Saturday, 25 June 2011
Ford Focus RS
The Ford Focus RS engine shares its fundamental structure with that of Focus ST, but there the similarities end. Powertrain manager Len Urwin knew from the beginning that simply adjusting the engine management system for more power would be insufficient for a true RS.
He explains: "There was never an intention to try to 'chip' the ST engine. We evaluated several approaches using the ST engine and none gave us the combination of power delivery, character and durability that we wanted, so we opted to create an RS Duratec, using the ST unit as our base."
The objective was increasing power and torque without affecting durability. To meet that, multiple detail changes were made to the powertrain including a revised cylinder head gasket, ultra-durable metal sprayed cylinder bores, revised pistons and a bespoke camshaft profile and connecting rods, allowing bigger small end bearings.
However, the most obvious changes are the new intake system, exhaust manifold and turbocharger. The larger Borg Warner K16 turbo fitted to Ford Focus RS offers a maximum steady state boost pressure of 1.4 bar - double that of Focus ST's 0.7 bar - to generate the car's 35 per cent power increase.
Committed to maintaining responsiveness of the engine, Urwin's team focused on three areas:
- Integrating the turbo with the exhaust manifold, to allow subtle manifold tuning and strategically locating the turbo in the engine bay, to optimise crash performance and minimise revision to the exhaust system and associated oil and water pipes;
- Carefully sizing the required larger turbo, to closely match the 'bottom end' engine responsiveness of Focus ST;
