Grand Touring Over

Grand Touring Over (GTO)^[1] 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,^[2] 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.^[3] The class specified an engine displacement of more than 2.5 L (150 cu in), with engine design and number of cylinders being unrestricted. turbocharging and supercharging was allowed on engines up to a size of 6.0 L (370 cu in). Engines over 6.0 L (370 cu in) were required to be naturally aspirated. The original class became known as Grand Touring Supreme (GTS) in 1992.^[4]

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