Citroën BX 4TC (Group B)

Published on: Jan 18, 2016 @ 16:39
Originally Published in: 2014 (old website)
(C) Jay Auger (RGBS), Martyn Morgan Jones (MotorSport Magazine - 2009) - partial
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Citroën BX 4TC Evolution


Before 1986, French automaker Citroën was competing in Group B with their front-wheel drive Visa rally cars and later with the four-wheel drive Mille Pistes version. These were low power B-9 (under 1300 cc) and B-10 (under 1600 cc) entry-level cars aimed at their respective classes’ honours. However, Citroën soon wanted to compete for the overall win in the B-12 (2000 cc +) class and gain much publicity from the World Rally Championship (WRC).



In 1983, Citroën Compétitions, along with various engineering firms, started to devise BX-model based B/12-class rally cars which were developed alongside the various Visa RWD & 4×4 prototypes. Under the supervision of team boss Guy Verrier, five BX prototypes were built in total; all sporting different specifications and designs, but all using variations of Peugeot’s X5N2 engine.

The first prototype, built by Strakit, had a 310 BHP, 1996 cc transversely mounted 16-valve engine, Hewland gearbox, front-wheel drive and resembled the later BX Sport/GTI models. It was soon however sent back to the design table since Verrier wanted four-wheel drive (4WD). The second prototype was a Michel Mokrycki design featuring a longitudinal 2155 cc turbo engine, a Citroën SM gearbox, hydropneumatic suspension and four-wheel drive.

The third was a 4WD evolution of the first prototype and was known as the “BX 4×4 Strakit”. It featured an improved 16v “ROC” 2445 cc engine producing around 325 BHP. The car was built around a spaceframe (tubular) chassis, sporting conventional MacPherson strut suspension, and draped in a lightweight composite body resulting in a 1050 kg (2315 lb) weight. The car performed admirably until it retired in the 1983 Rallye des Mille Pistes with overheating problems.

The fourth BX 4×4 prototype featured a classic monocoque construction, a front-mounted, longitudinal, N9TE 2140 cc engine (as originally used in the Chrysler 180 model), turbocharged, and originally tuned to 405 BHP (later reduced to 380 BHP for better reliability). The car sported a very short rear overhang versus a quite long front overhang, making for an unique albeit unbalanced appearance. However, both radiator and oil cooler were in the rear trunk section to help balance weight bias. Built in conjunction with Mokrycki, it also sported Citroën’s famous hydropneumatic suspension to help deal with rough terrain. The fifth and final prototype basically was a narrower road car version of the fourth prototype, featuring a 200 BHP de-tuned engine.


The last two prototypes were confirmed by team boss Guy Verrier to be Citroën Competitions’ future top Group B contender; the former being the competition version and the latter being the client “serie-200” homologation road model. Verrier wanted to link the rally car to the road-going BX by incorporating as many in-house parts as possible. As before with the Visa, all chassis were built by Heuliez. From this came the BX 4TC Evolution in partnership with Mokrycki. Citroën’s competition department built the 20 Evolution models at its headquarters in Trappe, France, and homologation was granted on January 1, 1986.


Electing to follow a less ‘bespoke’ route placed the BX 4TC Evolution at a huge disadvantage. It ended up being a veritable myriad of PSA parts slapped together. With massive budgets, most of Citroën’s rivals had used a series of special components to produce raw, feral machines, built without compromise. Verrier, driven by an emotional attachment to Citroën and a modest budget, oversaw the creation of something more domesticated yet, conversely, more difficult to control.


Group B’s winning recipe was its technical freedom; it dispensed with the need for manufacturers to rely on existing production models. Verrier and his team failed to embrace the spirit and failed to exploit the loose regulations, sanctioning an outmoded concept which almost mirrored the original Audi quattro: the engine was positioned far in the nose of the car. Despite being dry-sumped, fuel-injected and turbocharged, it was based on an outdated 1970 Simca design with iron block, alloy head, a single overhead camshaft and just eight valves.


Although the 4TC Evolution looked every inch a Group B monster, those outrageously-styled panels hid a weight problem: essentially a monocoque construction, albeit with special tubular subframes, the BX 4TC weighed in at a hefty 1150 kg (2,535 lbs), well above the 960kg class minimum and a lot more than its closest opposition. And, due to the extra frontal length to accommodate the longitudinal engine, it became Group B’s Cyrano de Bergerac (for the French novelist portrayed with a huge nose).


Although cited as a Citroën SM unit, the gearbox, first seen in the DS, was an even older design. From the gearbox back, things became even more simplistic. All that linked the gearbox to the Peugeot 505 rear differential was a carbon-fibre driveshaft. The competition department was happy to send the car out to do battle without a centre differential, transfer box, or even a viscous coupling, despite the fact that this would make its front and rear axles fight against each other. On asphalt, that problem would be even more prominent. To assist the driver in his struggles, hyper-sensitive Citroën CX (DIRAVI) variable-assistance power steering was fitted.


