IMSA GT classes

[4] Grand Touring Under (GTU) was a classification originally used in the IMSA GT Championship,[5] and later by Grand-Am in the Rolex Sports Car Series.

[11] These cars were All-American, V8-powered, used a maximum of 5 forward gears, and used a steel tube frame (similar to the type used in the SCCA Trans-Am Series), and were designed to compete against heavyweight European manufacturers and machinery of the time, such as Porsche and BMW, who were dominating the series at the time.

Nissan then took control of the series in 1988, but faced challenges from Jaguar, Porsche, and Toyota throughout the next three years.

Toyota was quickest in 1992 and 1993, at the end of the GTP era, as Dan Gurney's All American Racers team campaigned the Eagle Mk III, a car so dominant that it has been blamed for the demise of the class.

[21] Camel Lights cars also used the same decal[22] There were many other manufacturers in the GTP class, such as URD Rennsport, Spice, Intrepid or Gebhardt, and in the early 1990s, Mazda.

[20] Bishop would stand down as president in favor of Mark Raffauf, who was his deputy, and its representative on the ACCUS board.

He proposed a follow-up open-top Porsche powered racer which would also be sold to customer teams.

Critics predicted that the decreased variety of cars would disappoint race fans, and in fact, it did finally kill the series in 1993.

[20] GTP cars ran their last race on October 2, 1993, at Phoenix International Raceway.

[24] The GTP category was credited for many innovations in the U.S., including antilock brakes, traction control, and active suspension.

[20] Grand Touring Supreme (GTS) is a former classification originally by IMSA and later by Grand-Am in the Rolex Sports Car Series.

This changed again in 1997, when the GTS-2 (former GTU) class became known as GT3, due to the addition of a new GTS-2 category, which allowed for existing international GT2 cars, like those used in the FIA GT Championship.