Cosworth YB series

The Cosworth YB series is a family of 1,993 cc turbocharged four cylinder engines based on the older inline four Ford T88 block, introduced in 1986 in the road going Ford Sierra RS Cosworth with 204 PS. Five thousand cars were built so that the Sierra could be homologated for Group A, for both rallying and touring car racing. Racing versions made around 370 hp, but with the small Garrett T3 turbo reliability was a problem. A limited edition evolution model of mid 1987, the Sierra RS500, of which only 500 were needed for homologation, used a bigger T4 turbo, with power at first around 470 hp and in later years close to 550 hp in full racing trim. The RS500 dominated touring car racing from 1987 to 1992, winning multiple championships and major races. Later evolutions included a reduced emissions road version and the block used in the Escort RS Cosworth, and the engine stopped being used in new cars in 1997.