document : Citroën Racing's new asset in World Rally Championship


Citroën Racing's new asset in World Rally Championship
information supplied by: Citroen 30 September 2010

CITROËN DS3 WRC
 
CITROËN RACING’S  NEW ASSET IN WORLD RALLY CHAMPIONSHIP
 
Pursuing its involvement in top-class road racing, Citroën Racing has unveiled its new DS3 WRC, due to take part in the 2011 season of the World Rally Championship. Citroën DS3 WRC complies with the brand new regulations drawn up the FIA and is packed full of Créative Technologie.
 
The compact, dynamic and aggressive design of this ‘little racer’ immediately catches the eye – it has clearly been designed with winning in mind with its widened wings, redesigned bumpers and aerodynamic features. Built using the production body shell, the chassis has undergone many modifications to adapt the four-wheel drive transmission and the McPherson-strut suspension system. The safety of the driver pair is guaranteed by a roll cage, which enhances the sturdiness of the car.
 
Compared with the previous generation of World Rally Cars, the 2011 regulations have led to a genuine revolution under the bonnet. Citroën DS3 WRC is powered by a four-cylinder, 1600cc turbocharged direct injection engine. A first at this level of motorsport, the use of a direct injection engine opens up new possibilities for the development of racing engines, especially in terms of fuel consumption. Designed and built from start to finish by Citroën Racing, this engine develops a healthy 300bhp.
 
Certified and supplied by Sadev, the six-speed sequential gearbox is coupled with front and rear differentials. Semi-automatic controls and the central differential are now prohibited. In order to keep costs under control, the FIA has also defined the characteristics (dimensions, weight, price, etc.) of the car’s main components. Taking these constraints into account, Citroën Racing and Sadev’s engineers looked to maximise performance and reliability by focussing on every last detail.
 
Deemed to be efficient, balanced and easy to handle by drivers during initial testing, Citroën DS3 WRC will have the job of adding to the large collection of titles and race wins racked up by Xsara and C4 WRC.
 
BODYWORK AND CHASSIS: COMPACT AND AGGRESSIVE DESIGN
 
Fine-tuned during extensive wind tunnel testing, Citroën DS3 WRC’s bodywork accentuates the curves of the original model. The wings and the bumpers have been redesigned in order to attain the maximum authorised width of 1,820mm and to accommodate the 18-inch wheels (tarmac version). The front bumper now includes an aerodynamic splitter, whilst a stylish rear spoiler has been attached to the tailgate. The doors have also been altered, with the installation of polycarbonate fixed frame windows and the injection of foam designed to absorb energy in the event of a side impact.
 
Built using the production body shell, the DS3 WRC chassis includes a roll cage made of over 40 metres of steel tubing. The lower part has undergone several significant structural modifications:
  • Upper attachment points added for the rear McPherson-strut suspension
  • Optimisation of the lower suspension attachment points
  • Integration of the transmission tunnel and the rear differential
  • Lateral reinforcements added level with the body sills
 
Since DS3 is more compact than C4 WRC, Citroën Racing’s engineers worked on improving the position of each component so as to achieve the best possible balance between the car’s centres of inertia and centres of gravity.
 
ENGINE: THE DIRECT INJECTION REVOLUTION
 
Since ground link system regulations have only undergone minor modifications compared to the previous generation of World Rally Cars, design office engineers were able to make the most of their experience, deploying solutions that have proven successful on C4 WRC.
 
The McPherson-strut front and rear suspension systems have latitude that enables the position of the attachment points to be optimised. In order to keep development and running costs down, it is now only possible to certify one type of pivot. DS3 WRC uses the same part at the front and the rear, on both the gravel and tarmac versions. The struts are connected using an interface part that varies according to the version. Just like its big sister, the C4 WRC, the four-way adjustable shock absorbers (low- and high-speed compression and rebound) have been designed and built by Citroën Racing.
 
Slightly smaller than  on C4 WRC in order to comply with the 2011 regulations, the 355mm (tarmac) and 300mm (gravel) brake disks at the front, and the 300mm brake disks at the rear, come with  four-piston callipers. A water-cooling system improves the efficiency of the brakes on tarmac.
 
TRANSMISSION: FOUR-WHEEL DRIVE FOR ALL SURFACES
 
With special stages on icy Swedish roads, rough gravel tracks in Greece and smooth Catalan tarmac, DS3 WRC will need to cope with both varied and demanding road surfaces. Although it is without any electronic assistance, the four-wheel drive transmission has been designed to maximise performance in all conditions.
 
The 2011 regulations require constructors to select a supplier that has met the specifications drawn up by the FIA. They set the weight and price of each element. Citroën Racing has signed a technical partnership agreement with the French company, Sadev.
 
The six-speed sequential gearbox and the front differential are integrated in an aluminium housing. These are connected to the rear differential via a longitudinal drive shaft. The central differential is now prohibited, but a system may be used to disconnect the rear wheels when using the hydraulic hand brake. Semi-automatic, steering wheel-mounted controls are also outlawed, and have been replaced with a totally manual gearshift lever.
 
As with the engine, the lifespan of the gearbox increases with the 2011 sporting regulations. At one point in the season, teams must use two gearbox/rear axle assemblies for three rallies. 
 
IN DETAIL
 
ONBOARD ELECTRONICS
Drawing on a wealth of experience, DS3 WRC’s onboard electronics are  directly derived from the C4 WRC. The multiplexed electrical wiring harness, the powerbox and all electrical controls are designed by  Citroën Racing. The source code of the internal software is submitted to the FIA, which also has access to the engine and chassis data acquisition system.
 
SAFETY
Aware that safety can always be improved, engineers looked to boost the protection and comfort of driver pairing beyond the levels required by the regulations. Citroën Racing has, for example, developed its own bucket seat.
 
ERGONOMICS
The compact design of DS3 WRC offers drivers an excellent view of the road. A colour LCD screen located behind the steering wheel shows the key information (engine speed, gear selected). The position of the gearshift and handbrake levers has been carefully designed so that they are placed as near as possible to the steering wheel. With a lower seat position to improve his centre of gravity, the co-pilot has his own screen, fixed to the transmission tunnel.
 
DEVELOPMENT: THE ‘LITTLE RACER’ IN ACTION
 
A s the main features of the 2011 regulations were not defined until autumn of 2009, the design of DS3 WRC only really began at that point. In order to begin development work as early as possible, a development mule was built at the end of 2009. Featuring the C4 WRC’s engine with reduced turbo boost, engineers were able to work on the transmission, now stripped of its central differential. Testing continued in the first half of 2010, on both gravel and tarmac roads.
 
After running it on the test bench in April 2010, the 1600cc turbocharged direct injection engine was fitted to the first DS3 WRC. The first track outing of a full DS3 WRC took place on July 23 on the Satory racetrack, a stone’s throw from Citroën Racing’s plant in Versailles.
Philippe Bugalski, Sébastien Loeb, Dani Sordo and Sébastien Ogier took it in turns to contribute to the development of DS3 WRC. The increased lifespan of components – up to six rallies for one engine – meant that long endurance sessions in the most testing of conditions were necessary.
 
DS3 WRC is set to make its official competitive debut at Rally Sweden (10-13 February), the first round of the 2011 FIA World Rally Championship.
 


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Tags | 2011 Citroen DS3 WRC | Motorsport | Citroen |