Used since the current FIA regulations came into effect in 2011, the DS3 WRC is packed full of Créative Technologie. It was the World Champion car in 2011 and 2012, and has proved a wor- thy successor to the Xsara and C4 WRC.
COMPACT AND AGGRESSIVE DESIGN
Fine-tuned during extensive wind tunnel testing, 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 autho- rised 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 attach- ment points added for the rear McPherson-strut suspension, optimisation of the lower suspension at- tachment points, integration of the transmission tunnel and the rear differential, lateral reinforcements added level with the body sills.
GROUND LINK SYSTEMS: THE HUNT FOR EFFICIENCY
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 already proven their worth. The three-way adjustable shock absorbers (low- and high-speed compression and rebound) have been designed and built by Citroën Racing.
Slightly smaller than before in order to comply with the 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.
THE DIRECT INJECTION REVOLUTION
Housed in a machined aluminium block, the exquisitely crafted four-cylinder 1600cc engine complies with the requirements of the regulations, which stipulate in particular a minimum weight and a position for the centre of gravity. It is on the car’s 16-valve cylinder head that the main change has taken place. Mandatory in WRC, direct injection posed a real challenge for the engine specialists at Citroën Racing. Fuel is only mixed with air once it has been injected into the combustion chamber.
Compared with older two-litre turbocharged engines, the reduction in capacity combined with the limited booster pressure results in a slight drop in power output, which is compensated by direct injection, whilst torque is pretty much halved. Each car cannot use more than three engines during the season.
FOUR-WHEEL DRIVE FOR ALL SURFACES
With special stages on icy Swedish roads, rough gravel tracks in Sardinia and smooth Catalan tarmac, DS3 WRC has to cope with both varied and demanding road surfaces. Although it is without any elec- tronic assistance, the four-wheel drive transmission has been designed to maximise performance in all conditions.
The ‘World Rally Car’ regulations require manufacturers to select a supplier that has met the specifica- tions drawn up by the FIA. The weight and price of each element are set by the regulations. 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 pro- hibited, but a system may be used to disconnect the rear wheels when using the hydraulic hand brake.
Like the engine, the lifespan of the gearbox is restricted by the regulations. The manufacturers must choose one link of four rallies, one link of three rallies and two links of two rallies in which they must use the same transmission.
EVOLUTIONS FOR THE 2015 SEASON
To start this season, the DS 3 WRC receives numerous evolutions such as: engine, suspension, aerodynamics, gearbox… The efforts were focussed on the engine in order to get more power and torque, whilst also improving reliability. The steering wheel-mounted paddles for the gear changes are reintroduced after being banned since 2011. Other significant improvements have been made to the aerodynamics, with a new spoiler, as well as to the weight distribution with the use of lighter parts. The kinematics of the rear suspension have also been modified.