Work on the Group B programme began in 1983, with the BX selected as the base platform. Development was overseen by Citroën's commercial services department rather than a dedicated competition division, a decision that shaped the car's compromised architecture. Homologation rules required that the BX's fundamental structure and as many production-series components as possible be retained, constraining the engineers' options. The 20 competition hulls were built by Citroën's competition department based in Trappes, with bodywork produced by Heuliez. Initial testing in December 1985 immediately exposed three fundamental problems: the car was too heavy, lacked sufficient power, and its hydropneumatic suspension system — a hallmark of Citroën road cars — increased understeer in competitive conditions.
The BX 4TC made its WRC debut at the 1986 Monte Carlo Rally, where both entries retired due to mechanical breakage and going off-road. The car's best championship result came at the Rally of Sweden, where Jean-Claude Andruet brought a BX 4TC home in sixth position. At the Acropolis Rally, the car's final championship event, all three entered BX 4TCs retired. Citroën withdrew from the championship following accidents at the Rally of Portugal and the Tour de Corse that killed multiple spectators and co-drivers across the Group B field, events which prompted the FIA to ban the category entirely. Citroën had intended to continue development and improve the car, but the category's abolition ended any opportunity to do so. The car had entered the season carrying significant expectations rooted in Citroën's earlier successes with the DS in rallying.
The production BX 4TC was powered by a 2142 cc N9TE engine: a 16-valve inline-four with Bosch L-Jetronic fuel injection and a 7:1 compression ratio, producing 200 hp DIN (147 kW) at 5,250 rpm. The block was cast iron with an aluminium cylinder head, chain drive, dual overhead camshafts, and a Garrett turbocharger feeding through an air-to-air intercooler. The engine was mounted longitudinally, producing the pronounced front overhang characteristic of the car. This unit was originally designed by Simca for Chrysler and was also used in the Peugeot 505 Turbo, where it had demonstrated robustness and tuning potential. Drive was transmitted through a five-speed manual gearbox. Manufacturer figures claimed a top speed of 220 km/h and a 0–100 km/h time of 7.5 seconds; independent tests by Sport Auto recorded 211 km/h and 9.1 seconds.
The 200-unit production run required for homologation was completed by Heuliez, as was the case with the competition cars. However, only 86 of the road cars found buyers; Citroën destroyed the unsold examples. The production BX 4TC sold poorly, hampered by the rally car's failure to deliver results and a performance level that fell short of comparable road cars. Over time, the car's rarity, its distinctively Citroën character — including the signature hydropneumatic suspension and bold styling — and its brief motorsport history have elevated its desirability among collectors. Examples now trade for prices in the tens of thousands of euros.
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