Regulations on the JGTC

Engine
The engine can be charged if it is the same make production engine. The position and installation of the engine are free in the engine as long as the original location and orientation are retained. The engines of most cars are installed so as to sit as low as possible, and as near to the center of the car as possible. Turbochargers may be fitted or removed.

Air Restrictors
Cars must be fitted with air restrictors, which are devices to control the intake air for the engine to maintain equal performance among the competitors. However, a well-tuned engine still has an output of a full 500 or 300hp.

Brakes
The type of braking system used is not regulated. However, anti-lock braking system are not allowed to be used.

Tires
Maximum width (complete wheel)
· GT500 : 14” (359mm)
· GT300 : 12” (305mm)
Maximum diameter (compete wheel)
· GT500 : 28” (711mm)
· GT300 : 28” (711mm)

Suspension
One of the keys to the supremacy of speed in JGTC is a car’s suspension. The only regulation here is that the car’s original suspension configuration is to be used.

Bodywork and Aerodynamic
Any modifications to the bodywork must resemble the original panels as nearly as possible. The engine hood, trunk lid and car doors may be replaced by parts made of fiber-reinforced plastic or lightweight alloys. The width of the bodywork across the front and rear wheel arches can be increased by 5cm on each side. Front spoilers and rear wings are permitted. There are no restrictions regarding the materials to be used for making the spoiler or rear wing, but sizes for these components are controlled. The use of rear diffuser can be used as well.

Drivers
As JGTC is comprised of semi-endurance races, two drivers in turn take the wheel of one car. The maximum continuous time behind the wheel per driver is 1/3 of the race distance.