Ford Sierra RS Cosworth

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Ford Sierra RS Cosworth
ManufacturerFord Motor Company
Production30,932 (total):

5,042 (3d, 1986)
500 (RS500, 1987)
13,140 (4d, 1988-1989)

12,250 (4d 4WD 1990-1992)
Body style(s)3-door hatchback (1986-1987)
4-door notchback (1988-1992)
Layoutfront engine,

rear wheel drive (1986-1989)

four wheel drive (1990-1992)
Engine(s)Cosworth YBB, 204 hp (1986)

Cosworth YBD, 224 hp (1987)
Cosworth YBB, 204 hp (1988-1989)

Cosworth YBG/YBJ, 220 hp (1990-1992)

Borg Warner T5 (1986-1989)

Borg Warner MT75 (1990-1992)
Length446 cm (1986-1987)
449 cm (1988-1992)
Width173 cm (1986-1987)
170 cm (1988-1992)
Height138 cm (1986-1992)
Curb weight1217 kg (1986-1987)

1206 kg (1988-1989)

1305 kg (1990-1992)
RelatedFord Escort RS Cosworth
ManualsService Manual

Ford Sierra RS Cosworth is the result of a Ford-project with the purpose of "Producing a downright winner for Group A racing events in Europe."


The project was defined by Stuart Turner in the spring of 1983. He had then recently been appointed head of Ford Motorsport in Europe, and he realized right away that Ford was no longer competitive in this area.

Turner got in touch with Walter Hayes, at the time Vice President of Public Relations at Ford, to get support for the project. Hayes had earlier been the driving force behind the development of the Ford GT40 that won Le Mans in 1966, and the Cosworth DFV engine that brought Ford 154 victories and 12 World Championships in Formula One during the Sixties and Seventies. Hayes found the project very appealing and promised his full support.

Turner then invited Ken Kohrs, Vice President of Development, to visit Ford’s long time partner, the automotive company Cosworth, where they were presented a project developed on Cosworth’s own initiative, the YAA engine. This was twin cam, 16-valve engine based on Ford’s own T88 engine block, better known as the Pinto. This prototype proved an almost ideal basis for the engine Turner needed to power his Group A winner.

Therefore, an official request for a turbocharged version (designated Cosworth YBB) capable of 180 HP on the street and 300 HP in race trim, was placed. Cosworth answered positively, but they put up two conditions: the engine would produce not less than 150 kW (204 HP) in the street version, and Ford had to accept no less than 15,000 engines. Turner’s project would only need about 5,000 engines, but Ford nevertheless accepted the conditions. The extra 10,000 engines would later become one of the reasons Ford also chose to develop a four door, second generation Sierra RS Cosworth.

To find a suitable gear box proved more challenging. The Borg-Warner T5, also used in the Ford Mustang, was chosen, but the higher revving nature of the Sierra caused some problems. Eventually Borg-Warner had to set up a dedicated production line for the gear boxes to be used in the Sierra RS Cosworth.

In April 1983, Turner’s team decided on the Sierra as a basis for their project. Sierra filled the requirements for rear wheel drive and decent aerodynamic drag. A racing version could also help to improve the unfortunate, and somewhat undeserved, reputation that Sierra had earned since the introduction in 1982.

Lothar Pinske, responsible for the car’s bodywork, demanded carte blanche when it came to appearance in order to make the car stable at high speed. Experience had shown that the Sierra hatchback body generated significant aerodynamic lift even at relatively moderate speed.

After extensive wind tunnel testing and test runs at the Nardò circuit in Italy, a prototype was presented to the project management. This was based on an XR4i body with provisional body modifications in fibreglass and aluminium. The car’s appearance raised little enthusiasm. The large rear wing caused particular reluctance. Pinske insisted however that the modifications were necessary to make the project successful. The rear wing was essential to retain ground contact at 300 km/h, the opening between the headlights was needed to feed air to the intercooler and the wheel arch extensions had to be there to house wheels 10” wide on the racing version. Eventually, the Ford designers agreed to try and make a production version based on the prototype.

In 1984 Walter Hayes paid visits to many European Ford dealers in order to survey the sales potential for the Sierra RS Cosworth. A requirement for participation in Group A was that 5,000 cars were built and sold. The feedback was depressing. The dealers estimated they could sell approximately 1,500 cars.

