Citroën C3 WRC 2017 aero (r)evolution

Citroën has been the last manufacturer to officially present his new weapon for 2017, which is the result of an accurate design and a long series of tests. The French team,  retired from 2016 championship to concentrate on the new car and who only took part in selected races, taking advantage of the rule allowing teams not officially competing to carry out up unlimited test days, versus only 30 for the engaged teams, in the 2015-2016 period. The new car incorporates winglets on both sides of car front, side skirts, a complex rear wing and a big rear diffuser. Rear wing supports have a similar shape to those proposed by VW and Hyundai for their 2017 WRC cars, but the wavy shape of the upper plate makes it different from any other car. The waves on the surface could be designed to mix upper and lower flows, in order to reduce flow separation, which would contribute to higher downforce generated by the wing.

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The car’s design started in April 2015, initially by a two people team. One year later, the first tests were developed in Versailles, by Alexandre Bengué, and then at Chateau de Lastours and Fontjoncouse by Kris Meeke and Craig Breen, with the first version of the new car, still using 2016 rear wing. The new car already incorporated a simple rear diffuser, side skirts, wider and planar arches over wheels and a new front splitter.

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Same aero configuration was used in test 2 (May in Algarve, by Kris Meeke and Stephane Lefebvre). Test 3, developed in June by Kris Meeke and Craig Breen in Finland, was mainly devoted to evaluating aerodynamics of the new car. Measures obtained from these tests were used to validate and feedback the numerical modeling work on the new car, made with Computational Fluid Dynamics (CFD) by the Citroën design studio located in Versailles, and then tested with 40% scale models in the wind tunnel of the French manufacturer. Also, the reliability of new aero components was tested.

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Test 4 was developed in Portuguese gravel Algarve roads in July by Kris Meeke, Khalid Al-Qassimi and Craig Breen, with no major changes on the aero package of the car.

First asphalt tests were done on the French roads of Aube (#5) in July, by Kris Meeke and Stephen Lefebvre. A new chassis devoted to asphalt was used, which included a lowered suspension, bigger wheels and bigger brake discs, as well as a specific front bumper for asphalt.

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Test 6 developed by Kris Meeke and Craig Breen near Sanremo (Colle d’Oggia) in August included evaluation of diffuser performance.

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Significant aero modifications were introduced in the second part of test 7 developed in the gravel roads of Algarve by the end of September (after the initial test in Catalan Pyrenees), with Kris Meeke and Stephane Lefebvre. Introduction of dive planes in the front bumper, modification of front wheel arches into a round form, modification of frontal air intakes and, most important, introduction of a new rear wing, with a complex irregular upper plane.

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Picture by ZéGonzo

Rounded rear wheel arches were first introduced in test 8 developed in Huelva (Spain) in October, as well as widened car body behind side doors, and a thinner front splitter.

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Modification in the rear diffuser was introduced in test 9 carried out in Wales in November, by Kris Meeke and Craig Breen, in the form of vertical separators or strakes.

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Picture by JSM Photographic

A new front bumper incorporating the dive planes was evaluated during December tests carried out near Montecarlo rally roads (Hautes Alpes) by Kris Meeke and Stephane Lefebvre. Also, splitter configuration was changed: a thinner splitter with an elevated portion at the center, which will be used in asphalt rallies.

test_c3wrc_montecarlo17_9picture by Etienne Tonelle for Planetemarcus.com

Citroën C3 WRC, test in Southern France, December 2016

Tests were also used to evaluate the reliability of new aerodynamic devices, as shown in the picture below.

test_c3wrc_montecarlo17_lefebvre.jpgAdrien Villemagne

Further information about C3 WRC tests can be found at this link: C3WRC.com.

The official presentation of the new car was done on December 21st, 2016 in Abu Dhabi, confirming that most of the tested modifications were incorporated into the new car.

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Asphalt front splitter was only used in Montecarlo Rally 2017.

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S.Lefebvre/G.Moureau, Citroën C3 WRC 2017, Rally of Montecarlo 2017, 8th

Since Sweden, Citroën has used the thicker front splitter. Location of Michelin stickers shows the different splitter configuration.

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K.Meeke/P.Nagle, Citroën C3 WRC 2017, Rally of Sweden 2017, 12th

Same splitter configuration has been used in the other asphalt rallies in 2017 (Tour de Corse, Germany and Catalunya).

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C.Breen/S.Martin, Citroën C3 WRC, Tour de Corse 2017, 5th

However, asphalt front splitter has been seen in the tests carried out in August by Andreas Mikkelsen (Germany) and Sebastian Loeb (France), car plate EG-485-ZW.

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Seb Loeb test, France, August 2017 – picture by Jeremy Piroton

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Andreas Mikkelsen test, Germany, August 2017 – picture by Hervé Tusoli

Some details of the final configuration are shown below, from pictures taken during Rally Catalunya 2017.

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Detail of rear wing upper plate complex design

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Rear view of the wing and diffuser

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Front bumper and dive planes

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Side view of dive planes

 

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