a result, we were able to express a satisfactory quality at this stage, thanks to the skill of veteran modeler Noboru Sakamoto, who skillfully created the delicate modeling. At this time, I was deeply impressed by the importance of the modeler’s expressive ability in giving shape to the design.

――　Design direction

Halfway through the development, the plan was changed and the body was widened. The center console was thus widened, giving the instrument panel an imposing impression, and the overall image became more upscale. The instrument panel was highly evaluated at the subsequent design review meeting, and the design direction was easily approved. On the other hand, the exterior design did not receive the expected approval, and the project came to a standstill. However, Jiro Imura, the project director, said, “Why don’t we just use this image of the interior to create the exterior?” This led to an unusual turn of events, with the leader, Shibuya-san, taking charge of the new exterior design.

――　Intense interaction with engineers

After the design was directed, Shibuya-san decided to concentrate on the exterior for a while, but with the support of his replacement, the design process moved from here to the stage of refining and detailing for mass production, while communicating with the engineering department.

Natural continuity is the key to this“Surround Interior”. We worked with the engineering department to determine how to minimize the installation tolerances of the parts to the nearest tenth of a millimeter. In addition, we were upset when the engineers requested that the eaves on the top of the center console be cut off because the top surface of the eaves obstructed the downward airflow from the air vents. The eaves was an important feature of the instrument panel, and if it was removed, the design would be ruined. As a result of in-depth discussions, it was proven that the airflow we insisted on was valid, and we were able to keep the design.

The ergonomics was pursued together with the design by making the switches and control levers as blind-touch friendly as possible, while at the same time considering intuitive ease of operation. Thus, step by step, the enthusiasm of the designers and engineers brought us closer to our goal of a high-quality car.

 

――　Finishing touches for high-quality

The final stage of design development involved color and materials. The uniformity of texture and color of the various components that make up the “surround interior” with its sense of continuity is key to the taste of a luxury car.

First of all, slash molded soft padding was used not only for the instrument panel but also for the door trim. This was rare even for a luxury car, and the plan was to use a large flowing pattern to give a sense of continuity to the high-quality texture of the padding, and to express a craft-like softness as a whole.

We then looked for a large flowing leather texture, but could not find anything like it in the existing leather materials. We decided to make a new leather texture from scratch, and as a result of searching around for a base material, we consulted with an upholstery manufacturer where my senior at university was the head of the design department, and they cooperated with us, allowing us to use one of their treasured hides that they had found in Vienna, Austria. The leather was used to create a prototype seat, and the texture was confirmed. The final interior model was then created and approved using the leather.

The inside door handles were designed with a form that fits comfortably in the hand through a series of refinements, and the surface treatment was not the usual chrome plating, but a subdued color reminiscent of titanium, with a smooth feel to the touch with a low gloss. The wood grain panels on the instrument panel, floor console, and door trim were carefully tuned in terms of color, pattern, and texture to achieve a deep, high-quality feel. The analog clock in the center of the instrument panel has three hands to create a prestigious atmosphere.

 

The color of the switches and levers is dark warm gray, rather than the conventional black, and the letters and pictograms are light beige, rather than the conventional white, for a high-quality feel. The seat fabric is made of wool, which offers excellent comfort. Wool is a difficult material to meet automobile specifications, but with the cooperation of Suminoe Textile, we were able to overcome this difficulty.

 

 

The team worked hard to create a first-class interior space by giving every component a genuine sense of materiality and expression. This was based on the fact that we all shared the leader Shibuya-san’s sense of high-quality and that Imura, the project director, truly understood the importance of design in this car and generously spent a great deal of money on the design.

 

――　Looking back

The Diamante ultimately adopted Shibuya-san’s exterior design, which reflected his design philosophy both inside and outside the car. The same was true of the 6th-generation Galant, which was launched a step ahead of the Diamante, but this is a very rare case in corporate car design, and for that reason, I think a wonderful sense of unity was created in the design.

Despite the twists and turns in development, we were able to create a luxury car with a new sense of value unique to Mitsubishi. We were fortunate enough to be ahead of our competitors in taking advantage of the revised taxation system for domestic 3-number cars, and were rewarded with the Car of the Year award and the Good Design award. Our initial goal was to “catch up with and surpass European cars,” and I remember how happy we were to hear that not a few customers had switched from European cars after the launch. For me, it was a great fortune to be a part of this project, and at the same time, it was a valuable experience as a designer.

September 2024