Aerodynamics of WRC2 cars: Citroën C3 R5

One year after the debut of the car in the Tour de Corse 2018, it’s time to review the aerodynamics and WRC2 performance of the Citroën C3 R5. The C3 R5 is the second attempt of the French manufacturer into the category, after the unsuccessful Citroën DS3 R5, which never showed enough performance to fight against the category leaders Fiesta R5 and Fabia R5.

Y.Bonato/B.Boulloud, Citroën C3 R5, Rallye Monte Carlo 2019, 1st WRC2

For this reason, the new C3 R5 design process, initiated in June 2016, started from a blank page, rejecting to use any of the DS3 R5 parts. The design team included Jean François Grangclandon (car designer), Olivier Maroselli (project manager) and Pierre Budar (by then Customer competition car development manager), who was later replaced by François Wales when he was promoted to Team Manager. The goal was to create the car that would become the reference in the category, in terms of performance, reliability and exploitation costs.

The C3 R5 includes some parts from selected Citroën suppliers, such as Sadev (transmission) and Reiger (suspension). In opposition with all the other R5 cars, the suspension design has two versions, one for gravel and one for asphalt, similar to the WRC cars. The front struts are angled towards the rear for asphalt, and to the front for gravel.

The C3 R5 front bumper includes a big air intake, smaller than that of the C3 WRC, and with no additional intakes for brake cooling, while the air vents on the bonnet are the same as in the case of the C3 WRC.

Y.Bonato/B.Boulloud, Citroën C3 R5, Rallye Monte Carlo 2019, 1st WRC2

The front bumper includes a modest splitter, which is only prominent in the central part of the bumper, but not on both side extremes.

picture by Patrik Pangerl – eWRC.cz
S.Lefebvre/G.Moreau, Citroën C3 R5, Wales Rally GB 2018, 5th WRC2

Prominent wheel arches are included in front and rear axes, with a design very similar to those of the Fabia R5 or the Polo GTI R5. Also, small side skirts are present.

G.De Mevius/M. Wydaeghe, Citroën C3 R5, Rallye Monte Carlo 2019, ret.

In the rear of the car, the main feature is the absence of a rear diffuser in the rear bumper.

S.Lefebvre/G.Moreau, Citroën C3 R5, Rally Catalunya 2018, 15th WRC2

The rear wing is supported by two swan-neck supports, located at one and two thirds of the wing length. The supports are attached to small vertical fins located on the upper side of the wing, allowing to get used of additional side force when cornering, as we saw in our post about rally cars sideways. The wing also includes endplates and Gurney flaps.

picture by rallysprott
S.Tempestini/S.Itu, Citroën C3 R5, Wales Rally GB 2018, 7th WRC2

Note that these flaps, located at the rear of the wing, are bigger on the external sides of the swan-neck supports than in the central part (between supports). This is probably due to the presence of the roof scoop aligned with the center of the wing, which perturbates the air flow in the car center, reducing the efficiency of the flap in this area.

Like in the Fabia R5, the rear wing is not completely flat, but bends at the ends, following the shape of the car roof.

picture by Citroën Racing
S.Lefebvre/G.Moreau, Citroën C3 R5, Gravel test, Mazamet, September 2017

Although some parts had already been separatedly tested before, the first full car test took place on the gravel routes of Mazamet (South of France) in September 2017, with Stéphane Lefebvre, Craig Breen and Yoann Bonato sharing the wheel.

picture by RV Motorsport – Planetemarcus
Citroën C3 R5, asphalt test, France, September 2017

Later that month, the car was tested on French asphalt routes, also by Lefebvre and Bonato.

picture by Anna Solé Genescà
C.Breen/S.Martin, Citroën C3 R5, Gravel test, November 2017, Cardona

The decision taken by the FIA in the August 2017 meeting, by which paddle gear shift systems were banned in R5 cars (even though they were initially allowed), in order to keep costs down, represented a significant delay in the preparation of the car, as the team had devoted significant efforts to the development and testing of this system.

As Budar declared to Motorsport News then: Now we have to rework the hydraulic pump, redesign all of the electrics on the center [transmission] tunnel. Because we have the paddle, we have the handbrake much closer to the steering wheel – now we have to move this to make space for the shift and the cost is big for us.

The team estimated the impact of this change in an additional two months of development, for what the initial plan of homologating of the car before Rallye Monte Carlo 2018 had to be postponed.

picture by @World
Y.Bonato/B.Boulloud, Citroën C3 R5, Rallye de Var, course car

In the next months, other tests were developed in Fontjoncouse and Cardona, with other drivers such as Kris Meeke, Yohan Rossel, Paolo Andreucci or Simone Tempestini testing the car. But the first real test came in November 2017, when the car was invited to take part as course (zero) car in the Rallye de Var, with Bonato at the wheel.

