The sight of rival manufacturers reaping the rewards of a successful circuit racing programme prompted Ford to renew its alliance with engine builder, Cosworth, to create the eponymous Sierra, with assembly of the minimum 5,000 units required for 'Group A' homologation commencing in June 1986 at the company's Genk plant in Belgium.

Based on the three-door Sierra bodyshell, the RS Cosworth combined the standard 1,993cc Pinto engine's cylinder block with a forged steel crankshaft and connecting rods, the first time the latter combination had been seen in a production Ford engine.

Topping it off was a Cosworth-developed, twin-camshaft, 16-valve cylinder head fed by a Garrett AiResearch turbocharger, the latter being deemed necessary to achieve a competitive power output for racing, which in time would amount to over 500bhp! Even in standard road trim, the Sierra RS Cosworth produced an impressive 204bhp, its Weber-Marelli engine management system ensuring that performance was delivered ...