TURBO AND EXHAUST
The turbo dominates the YB like a massive anchovy on a baby pizza, and many people think it is the business end of the engine — when in reality it is just another component, and as such needs to be carefully considered to work with everything else in the engine.The standard Garrett T3 found on the Sierra and Sapphire Cosworth is good enough to see you with around 300 bhp, and tricks like cut-back blades, and 360 degree thrust bearings will all help improve performance. The traditional upgrade is the Escort Cosworth’s larger T34 turbo, which can be utilised to give 350-400 bhp. Because they are all based on the same Garrett T3 core, turbo specialists such as Turbo Performance can actually pick-and-mix housings to create a T34 with theT3’s smaller 0.48 exhaust housing, for example, to provide greater peak power than a stock T3 but with less lag than a stock T34.
From there aT38 hybrid will see you well into the 400 bhp power figures, and an even bigger T4-based turbo from the RS500 will take you the rest of the way up to 500 bhp. These upgrades have been proven to work time and time again with great results, but with the development in technology and newer turbos now available the choice has opened up even further. Garrett’s roller-bearing GT range of turbos have been used to great effect on the YB, and the new Borg-Warner EFR series of turbos are showing some very impressive results in terms of both power and, thanks to their twin-scroll design, driveability and quick-spool up too. With so many options available turbo choice is virtually endless and it is best left to the experts to decide what will work best for a given application.
The good news is that the YB’s exhaust manifold is of a twin-scroll design as standard, so is ready to accept a twin-scroll turbo without much fuss. Bigger turbos often require a larger mounting flange, however, so many tuners choose to upgrade to a tubular exhaust manifold — it makes installation of an external wastegate easier too, which many tuners prefer over the OEM internal wastegate as they offer more accurate boost control.