The car finally received the homologation in March 2018, so the car debut took place in the Tour de Corse 2018, with Lefebvre/Moreau as official drivers and Bonato/Boulloud in a customer version, incorporated
into the works team for this round. A third car was driven by Alexandre Bengué and Thomas Chauffray as course (zero) car.

picture bu Honza Fronek – eWRC.cz
S.Lefebvre/G.Moreau, Citroën C3 R5, Tour de Corse 2018, ret.

The car confirmed its potential from the very first stage, when Bonato was second behind the Škoda Fabia R5 of Kopecký, while Lefebvre won the second and fourth stage, completing a very promising first leg. Unfortunately, he had to retire on the second day after having an accident, but Bonato constantly placed the car on top positions, to end in the second position of the podium.

picture by Rally Cow – eWRC.cz
Y.Bonato/B.Boulloud, Citroën C3 R5, Tour de Corse 2018, 2nd WRC2

The plan for the season was to attempt to win the WRC2 championship with Lefebvre as the regular official driver, in order to show the potential of the car and convince customers to buy the C3 R5. To achieve this goal, the plan was to compete in six other events.

picture by Johann Dubee – eWRC.cz
Y.Bonato/B.Boulloud, Citroën C3 R5, Rallye Lyon-Charbonnières Rhône 2018, 1st

Only 3 weeks after Corsica, Bonato gave the C3 R5 his firts absolute win ever, by finishing first in the Rallye Lyon-Charbonnières Rhône 2018, a tarmac event of the French National Championship.

picture bu Honza Fronek – eWRC.cz
S.Lefebvre/G.Moreau, Citroën C3 R5, Rally Portugal 2018, 3rd

Second participation of the C3 R5 in the WRC2 Championship took place in Portugal. And the rally started really well for the French team, as Lefebvre won the first long gravel stage (Viana do Castelo), reaching the leaderboard. Two punctures prevented him from winning the event, but not to finish in a rewarding third position, to get the second podium of the year.

picture by Citroën Racing
S.Lefebvre/G.Moreau, Citroën C3 R5, Rally Sardegna 2018, 8th WRC2

Sardegna saw another strong charge from Lefebvre’s C3 R5, who won four stages before retiring with a broken suspension arm, while in Finland he had a soon retirement as he lost part of the rear axle on SS2. Germany also brought early punctures for Lefebvre and Bonato, but still there was time for Lefebvre to setting the fastest time on the selective Panzerplatte stage. Simone Tempestini on a customer car was second in Turkey, while Lefebvre finished in a promising fifth position in Wales.

O.C.Veiby/S.R.Skjaermoen, Citroën C3 R5, Rally Catalunya 2018, 9th WRC2

In the last event of the season, in Catalunya, all three cars suffered from different problems and had to restart in super rally, with the eight position of Veiby/Skjaermoen as the best result of the team.

The final goal (the title) was not reached, but the car showed good performance and reliability. And, most important, by the end of the year the team had received up to 44 orders for a customer car.

Season 2019 saw the birth of the new WRC2 Pro (Teams) Championship, in parallel to the existing WRC2 (drivers) trophy. Citroën decided to officially start fighting for the WRC2 Pro title in Sweden, while in Monte Carlo Bonato was inscribed with a PH Sport (customer) car, only for the driver’s classification.

Y.Bonato/B.Boulloud, Citroën C3 R5, Rallye Monte Carlo 2019, 1st WRC2

Bonato complete a superb rallye in the French Alps and drove the car to the top of the podium, giving it its first win in the WRC2 series.

M.Ostberg/T.Eriksen, Citroën C3 R5, Rally Sweden 2019, 1st WRC2 Pro

The pair Mads Østberg/Torstein Eriksen were designed by Citroën to defend the French manufacturer in the WRC2 Pro Championship during the whole season, driving a car run by the Belgian Team DG Sport. And they couldn’t have started better, as they won the Rally Sweden in their category, in spite of dealing with a car not really suited for snow conditions. But the Norwegian completed a faultless event and ensured the first top-scoring position in their return to the category.

The next appearance of the Citroën C3 R5 will take place this week in Corsica, again with Bonato/Boulloud and De Mevious/Wydaeghe in the WRC2, while the next appearance of Østberg/Eriksen in the WRC2 Pro has been programmed for Argentina.

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