Developing the GR Supra using a combination of “real” and “virtual”

On March 16, at the FIA GT Championships that took place in Paris, France, a talk show was held with Tetsuya Tada, Chief Engineer of GR Supra and project general manager of TOYOTA GAZOO Racing Company’s GR Management Division, and Kazunori Yamauchi, producer of the Gran Turismo series and president of Polyphony Digital Inc.

The relationship between Tada and Yamauchi can be traced back to the development of the Toyota 86, and of course continues to the development of the GR Supra. It might even be said that their relationship has enabled sports cars to be developed using a combination of “real” and “virtual.” During the talk show, Tada, Chief Engineer of GR Supra, discussed the technologies incorporated in the car; he also revealed his thoughts about the GR Supra GT Cup, a one-make race that will take place via the Gran Turismo Sport PS4® game.

1.55 ： 1

Yamauchi / Does anyone here know the meaning of 1.55:1?

Tada / 1.55:1 is the critical number that defines the performance of the GR Supra.

This number is the ratio between the car’s wheelbase (the distance between the centers of the front and rear wheels) and its axle track (the distance between the centers of two wheels on the same axle); for sports cars, there is a golden ratio between its wheelbase and axle track.

The majority of sports cars regarded as having good handling and being enjoyable to drive have a ratio of approximately 1.6:1. However, the GR Supra has wheelbase that is even shorter than 1.6—we intend to announce it as having a ratio of 1.55:1.

In Gran Turismo, it is possible to practice driving a racing kart—the GR Supra’s wheelbase-axle track ratio is close to that of a racing kart; its wheelbase is even shorter than that of the 86.

As you know, shortening the wheelbase enables incredibly quick turning, but at the risk of decreasing straight line stability. This is something I would like to discuss in further detail.

50 ： 50

Tada / There are many cars with a 50:50 front-rear weight distribution. Indeed, the top Gran Turismo drivers who have gathered here today control the weight distribution using accelerator and brake pedals to record super-laps.

For this reason, we took great care to ensure that the GR Supra possesses an accurate 50:50 weight distribution. When designing the structure of the car, it was no easy task to make the wheelbase extremely short and, at the same time, achieve a 50:50 front-rear weight distribution.

Of course, at the initial basic design stage, we designed the car to have a 50:50 balance. As development progressed, however, there was a tendency for more and more weight to shift to the front. One of the reasons for this is that, for a sports car, low weight is absolutely crucial.

When making a car as light as possible, it always happens that the rear of the car becomes lighter; there is, in fact, little scope to make the front lighter. As a result, after we had made great advances in development and even made preparations for mass production, about a year before the scheduled launch of the GR Supra we overhauled its design and made the engine about 52 millimeters lower than the initial design.

Yamauchi / Gran Turismo players will know that this can have an extremely negative impact on the car’s maneuverability—that one percent is extremely important.

Agillity＆Stability

Yamauchi / Agility and stability—why are you using these opposite ideas in the same sentence?

Tada / The GR Supra has a short wheelbase and, in principle, it turns extremely quickly—it has outstanding agility.
However, cars with such short wheelbases lack stability when traveling at high speeds in a straight line. This is why there are so few cars with a wheelbase-axle track ratio of less than 1.6:1.

Yamauchi / You adopted differential gears in order to exceed the limits, is that correct?

Tada / Yes, there is in fact a secret behind the differential gears.
As you all know, sports car differential gears utilize a limited-slip differential (LSD).
The GR Supra is equipped with a mechanism that enables the lock ratio to be freely adjusted between 0 and 100 percent.

Yamauchi / In other words, when you want to turn, you set the differential gear to free; and when you want to go in a straight line, or when you want to increase traction, you lock the differential gear.

Tada / Basically, that’s it. In addition—and this is something I think you have all experienced in the Lancer Evolution—the GR Supra is also capable of Active Yaw Control—that is, it can use the differential to generate yaw moment.

Yamauchi / In other words, the GR Supra’s differential gearing can be used for yaw control as well.

Body rigidity

Yamauchi / Next, I would like to talk about body rigidity. The GR Supra has an extremely rigid body. In actual fact, it is even more rigid that the carbon-bodied Lexus LFA. What were your reasons for this?

