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;
- Reducing the induction system and exhaust losses.
- Ford Focus RS needed its own, more aggressive performance character so engineers also modified the torque ‘ramp-up’, to enhance performance feel when on boost.
“While we wanted to be equal on low-end responsiveness and minimise the common off-boost inertia of larger turbos, we didn’t want RS to have the same character as ST,” explains Urwin. “We wanted a stronger feel of increasing boost; we wanted you to really feel the surge of the turbo.”
With the turbo spinning, power arrives quickly. The 305PS peak is reached at 6,500 rpm and holds until the 7,050 rpm redline, to allow full use of the top of the power band. After three seconds at this redline, the engine management system recognises no gear shift and then limits revs to the car’s maximum continuous running rpm of 6,500.
“Turbo engines with flat torque curves can often feel like they run out of steam at the top-end, but we wanted to reward drivers who took Ford Focus RS to the red line,” states Urwin. “We’re really proud of the result – strong mid-range transient response and a free revving top-end.”