Thank you, readers for engaging with the puzzle I set during the summer and which I have so far neglected to return to. Relief is at hand!
The question was “What is the connection between the Opel Vectra “A” and the Rolls Royce Silver Seraph?” If you wish to find out the answer you must simply carry on reading.
The Opel Calibra was based on the Opel Vectra “A” which appeared in the market in 1988, as a saloon and hatchback (but not an estate). The Astra estate covered that market more than adequately plus the Opel Frontera was due in 1991 in both 3 and 5 door styles.
So, sans estate, the Vectra replaced the Ascona “C”. A year later the Calibra appeared in the European market, made first in Ruesselsheim, Germany, and later on at the Valmet factory in Finland. The Vectra had a 4-wheel drive option plus available V6 engines which meant the Calibra was able to make use of those features. (Ford, as usual, didn’t really bother to put up much against the Calibra until the Mk 2 Probe of 1993, a good 4 years later).
Turning to the other side of the pair: the Rolls Royce Silver Seraph. It had the naturally-aspirated BMW V12 fitted, which Car considered too noisy and high pitched. Bentley’s Arnage twinned the Rolls and received BMW’s 4.3 litre V8 as a means to distinguish it.
So, now the link between the Bentley and Calibra. The Arnage’s V8 engine bottom end was standard BMW stuff as were the four-valve twin-cam heads. The Arnage version of the V8 had a twin-turbo and the design for this was by Cosworth. Why Cosworth? Vickers, the owners of Rolls Royce and Bentley, owned that too.
Cosworth’s boffins used the same twin-turbo concept on the GM C20LET engine in the Calibra 4×4: “on each cylinder bank a water-cooled turbo housing is cast into the manifold itself” (Car, June 1998). With the turbo so close to the exhaust valves the throttle response could be faster as in the turbo would react more quickly to the exhaust gas flow than if it was situated further away. And presumably the exhaust gasses were hotter, reducing the tendency for the turbo to get caked with condensates and carbon.
So, that’s the link: Cosworth used the same concept for their work on the GM engine used in the Calibra as in the Arnage’s V8; the Vectra is related to the Calibra and the Arnage related to the Rolls.