Tada / The GR Supra uses no carbon at all; it is made entirely of steel and aluminum.
The main reason for this is that, if we used carbon, the price of the car would increase, and this would mean that fewer people would have the chance to drive it. As to why the car is so rigid, despite not using carbon, the answer is extremely simple.
The GR Supra shares the same new platform design as the open-top BMW Z4. The underside—the flat bottom of the body you can see on this picture—is responsible for all the rigidity of the car, and we made sure it would perform appropriately; however, the GR Supra also has a roof, and the addition of the roof significantly increases the rigidity of the car.

Yamauchi / The car is also distinctive for its wide side sills—this is something you will all be able to see later if you open the car’s doors. But the side sills are a little unconventional.

Tada / The side sills refer to the width of the body when exiting from the seat. It is extremely difficult to enter and exit the vehicle.

Yamauchi / However, you don’t have to drive at a circuit to notice a car’s high body rigidity—differences in rigidity can be noticed just by turning at an intersection. It’s extremely important, isn’t it.

Tada / Yes, exactly.
In order to understand what makes the GR Supra unique, there is no need to drive fast. Even when going out to buy a cup of coffee—driving at that sort of speed—drivers should be able to fully experience how rigid the car body is.

“Tuning-ready”

Yamauchi / Finally, and most importantly—and this is something which will be of great interest to many people—there is the phrase: “tuning-ready.”

Tada / Even for the 86, we insisted all along that it was extremely easy to make tuning parts. We designed the 86 so that it would be easy to make cosmetic aero parts and exterior modifiers for it.
After that, as more and more people began to use the 86 for motorsports, we received large numbers of complaints—broken engines, for example, or broken differentials.
For this reason, we designed the GR Supra so that functional parts—the parts that affect its performance—could be easily tuned. As to how much you can increase the engine power—this depends on how well you can cool the engine, transmission, and differentials.
The GR Supra was designed with oil holes and drains, and with ample space to fit coolers, so that dedicated transmission and differential coolers could be attached.
I think racers and tuners will be surprised.

Yamauchi / In recent years, an increasing number of manufacturers have asked customers not to tune new cars but to drive them as they were purchased. To design a car on the assumption that it will be tuned is, for many of us, extremely refreshing.

Thoughts on the GR Supra GT Cup

Yamauchi / To finish, I would like to change the subject from the GR Supra to the GR Supra GT Cup. The GR Supra GT Cup will finally launch this year and, for you, I believe the GR Supra GT Cup is particularly meaningful.
Firstly, the GR Supra GT Cup is global competition. In other words, anyone can participate from anywhere in the world via the internet. There are 13 online races over the course of the season, and anyone can participate in them. The Grand Final will be held jointly with the World Tour at the Tokyo Motor Show.
You can all participate, so please give it all you’ve got!
Now, one of the goals of the GR Supra GT Cup is to find the world’s fastest Supra driver; but there is another goal, isn’t there?

Tada / We want people to drive the real GR Supra; but the GR Supra that features in the GR Supra GT Cup feels extremely similar to the actual vehicle, including the way it drives and its engine sound. Above all else, we want as many people as possible to drive it—that includes Gran Turismo fans and fans from around the world. However, while searching for the world’s fastest Supra driver, there is another important message we wish to communicate.

Since the GR Supra is a sports car, we intend to update the engine and chassis every year. Of course, we want you to update the GR Supra that features in the GR Supra GT Cup as well. We also want you to provide us with feedback from GR Supra GT Cup drivers—what they liked, what they were dissatisfied with, what they thought about the way it drives.

We intend to use these comments regarding the virtual GR Supra when updating the real GR Supra. We want GR Supra GT Cup drivers to become members of Team Supra, and participate in the development of the GR Supra. We look forward to everyone’s participation!

■ Kazunori Yamauchi
President of Polyphony Digital Inc.
Kazunori Yamauchi is the producer of the Gran Turismo series of real driving simulator games; more than 80.4 million games have been sold worldwide, as of May 5, 2018.

■ Tetsuya Tada
Project general manager of TOYOTA GAZOO Racing’s GR Management Division Tetsuya Tada is the Chief Engineer of GR Supra, and was also involved in the development of the Toyota 86, the GR series, and the GRMN series.