By the 1970s, Opel had emerged as the stronger of GM's two European brands; Vauxhall was the third-best selling brand in Great Britain after the British Motor Corporation (later British Leyland) but made only a modest impact elsewhere. The two companies were direct competitors outside of each other's respective home markets, but mirroring Ford's decision to merge its British and German subsidiaries in the late 1960s, GM followed the same precedent. Opel and Vauxhall had loosely collaborated before, but serious efforts to merge the two companies' operations and product families into one did not start until the 1970s - which had Vauxhall's complete product line replaced by vehicles built on Opel-based platforms - the only exception to the rule being the Bedford CF panel van, the only solely Vauxhall design which was marketed as an Opel on the Continent. By the turn of the 1980s, the two brands were in effect, one and the same.
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).