Ford Focus RS (2008)

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;
• 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."

Straight Torque

However, Urwin believes that the power is unlikely to be the first thing drivers will notice, as to get to that redline they will have travelled along Ford Focus RS' 440Nm torque curve.

Offering more torque than any Ford RS production car before it, Focus RS' torque curve has a steady state peak beginning at 2,300 rpm and running to 4,500 rpm, meaning torque can be appreciated in any gear and at most road speeds. The 440Nm peak torque is a 38 per cent increase over Focus ST.

Says Urwin: "Matching low-end responsiveness with a larger turbo and a peak of 440Nm is a real achievement. That's a figure you would only have seen in so-called 'supercars' just a few years ago. It gives Ford Focus RS a gutsy, strong pull at the lower end of the rev range - great for those wanting a powerful performance feel but also great for more relaxed everyday driving."

Bespoke Transmission

That combination of performance ability and cruising capacity is made practical by a specially-developed, six-speed Ford RS transmission. It shares its gear ratios with the Focus ST gearbox on which it is based, with minor modifications to bearings and clutch housing and a revised, stronger differential.

Overall, gearing is one per cent longer than ST due to the larger rolling circumference of Focus RS' specially developed tyres - further evidence of the team's attention to every detail.

This allows gearing long enough for Ford Focus RS to reach the all-important 100 km/h barrier in second gear.

Differential Difference

Putting the torque on the road is aided by a Quaife helical limited slip differential. The Quaife differential was first developed for the original, five-speed Ford Focus RS in 2002, but revised and improved by Ford Team RS for the new, six-speed Focus RS. Today, it features a sixth planet gear and has been revised for increased strength and a more subtle intervention and torque transfer.

Computer-aided engineering drove the design of the differential, identifying the potential areas for increased strength. This was aided by measuring rig work and whole vehicle development, with particular attention to refining performance plots for the differential's torque bias function, to maximise dynamic performance.

Concludes Urwin: "We have tuned the differential for a progressive torque transfer. Our work was focused on creating an optimum drive for both road and track, in the dry and the wet. It was in finding this balance that our tuning efforts were directed."

Performance

Creating the power of a true Ford RS is one thing; managing that power into accessible yet exhilarating performance and assured traction is another. This challenge was met by Ford's renowned vehicle dynamics experts.

Under the guidance of Chief Programme Engineer, John Wheeler, the Dynamics team was led by Chief Engineer, Dirk Densing, whose relaxed demeanour belies his passion and pedigree in performance cars and motorsport.

This team has achieved a car capable of 0-100km/h (0-62 mph) in 5.9 seconds and a top speed of 263 km/h (163 mph).

Wheeler and Densing were determined to create a dynamic mechanical set-up that would provide a pure driving experience, rather than manage power with constant electronic interference or truncation systems.

The most obvious change is the car's wider track, but the team completed their solution with a suspension technology that was under development at Ford's Research & Advanced Engineering centre (R&AE) in Aachen, Germany. Called 'RevoKnuckle', this innovation was identified early on as offering significant benefit to a new front-wheel-drive RS.

The combination of wider track and RevoKnuckle front suspension is the reason Ford has been able to do what was thought impossible previously: develop a 305PS (300 bhp), front-wheel-drive car that is not only driveable every day, but faster in many situations than all-wheel-drive performance cars.

Exhaustive testing and refining in the hands of Team RS' dedicated vehicle dynamics expert, David Put, has also created a set-up for Ford Focus RS that forgives the bumps of every day roads, yet rewards on-track commitment.

"It sounds simple, but is a genuine challenge: make a potent performance machine as accessible and useable as any other Focus; able to transform instantly from everyday transport to track-day 'supercar'," explains Wheeler. "It's a combination of innovative technology and class-leading dynamics, finely honed through David's expertise and commitment that made this possible."

Torque Talk

The greatest engineering challenge was in managing the impact of the car's 440Nm torque. Torque steer - the impact of torque on steering in front-wheel-drive vehicles - is one of the key challenges in suspension development of front-wheel-drive cars.

