Citroën’s Team principal Yves Matton declared in mid-summer that their priority was since then to prepare for the 2018 season. The first surprise is that the tests, to date, have been carried out by Andreas Mikkelsen (now engaged with Hyundai for the rest of the season and 2018) and Sebastien Loeb, who seems to be considering a part-time return for the next season with the French team.
The first test was developed in Germany during the first week of August, where Andreas Mikkelsen used the front splitter already used in Monte Carlo Rally this year, as can be seen in the pictures below. This splitter was supposed to be designed for asphalt rallies, but it was not used in Tour de Corse, nor Germany or Catalunya Rallies.
A.Mikkelsen/A.Jaeger, Citroën C3 WRC, test in Germany, August 2017
S.Lefebvre/G.Moreau,. Citroën C3 WRC, Rally Monte Carlo 2017, 9th
Also, Sebastian Loeb tested the same car with this splitter during the test session he carried out later in August in France on asphalt. Pictures taken by Herve Tusoli show the comparison of this front splitter versus (above, Loeb in France) the splitter used after Monte Carlo (Meeke in Finland in the picture below).
Pictures by Herve Tusoli and Citroën Racing
This splitter is thinner and with an elevated central part. Different location of Michelin stickers helps to distinguish between these two configurations.
There is a third configuration of the front splitter, which has been tested by Sebastian Loeb and Stephane Lefebvre in the tests on gravel close to Lloret de Mar (Spain) developed on September 20th. It is a combination of both, as only on both sides the splitter is thinner, while the center part remains unchanged. Picture below, extracted from Jaume Soler excellent video shows this new splitter geometry.
S.Loeb/D.Elena, Citroën C3 WRC, test in Lloret de Mar, September 20th, 2017
The picture also shows the modification tested by Loeb on the dive planes, which have been redesigned and now they start from the upper section of the front wheel arches, leading to dead-end spaces to air. They are very similar to the design used by Hyundai during the present season, shown in picture below, although longer and with no side lips.
D.Sordo/M.Martí, Hyundai i20 WRC, Rally of Sweden 2017, 4th
Also, Ford designed upper dive planes starting from the front wheel arch on their Fiesta WRC 2017.
E.Evans/D.Barritt, Ford Fiesta WRC, Monte Carlo Rally 2017, 6th
It is curious that Hyundai has been testing new dive planes these days also in Catalunya, which are very similar to the original design of the Citroën C3 WRC. Both teams seem to be dealing with similar solutions but in opposite directions.
It is also significant that Loeb complained, at the end of this test, of low grip on the rear of the car in some sections, while all modifications have been introduced in the front part of the car, oriented to improve handling and to reduce understeer.
courtesy of Jaume Soler
S.Loeb/D.Elena, Citroën C3 WRC, test in Lloret de Mar, September 20th 2017
Note that the C3 incorporated a Pitot tube in front of the windscreen, in order to measure the air speed on that specific point, both in Germany and Spain tests. Pitot tubes are widely used to measure the air speed with very little flow disturbance. The principle behind Pitot measurement system is pressure difference, between dynamic measured at the front hole (A) and static pressure, measured in the side holes behind (B).
Pitot tube (picture by Ilde Cuesta)