There are two classes in JGTC...
edit: the JGTC was changed to Super GT for the 2005-2006 season to promote international competition
GT300 - limited from 295hp to 310hp
GT500 - limited from 480hp to 505hp
Competition Rules:
More important than the regulations, the aim of the SUPER GT series is to create competitive and intensely exciting racing. The rules of the series are designed to allow a level of parity seldom seen in modern motorsports. A broader range of teams stand a chance to score well in all events through the use of success ballast (weight handicap), and air restrictor allowances for squads scoring less than favorably in preceding races.
These measures create a platform where intense battles between different rival teams take place event-to-event. Let's take a look at how some of these measures work:
First of all, air restrictors. The amount of air going into any combustion engine at any given time determines the level of power of that machine. In turn, the size of the air restrictor is the determining factor when it comes to the amount of horsepower created by the engine. Cars that are heavier than other competing machinery in either class in the SUPER GT series are given allowances to run larger intake restrictors, thereby creating parity with the lighter, more fleet machines. The system incorporated into SUPER GT rules creates an average within each class of competition, allowing any model within its class a fair chance at top results.
In addition to air restrictors, there is a novel form of weight handicap (success ballast) used for the most successful of competitors. This is also to create parity and greater competition as the season moves on. Competitors who are particularly successful in qualifying and races have to add accumulated kilos based on previous success to their machine's overall weight, allowing the hitherto less successful competitors a fighting chance against their formerly quicker rivals. It also means the most successful teams have to continue fighting just as hard as the lower-ranked outfits all the way through the season for any guarantee of the title.
As a result of the regulations, including the balancing of power-to-weight ratio of competing machines and the weight handicap incurred through previous event success, the 'combat efficiency' of each competing car is maximized. This ensures that each race is as lively and exciting as possible.
Consequently, the top ten and more cars within each class regularly qualify well within a second of pole time; further ensuring closely-fought battles throughout the races. This also sets the scene for something the series has become famous for over the years - a bewildering array of possible champions going into the final event of the season. From the participants' side, it's the most thrilling racing imaginable; while from the spectators viewpoint, there is pure entertainment value right to the flag.