In the real world, torque steer is most often experienced when hard acceleration, cornering or uneven surfaces are combined and its effects are apparent to the driver as a sudden or momentary disturbance on the steering wheel. This is not 'performance feel', but a transient 'error state' which detracts from steering precision and performance.

Wheeler explains the phenomenon: "Torque steer is experienced when an unequal traction forces exists between the left and right front driven wheels. On a good flat surface, driving straight ahead, the left and right driven wheels have equal driving torque and everything is balanced.

"When left and right torque is unequal then the trouble starts. In the design of front-wheel-drive suspension, two main aspects have to be considered to minimise torque steer: keeping the centre of the outer CV joint on the steering axis line, and minimising the offset from the wheel centre to the steering axis. This is most important in performance cars, where wider wheels create a greater offset to begin with," he continues.

In the physics behind this phenomenon, traction forces at the tyre's contact area with the road are translated in two ways: one force 'couple' transfers harmlessly through the driveshafts, but a second force component acts at the wheel centre. This element creates a turning force about the steering axis. The larger the offset between the wheel centre and the steering axis, the larger the turning torque.

In the design of the suspension geometry, therefore, the first priority is to keep the offset from the wheel centre to steering axis as small as possible.

Even this is not an exact science since, with wide tyres on uneven road, the tyre's contact area with the road can move from the middle to the inside or outside of the tyre.

These unbalanced forces can be exacerbated further by a limited slip differential, as some have a very unforgiving characteristic of locking and applying transfer torque too rapidly.

Considering wide tyres, a wide track and wheel offset and limited slip differential are all present in the front-wheel-drive Ford Focus RS, these areas were the first to be considered by the Dynamics team.

Stopping Power

With such performance capability on tap, it's no surprise to find Focus RS offers a vice-like braking performance. Large 336mm x 30mm, ventilated front discs are gripped by stiffer, single 60mm piston calipers, supported by 302mm x 11mm rear discs. Ford Focus RS also boasts unique high-friction brake material and a tandem brake booster, all combining to generate up to 1.2 g under braking and give Ford Focus RS a stopping distance of just 34.8 metres (114 feet) from 100km/h (62mph).

Anti-lock braking with Electronic Brake Force Distribution (EBD) is standard, as is Ford's Electronic Stability Programme (ESP), here tuned specifically for the car, to allow a high level of sporty driving before intervening.

"In some cars, ESP limits fun for the enthusiast, because it can be used to disguise chassis weaknesses," explains Densing. "In Focus RS, the ESP system is tuned for later and shorter interventions, so you don't feel engine intervention and only occasional brake intervention, even on race circuits, or in rain."

The ESP system can be deactivated for circuit driving. However, this may not always be necessary, as Densing highlights.

"Because it's so precisely tuned, our engineers have lapped the Nuerburgring just as quickly with ESP on, as with it off," he states.

Aerodynamics also played a part in the Dynamics team's work. Says Densing: "Aero is very important to any car, but usually concentrated on not creating lift front to rear. With its sophisticated aero package, Ford Focus RS generates genuine downforce at circuit speeds and we've covered thousands of kilometres refining computer simulations to find the right balance of downforce without too much drag."

The target for high speed stability of a performance car is to position the aerodynamic centre of pressure at a controlled point behind the centre of gravity.

In Ford Focus RS, the starting point was the standard Focus shape, crafted to generate moderate front end and rear end lift at higher speeds. The challenge was to transform this lift into downforce and bring the aerodynamic centre of pressure forward, without undue sacrifice to the drag coefficient and top speed.

Extensive wind-tunnel testing was conducted to refine aerodynamic performance, with a target of delivering about 40 points of downforce at the front and 10 points at the rear.

The resulting aerodynamic elements for Focus RS achieve these targets, creating 26 per cent more downforce than Focus ST, yet with a drag co-efficient (Cd) of 0.38.

