Grand Touring Under

Grand Touring Under (GTU)’’’ is the name of a former classification designated to grand touring cars competing in sports car racing, originally used by IMSA in the IMSA GT Championship,^[1] and later by Grand-Am in the Rolex Sports Car Series.^[2] IMSA used the class between 1971 and 1994, and Grand-Am used the class for a single season in 2000.^[3] The original class rules specified an engine displacement of under 2.5 L (150 cu in), natural aspiration, and was the secondary class below the top tier class, GTO. The class later became known as GTS-2 in 1995, then GTS-3 between 1996 and 1997, and eventually evolved into the GT3 class for 1998.^[4][5]

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