aluminium honeycomb floorpan, to which was secured a chrome-moly steel spaceframe. DMC's brief to Owen Ashley stated that as much of the standard Calibra silhouette as possible had to be retained. To that end, a standard Calibra roof, side body monocoque pressings, doors and rear window were used. All remaining bodywork was moulded in fibreglass. The car was powered by a Buick 3800-derived, 3.5-litre all-aluminium odd-fire V6, similar in specification to that used on the IMSA Corvette GTP. Built in the United States by Ryan Falconer, the engine retained its original single-cam, pushrod-and-rocker, two-valves-per-cylinder layout, but employed a Racetronics engine management system and Garrett turbocharger aspirating through a 52mm restrictor plate. The engine produced approximately 600 BHP (447 kW) in race trim. Power was delivered to a rear-mounted five-speed manual Hewland transaxle through a carbon-fibre propeller shaft. Fuel capacity was 40 litres, and double-wishbone suspension was used at both the front and rear ends of the car. Driven by Michael Briggs, the car was campaigned from 1991 to 1993. A rule change for 1994 that banned turbocharged engines from the series, as well as the rapidly increasing popularity of Group A super touring cars, compelled DMC to retire the Calibra in favour of devoting its motorsport budget and resources to its two-car Astra super touring effort. Rallying The Calibra Turbo was also rallied, albeit without notable success. A Calibra finished ninth in the 1992 Sanremo Rallye, with Bruno Thiry at the wheel. This did make it the fastest car in the 1600 to 2000 cc class. 1992 Calibra Cabrio Prototypes Although the Coupé shape was so successful, that it was no real demand for a Calibra Cabrio, Valmet Automotive was entrusted by Opel to build fully functioning convertible Calibra prototypes, as competitors also started mid-size convertible development. Valmet Automotive built two red coloured prototypes in 1992, with the 2.0 litre, 8 valve engine. A third body was also produced for use in flexibility tests. With the convertible body, the Calibra lost the practicality of the rear seats and the boot, thus the design was not further developed. Now a red painted prototype is exhibited in the underground garage of Opel Classic at the concept car section. 1997 Calibra B Design Study In 1996 Opel began the development of the successor of the Calibra on the basis of the Vectra B, but it didn't fit the international model strategy of General