The rather aggressive driving style needed to make due with these technical oversights pushed the hydropneumatic suspension to its limits and beyond. Thankfully, it performed more fluidly on loose surfaces, where the drivetrain’s inadequacies were somewhat masked, although the limited suspension travel – three inches less than the best of its rivals – would soon bring the car up short on rough terrain. Although highly criticised for his decisions, Guy Verrier (probably blinded by his commitment to the marque), still had hopes for the BX 4TC’s potential to win.


Two cars contested the first event on the 1986 WRC calendar, the Monte Carlo Rally. One was driven by Jean-Claude Andruet, who had won the 1977 Sanremo, the 1974 Tour de Corse and, more importantly, the 1973 Monte Carlo. Philippe Wambergue, a Citroën test driver who would later excel at rallycross and in Rally Raids, drove the other. Andruet threw down the gauntlet and recorded seventh and eighth fastest times before crashing out on stage six. Wambergue fared less well, retiring on stage one due to suspension failure.

Citroen 1986 MC.jpg

In the Swedish Rally, asphalt expert Andruet surprised onlookers with his snow and ice pace, finishing sixth overall, albeit well back of other Group B supercars and only edging out Kenneth Eriksson in a Group A Volkswagen Golf GTi 16v by a minute and a half. Wambergue, who wasn’t far behind Andruet in the standings, would be sidelined by a frozen oil pipe on stage 25 and was forced to retire.

Citroen 1986 Sweden.jpg

Following a lengthy three-event development break, three cars were entered for the Acropolis Rally. Andruet and Wambergue were joined by Maurice Chomat, who’d finished 10th on the ’83 Acropolis in a Citroën Visa Chrono, and had a number of good results in a Visa 1000 Pistes. Sadly, Andruet only made it as far as stage three when he was involved in an accident. This was a huge blow for the team as, prior to the crash, he’d been only five seconds behind Kalle Grundel’s leading RS200. He was even ahead of eventual winner Juha Kankkunen who was driving a 205 T16. Wambergue’s car didn’t even manage to complete the first stage due to suspension failure. Chomat, his car similarly afflicted, also called it a day.

Citroen 1986 Acropolis.jpg

After the rally’s bitter disappointments, Citroën pulled the BX 4TC out of the WRC on the spot. A brave yet misguided endeavour, the BX 4TC Evolution was hampered by a limited budget, umbilically tied to its road-going counterpart, a lack of technical development, and its late arrival. Had the car appeared two years earlier it would have stood a better chance of success. Worse still, by persisting with what was so obviously an outdated concept, 1985 proved to be a wasted year. The BX 4TC Evolution was immediately outclassed by a raft of space-framed and mid-engined supercars which proved to be as nimble as they were quick.


By this time, due to the safety concerns, Group B was ready to be banned at the end of the year which probably made Citroën’s decision easier. Yet, the abysmal results would always remain in the company’s history: the BX 4TC is often referred as the worst endeavour at creating a competitive Group B car. Citroën was reportedly so distraught about their humiliating and wasted efforts that it is rumoured they had most of the evolution rally cars disassembled (only 6/20 are currently accounted for today). Two of these cars had however already been purchased by privateers and entered into the French Rallycross series. Even though these particular BX 4TCs were used to good effect in the hands of drivers like Jean-Luc Pallier and Patrick Pivert, Citroën apparently put much pressure for the cars to ‘retire’ at the end of the 1989 season. Citroën would then find solace in relinquishing their BX 4TC to a hazy memory.


Group/Class B/12 Homologation Number: B-279 (click # to view papers)
Years active 1986 Homologation

  • start: January 1st 1986
  • end: December 31st 1990
Type Simca type 180 N9TE, I-4, OHC 8v, gas located front longitudinal with 15o right inclination
Displacement 2140 cc WRC x 1.4 = 2998 cc
Compression ratio 7.0:1
Output power – torque 380 HP @ 7000 rpm 340 lb-ft (460Nm) @ 5500 rpm
Materials block: cast iron cylinder head: aluminium
  • KKK K26 turbocharger
  • Electric compressor before turbocharger
  • air/air intercooler
  • Bosch K-jetronic multipoint mechanical fuel injection
Boost: 18 psi (1.25 bar)
Ignition electronic, firing order 1-3-4-2
Cooling system water-cooled 9.5 lt
Lubrication system dry sump with oil cooler located below rear spoiler
Type four-wheel drive Citroën type SM-C35 / 5 speed gearbox
Gearbox ratios
  • constant: 1.000
  • 1st: 2.923
  • 2nd: 1.941
  • 3rd: 1.321
  • 4th: 0.969
  • 5th: 0.756
  • R: 3.153
  • constant: 1.000
  • 1st: 2.500
  • 2nd: 1.777
  • 3rd: 1.381
  • 4th: 1.130
  • 5th: 0.96
  • R: 3.153
  • constant: 1.000
  • 1st: 3.307
  • 2nd: 2.250
  • 3rd: 1.631
  • 4th: 1.227
  • 5th: 0.96
  • R: 3.153
Differential ratio
  • 3.889
  • 4.375
  • 4.857
  • 4.875
spiral bevel gears 30% limited slip front differential. Hypoid spiral bevel gears 30% limited slip rear differential. Lock mechanism to rear differential engagement
Clutch dry – double plate
Type steel monocoque chassis with roll cage. 5 door hatchback steel bodyshell with fiber panels, bumpers, doors, bonnets and rear spoiler
Front suspension hydropneumatic suspension, double wishbones with 1 lower wishbone and 1 upper short transverse arm, and anti roll bar
Rear suspension hydropneumatic suspension, double wishbones with 1 lower wishbone and 1 upper short transverse arm, and anti roll bar
Steering system rack and pinion with hydraulic power assistance
  • 14.48:1 or
  • 11.16:1
Brakes front and rear ventilated rotors 260mm diameter with 4 aluminium piston calipers dual circuit with servo
length: 4590 mm (180.7 in) width: 1915 mm (75.4 in) height: 1380 mm (54.3 in)
wheelbase: 2612 mm (102.8 in) front track: 1550 mm (61.0 in) rear track: 1550 mm (61.0 in)
Rims – tires 150 TR 380FH 210/55×15 VR 390
Dry/Unladen Weight 1150 kg (2,535 lb)
Weight/power 3.0 kg/HP
Fuel tank 85 – 110 lt
Drag coefficient 0.38



