Within Opel the Calibra was a car with potential but sadly much of it was unrealised. Valmet Automotive in Finland, who had a manufacturing facility that build Calibras alongside the German plant, produced two handsome convertible prototypes that never saw production. A Saab coupe based on the Calibra was also rumoured but, again, never saw the light of day.
The GSi's engine mapping had been carried out by Opel tuning specialists Irmscher. A model with the 82 PS (60 kW) 1.4 L multi point fuel injected engine, which was otherwise mechanically identical to the GSi, also became available as the Nova SRi in the United Kingdom. In January 1988, a turbocharged version of the Isuzu diesel engine was introduced, with power increased to 67 PS (49 kW).