The result of all this effort is a car that is not just fast in a straight line. It is the fastest ever car around the infamous handling circuit at Ford of Europe's Lommel Proving Ground in Belgium - known to the team as 'Route 7' - beating even the Ford GT and cementing its dynamic credentials.

In addition, Ford Focus RS has completed over 400 laps (over 8,000km) of Germany's fearsome Nuerburgring Nordschleife during its circuit performance development.

The purpose of all this work was to ensure Ford Focus RS continues and enhances Focus' reputation as a driver's car and stays true to its core philosophy of generating pure driving enjoyment by flattering the novice driver, while rewarding the expert.

Style

Ford Focus RS exudes its intent of being the ultimate Ford performance car of its generation and strikes a lasting impression with performance car enthusiasts.

"Kinetic design visualizes the dynamic qualities of a vehicle, transmitting a feeling of driving excitement, but true to the character of each vehicle," explains Ford of Europe's Executive Director of Design, Martin Smith. "In design terms, every member of the Ford of Europe family has its own personality. Mondeo is the most premium; Fiesta the most stylish; Ka the friendliest - RS is quite simply the meanest!"

In design as in concept, Ford Focus RS is inspired by Ford's World Rally Championship success and this is most obvious in its large, gloss-black front trapezoidal air intake, creating an immediate visual link to the Focus World Rally Car - design for the road, true to motor sport principles.

Heightened aerodynamic and cooling needs meant Focus RS required a specific design approach that integrated these requirements and differentiated it from mainstream Focus aerodynamic elements.

Rather than settle for grafting performance detailing onto a standard body shape, designers have revised almost every body panel on Ford Focus RS to create its bespoke shape.

The result is cohesive and dramatic; new front and rear bumpers and integrated side rocker mouldings give Ford Focus RS a lowered, meaner appearance, while a revised bodyside with wider wheel arches, rocker mouldings and vents give the vehicle a more purposeful stance. These are topped by possibly the most dramatic of Ford Focus RS exterior features, the imposing rear spoiler, inspired directly by the Focus World Rally Car.

Necessary aerodynamic elements are contrasted with the body colour of the car by a gloss-black finish and together they provide some of the vehicle's more distinctive styling cues.

• Smaller, secondary cues provide visual differentiation to mainstream Focus models:
• Twin panels of louvres on the bonnet and small vents underneath the headlamps reinforce the car's performance intent and augment the recognised Ford Focus shape;
• RS badges throughout the car reinforce the car's RS pedigree: three dimensional RS badges are present on each front wing vent, the upper radiator aperture, tailgate and embossed on each wheel;
• 19-inch, 15-spoke polished alloy wheels echo the look of their World Rally equivalents.

"Imagine a Focus WRC roaring through a stage in Monte Carlo - you know immediately what it is from front graphics, flared arches, and distinctive livery. Our intention is to make Focus RS equally and immediately recognisable." states Smith.

Performance Design, Aerodynamic Purpose

Ford Focus RS' major design features are all functional, as well as styled to create a lasting impression, with each doing an important job in managing the airflow over and into the car.

"A high performance car like Focus RS has very different and much more sophisticated cooling requirements than a standard car, so design works hand-in-hand with aerodynamics," explains Chief Exterior Designer, Stefan Lamm. "RS is also lower and wider, not only to give the right impression, but also to ensure more downforce and less uplift than Focus ST. This is fundamental for responsive high-speed handling on circuits."

From the outset, Team RS worked with Ford's design and aerodynamics specialists to ensure performance style met performance requirements. The prominent front air splitter, twin-blade rear spoiler and rear venturi all underwent significant aerodynamic testing to achieve the right cooling and aerodynamic targets.

For example, while echoing the standard Ford trapezoidal silhouette, the front splitter's intake area and structural cross bars have been precision honed to allow the required volume of air into the car's cooling system.

