theres differant yb's. theres yb........... ahh fuck it.

YB Series Ford Sierra EngineType Year Size Output Description
YAA 1984 1993cc
In-house project, 16 valve, twin cam belt drive on Pinto block for small manufacturers, 3 built
YBA 1984 1993cc 200 Bhp.Prototype YBB, 10 built
YBB 1985 1993cc 204 Bhp.
Turbo YAA commissioned by Ford for Sierra RS Cosworth, 5000 built for homologation
YBC 1986 1993cc 280-300Bhp.Group A rally engine
YBD 1987 1993cc 225 Bhp.Evolution YBB used in Sierra RS500, more turbo, 8 injectors, 500 Bhp in race tune
YBE 1987 1993cc--Ford Undustrial Customer Engine, non-Cosworth covers, used in Panther Solo
YBF 1987 1993cc 400+ Bhp.Race version of YBD
YBG 1989 1993cc 207 Bhp.U.S. emmissions capable model
YBH1989----not yet disclosed YBJ19891993cc207 Bhp.Similar to YBG, emmissions engine

yaa follows on from other cosworth engines like for example tge gaa,oaa,waa, so a yaa was on the cards and the yb was a development.