Grand Touring Over

Grand Touring Over (GTO) is the name of a former classification designated to grand touring cars competing in sports car racing, originally by IMSA in the IMSA GT Championship, and later by Grand-Am in the Rolex Sports Car Series. IMSA used the class between 1971 and 1991, and Grand-Am used the class for a single season in 2000. The class had its origins in the original "TO" class used by the SCCA in the Trans-Am series, and was also similarly modeled to the FIA's Group 4 and Group 5 racing classes, but eventually evolved over time into its own category. The class specified an engine displacement of more than 2.5 L, with engine design and number of cylinders being unrestricted. turbocharging and supercharging was allowed on engines up to a size of 6.0 L. Engines over 6.0 L were required to be naturally aspirated. The original class became known as Grand Touring Supreme (GTS) in 1992.