The Differences & Common Traits of Racecars and SportscarsFeb 2nd, 2023
Do you know about the GT4 race category?
GT4 is a race category competed by race-specific cars modified from a production model with a minimum number of changes. Taking the production sportscar GR Supra as the base car, modifications are made in line with the GT4 specification to create the “GR Supra GT4” race-specific car. What are the differences between these two GR Supra machines and what parts and components do they share in common? And, what is the meaning of the ≒ mark (about the same)?
Knowing the answers to these questions will help you understand the basic principles behind Toyota’s “car-making.”
The GR Supra is a road-legal production sportscar that can be used on public roads. However, from the development stage it has been designed and engineered with the intention of also making it capable of competing in full-fledged motor sport competitions, in other words capable of competing on a race circuit. The race standard it is designed for is the “GT4” category. As a GT4 race car, it is required to share the same basic parts as the production car it is based on.
For this reason, even though the GR Supra GT4 is a race-specific machine, its basic parts and components are the same as the GR Supra that anyone can drive on public roads. Said in another way, the GR Supra anyone can own and drive has inherently the same basic performance potential as a racecar.
*The base model for the GR Supra GT4 is the North American market model GR SupraBody
Designed from the development stage with the aim of full-fledged race participation. That’s why the basic body parts are the same.
A GT4 racecar must retain the same body form (shape and size) as its base production model, with virtually no changes permitted. The production model GR Supra is therefore designed from the initial development stage with race competition in mind.
For this reason, although there may be race-specific additions such as a rear wing and cooling ducts, the body has basically the same shape and size as the production model. Note, however, that there may be a slight difference in the body’s overall length due to the addition of aerodynamic parts such as a front splitter.
Also, for purposes of weight reduction and safety measures, the windows may be changed from glass to polycarbonate, and the fuel tank may be changed to fit FIA specifications.
A highly reliable engine covering both public road & race track use.
The fact is that the GR Supra and the GR Supra GT4 mount exactly the same engine, with the same mechanical components. This is because, from the beginning, the GR Supra mounts the B58 type 3-liter, in-line 6 cylinder, DOHC, twin-scroll turbocharged engine, known for its great reliability and performance to handle the harsh acceleration demanded in racing.
However, because of the GT4-specific ECU (engine electronic control unit), the engine is controlled in line with the regulation to achieve increased race competitiveness and controllability.
Exhaust system adopting specialized parts to fit demands of the race environment.
In order to attain high power output and accommodate higher exhaust temperatures, the exhaust system is changed fully to race-specific parts. However, the only externally visible difference is the change from the production model’s two exhaust pipes to a single pipe on the GR Supra GT4.
Also, although it can be seen from the lower part of the body that the GR Supra GT4 has a single exhaust pipe, since the passages for the exhaust on the underside of the chassis remain the same as on the production model, an empty space remains where the second pipe would have been.
In motor sports, an especially large load is put on the transmission, but because that was taken into consideration in the design of the production model’s transmission from the development stage, only a small modification was needed in the hardware of this component to handle the increased power output of the engine.
However, because the GT4 category regulation allows only 7 gears, a change in software control was all that was necessary to overcome that limitation.
Note, however, that the drive shaft was changed to a stronger race-specific type, and although the differential case is the same, the contents were changed to a mechanical LSD.
The suspension on the GR Supra GT4 is the same as the production model in both format and geometry(*).
However, in order to achieve the freedom of settings needed for racing, the shock absorbers and springs are changed to adjustable types to accommodate differences in machine height. And to achieve great control accuracy for the bushings, changes were made from rubber to pillow balls.
Also, the braking force was raised to race-specific level.
By sharing many basic parts with the production model GR Supra, we are able to offer the GR Supra GT4 as a race-specific model at a very reasonable price. This will surely make the GR Supra GT4 a racecar of choice for use in races around the world. And in turn, we will feed back the volumes of data and ideas gained from GR Supra GT4 race participation to contribute to the further evolution and advancement of performance in the next-generation production model sportscar.
All of this adds up to truly make the GR Supra and GR Supra GT4 cars that “Use the base of motor sports to contribute to the realizing the aim of “making ever-better cars.”