The gloss-black front splitter also has a role in controlling exterior airflow, working with the rear venturi in managing air movement under the car, to help develop the required downforce for circuit use. The venturi then channels the air bisected by the front splitter, directing it out from underneath the car and past the rear bumper.

Significant aerodynamic analysis went into the design and construction of the rear venturi tunnel and rear spoiler. Here, Ford's World Rally expertise came into its own to determine the precise height, ramp angle and position of the car's twin-blade spoiler, for maximum aerodynamic efficiency.

Explains Lamm: "Customers would expect an RS to have a rear spoiler, but on Ford Focus RS this has been designed very precisely. A large front splitter creates a large aerodynamic force at the front and could make the rear light and nervous in high speed handling. So, the rear spoiler and venturi have been developed painstakingly to balance the downforce between front and rear. In a true high-performance car like Ford Focus RS, this ability to collect, extract and manage airflow efficiently is critical to its design."

Distinctive Colour Options

To reinforce the bold, new, motorsport-inspired design, designers knew colour was as vital ingredient of the overall Ford Focus RS package.

The positive reception given to the signature 'Electric Orange' colour that became a highlight of the Focus ST launch encouraged the Design team to develop an equally exciting and unique 'hero' colour for the sportier Focus RS.

Their inspiration for the vibrant, new 'Ultimate Green' came from the livery of Focus World Rally Cars. The colour reflects the green signature colour of Ford's global partner and World Rally Championship sponsor, BP, and also stands as a modern interpretation of the 1970s Ford Escort RS Le Mans Green colour.

"Ford Focus RS is a car designed to grab your attention and the choice and use of colour is vital," says Stefan Lamm. "Colour can define a brand, as we saw with Focus ST and in this case we wanted something even more energetic and dazzling. Green is a critical colour that has to have the shade tuned perfectly and 'Ultimate Green' captures and communicates the spirit and energy of Focus RS."

Ford Focus RS will also be available in the classic RS choice of Frozen White or Ford Performance Blue, the colour of the original Focus RS.

In each case, body colour is used not just in contrast to the gloss-black exterior elements, but also extends to the car's interior.

High-Performance Interior

On the inside, Ford Focus RS boasts a unique and appropriately performance-oriented interior, designed to appeal to customer tastes and balance genuine sports performance with a strong sense of style and quality.

The cabin is dominated by bespoke Recaro high-performance sports seats, specially designed and trimmed in an authentic motorsport microfibre, a tactile material that also provides the grip and support necessary when driving enthusiastically. Each is colour-matched to the exterior, with ebony leather accents and 'RS' and 'Recaro' logos stitched into each backrest. Alternatively, optional Ebony black, partial-leather seats will be available with all exterior colours.

Elsewhere, colour builds on the sporty interior theme introduced in Focus ST, with even bolder performance styling, more use of colour matching to the exterior and wide use of metallised and carbon accents.

Rear seats are sculpted, featuring the same detailing and high side bolsters as the front sports seats, making Focus RS a genuine four-seat vehicle.

The centre console is finished in a stylish, carbon-look trim and metallised highlights include air vents, door grab handles, switchgear and gearshift surround and unique RS-branded scuff plates on the door sills. These highlights contrast with a black-trimmed roof lining, emphasising the sporty, cockpit feel.

The driver is also reminded this is no ordinary Focus at every touch, with each interaction refined to match Ford Focus RS' sporty character.

At the centre of this experience is a chunky, three-spoke steering wheel with RS signature and shorter-throw gear lever, with a slick, precise action and a six-speed gear shift graphic in RS blue. The performance driving environment is completed by aluminium foot pedals and three additional gauges, including turbo pressure, sitting atop the centre console and angled toward the driver.

Green or blue interior options are available, matched to the Ultimate Green or Performance Blue exterior options. Frozen White interior colour is blue.

Explains Martin Smith: "Just as the exterior must describe performance potential, so the interior must create a genuine sporting environment, in looks and performance. For example, the use of microfibre is tactile and grips occupants, while a branded Recaro seat communicates immediately an authentic motorsport capability."