Hayes didn’t give up however, and continued his passionate internal marketing of the project. As prototypes started to emerge, dealers were invited to test drive sessions, and this increased the enthusiasm for the new car. In addition, Ford took some radical measures to reduce the price on the car. As an example, the car was only offered in three exterior colours (black, white and moonstone blue) and one interior colour (grey). There were also just two equipment options: with or without central locking and electric window lifts.


Ford Sierra RS Cosworth was first presented to the public on the Geneva Motor Show in March 1985, with plans to release it for sale in September and closing production of the 5,000 cars in the summer of 1986.

In practice, it was launched in July 1986 and 5545 were manufactured in total of which 500 were sent to Tickford for conversion to the Sierra 3 door RS500 Cosworth. The vehicle was manufactured in both RHD (Right Hand Drive) for the UK market, and LHD (Left Hand Drive) for Europe. The following number of vehicles were registered in the UK:

1985 10
1986 1064
1987 579
Total 1653

Sierra RS500 Cosworth

Mike Moreton was head of the team that planned to develop an evolution edition aimed at making the car unbeatable on the race tracks. In March 1987, Aston Martin in Tickford was signed for the job of converting the 500 cars.

The Cosworth RS500 was announced in July 1987 and was homologated in August 1987.

The main difference to the Sierra 3 door Cosworth was the uprated Cosworth competition engine. Its new features were:

  • The engine had a thick walled cylinder block to cope with the rigours of the track.
  • A larger turbocharger and intercooler was fitted.
  • A second set of 4 unused injectors were added to the fuel system and the fuel pump was uprated.
  • The oil and cooling system were both also uprated.
  • The rear semi-trailing arm beam had extended but unused mounting points.

The RS500 also had minor external cosmetic differences to its parent the Sierra 3 door Cosworth:

  • The rear tail gate had a lower spoiler in additional to the upper whale tail, which had an added lip.
  • Discrete RS500 badges on the rear tail gate and front wings.
  • A redesigned front bumper and spoiler to aid cooling and air flow.
  • The bonnet louvre air vents were of a slightly different design.

Exactly 500 RS500s were produced, all left hand drive.

Motorsport achievements

The car also fulfilled Ford's expectations on the race track. When the FIA arranged a World Touring Car Championship in 1987, it came like a gift to Ford. Competent BMW drivers, some trouble with gear boxes, amongst other things, and only 340 HP in the first Sierra RS Cosworth prevented Ford from dominating the first half of the season.

In August 1987 however, the Sierra RS500 Cosworth was homologated. Ford took pole position in all the remaining six events, and was first over the finishing line in five of them. The dominance proved so overwhelming, no World Championship was arranged in the following years.

"The Executive Express"

Even before the first generation Sierra RS Cosworth was in production, Ford started to investigate the possibilities of using the technical solutions in the second generation Ford Sierra as well.

Sierra RS Cosworth 4x4

Ford Sierra RS Cosworth 4x4.

In January 1990 the third generation Sierra RS Cosworth was launched, this time with four wheel drive. As early as 1987, Mike Moreton and Ford Motorsport had been talking about a four wheel drive Sierra RS Cosworth that could make Ford competitive in the World Rally Championship. The Borg Warner T75 gear box that was considered an essential part of the project wasn’t available until late 1989 however.

Ford Motorsport’s desire for a 3-door “Motorsport Special” equivalent to the original Sierra RS Cosworth was not embraced. The more discreet 4-door version was considered to have a better market potential. It was therefore decided that the new car should be a natural development of the second generation, to be launched in conjunction with the face lift scheduled for the entire Sierra line in 1990.

The waiting time gave Ford Motorsport a good opportunity to conduct extensive testing and demand improvements. One example was the return of the bonnet louvers. According to Ford’s own publicity material, 80% of the engine parts were also modified. The improved engine was designated YBJ for cars without a catalyst and YBG for cars with a catalyst. The latter had the red valve cover replaced by a green one, to emphasize the environmental friendliness. Four wheel drive and an increasing amount of equipment had raised the weight by 100 kg, and the power was therefore increased to just about compensate for this.

Sierra RS Cosworth 4x4 received, if possible, an even more flattering response than its predecessors and production continued until the end of 1992, when the Ford Sierra was replaced by the Ford Mondeo. The replacement for the Sierra RS Cosworth was not a Mondeo however, but the Escort RS Cosworth. This was to some extent a Sierra RS Cosworth clad in an “Escort-like” body. The car was released in May 1992, and was homologated for Group A rally in December, just as the Sierra RS Cosworth was retired.