colnago
I believe the JGTC cars aren't just "street cars with paint and decals", but more like "silhouettes", where the body panels are made out of lightweight materials and "shaped like" the street car...however they sit on top of racing chassis.
Yep, and more. From the Super GT web site:
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In the world of Hako (Tintop/Sedan-type) racing, the AUTOBACS SUPER GT Series features not only the best racing, but also the greatest variety of participating models of car. In terms of makes involved in the series, there are no fewer than 13 companies present: Toyota, Nissan, Honda, Mazda, Fuji Heavy Industries (Subaru), ASL (Garaiya), Porsche, Ferrari, Lamborghini, McLaren, Vemac, Chevrolet and Mosler are all represented in this most exciting of championships. Regarding manufacturers, no fewer than five countries are represented: Japan, Germany, Italy, Great Britain, and the U.S. all play a big role in the series.
Among these manufacturers, Toyota, Nissan and Honda all support the racing development of their representative models at the manufacturer level. Toyota's Supra, Nissan's Fairlady Z (350Z), and Honda's NSX as entered in the GT500 class all feature works operations specially dedicated to the success of their respective models in SUPER GT. Naturally, this creates a fiercely competitive environment, promoting constant development of the cars. Because of this manufacturer commitment coupled with advanced technology, the SUPER GT Series can boast the highest speeds of any 'Hako' racing series in the world.
The reason for such a high level of performance is the fact that the series' regulations permit a great degree of latitude when it comes to car modification. As long as the cabin area of participating machines is left alone, the area ahead of the bulkhead and behind the cabin can utilize tube frame construction. Suspension modifications are free, and in-board type double wishbone technology, such as used on formula cars, is permitted. Engines can be the standard units as sold in the road-going version of the participating model; or can be another powerplant from the same manufacturer. Adding supercharging components such as turbos is also permitted. Engine orientation (transverse, longitudinal), is also allowed as long as it remains within the original engine bay. Regulations governing transmission position and replacement are also free.
Electronic devices that assist drivers such as ABS and traction control are strictly prohibited, even if these devices are standard on the road-going version of the participating car. Also, carbon brakes are prohibited due to cost escalation. Regarding aerodynamics, there are restrictions in the size and installation location of elements such as spoilers and wings.
Among the wide range of modifications allowed in the series, there are strict regulations governing these modifications. This creates a unique balance, prompting the participation of a wide range of models in SUPER GT.
Minimum weight and rules covering restrictors, engine format and displacement, drive systems and unusual ability in competition create a rivalry that is as finely tuned as the cars themselves. Even curious and uncommon cars can approach this series expecting a closely-fought battle. In qualifying, it's common for the top ten and more cars to line up within a second of pole time. In the races, it's not only the fight for the win that's enthralling; competitors further down the field wage ferocious battles as they hustle for position.
The cars are different, and the possibility for a broad range of machines to win is readily apparent. Because the series provides fascinating and glamorous battles, all kinds of cars participate. In 2005, SUPER GT turned to a international GT racing series, which will encourage non-Japanese works teams to join SUPER GT more.
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They're really, really fast because the rules are wide-open. They're "funny cars", much like NASCAR, not just modified production cars.