Citroën BX 4TC – Serie 200

While work on the production model started in 1984, due to FISA leeway in the latter Group B years, the 20 evolution rally cars were officially homologated before the unlikely completion of the required amount of road cars. As such, production of the BX 4TC homologation model ended short of the required 200 units with only 105 cars reportedly manufactured when news of the cancellation of Group B was made. To further reduce production costs, the car shared many parts with the Peugeot 505. On paper, the Serie 200 was more than a match for the legendary Audi quattro. However, on the road, it was plagued by poor reliability, somewhat low performance, and high repair costs.


By 1988, due to its high price and bad reputation, only 85 of the 105 road cars had been reportedly sold. Sadly, the cars came to be seen as a blight and financial pit for Citroën. Thus, rather than honouring the warranties, Citroën decided to buy back as many examples as they could to have them stripped of their parts, ultimately destroying them in the process. It estimated that only about 30% of the cars produced still exist today. As such, the very few surviving BX 4TC Serie 200s are very coveted by today’s Citroën collectors but can be bought relatively cheaply as opposed to other Group B homologation specials.

Six evolution cars are known to have survived. Philippe Wambergue rebuilt his Acropolis car. Dominic, his brother, has Philippe’s Monte Carlo/Swedish Rally example. Another resides in Citroën’s heritage museum. The Hommel Museum has one, and the Garage du Midi has an ex-rallycross car. The last one was bought by Patrick Pivert, who competed in the French Rallycross Championship, from French rallycross ace Jean-Luc Pallier. The car was re-sold and is now domiciled in the UK.

Please visit this private BX 4TC registry for more information about the survivor cars.


Class Mid-Size Homologation Number: B-279 (click # to view papers)
Production 1984~86 (105) Assembly: France
Type I-4, 2.2L, OHC 8v, gas located front longitudinal with 15o right inclination
Engine Code N9TE
Output power – torque 200 HP @ 5250 rpm 217 lb-ft (294Nm) @ 2750 rpm
  • Garett turbocharger
  • electric compressor before turbocharger
  • air/air intercooler
Boost: N/A
Ignition electronic / firing order 1-3-4-2
Cooling system water-cooled
Lubrication system N/A
Type four-wheel drive Citroën Type SM 5 speed gearbox
Gearbox ratios
  • N/A
Differential ratio
  • N/A
spiral bevel gears 30% limited slip front differential. Hypoid spiral bevel gears 30% limited slip rear differential. Lock mechanism to rear differential engagement
Clutch N/A
Type steel monocoque chassis, 5 door hatchback type
Front suspension hydro-pneumatic suspension, double wishbones with 1 lower wishbone and 1 upper short transverse arm, and anti roll bar
Rear suspension hydro-pneumatic suspension, double wishbones with 1 lower wishbone and 1 upper short transverse arm, and anti roll bar
Steering system rack and pinion with hydraulic power assistance 2.5 turns lock to lock
Brakes Front and Rear vented rotors with 4 piston calipers
length: 4512 mm (177.6 in) width: 1830 mm (72.0 in) height: 1349 mm (53.1 in)
wheelbase: 2612 mm (102.8 in) front track: 1548 mm (60.9 in) rear track: 1548 mm (60.9 in)
Curb Weight 1280 kg (2815 lb)
Weight/power 6.4 kg/HP (14.1 lb/HP)
Fuel tank 83 litres
Drag coefficient 0.38


Bertone would design a concept car named the Zabrus which was based on the BX 4TC chassis and mechanicals.
In 1986, Bertone would design a concept car, the Zabrus, which was based on the BX 4TC’s chassis and mechanical components.

Please come back later for a dedicated article on the Zabrus!



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  • Partial source: (C) MotorSport Magazine – Sep 2009 issue (edited, abridged) – used under permission
  • Images & videos are the property of their original owners
  • All homologation papers are the property of the Fédération Internationale de l’Automobile (FIA): SOURCE
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