Sierra RS Cosworth

  1986 to 1992

Manufacturer	Ford Motor Company
Production	30,932 (total): 5,042 (3d, 1986) 500 (RS500, 1987) 13,140 (4d 2wd, 1988-1989) 12,250 (4d 4WD 1990-1992)
Body style	3-door hatchback (1986-1987) 4-door notchback (1988-1992)
Layout	front engine, rear wheel drive (1986-1989) four wheel drive (1990-1992)
Engine	Cosworth YBB, 204 hp (1986) Cosworth YBD, 224 hp (1987) Cosworth YBB, 204 hp (1988-1989) Cosworth YBG/YBJ, 220 hp (1990-1992)
Transmission	5-speed Borg Warner T5 (1986-1989) Borg Warner MT75 (1990-1992)
Length	446 cm (1986-1987) 449 cm (1988-1992)
Width	173 cm (1986-1987) 170 cm (1988-1992)
Height	138 cm (1986-1992)
Curb weight	1217 kg (1986-1987) 1206 kg (1988-1989) 1305 kg (1990-1992)

The Ford Sierra RS Cosworth was a high-performance version of the Ford Sierra. It was the result of a Ford Motorsport project with the purpose of producing an outright winner for Group A racing in Europe.

History

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 1960s and 1970s. Hayes found the project very appealing and promised his full support.

Turner then invited Ken Kohrs, Vice President of Development, to visit Ford’s longtime 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.

Many of the suspension differences between the standard Sierra and the Cosworth attributed their development to what was learned from racing the turbocharged Jack Roush IMSA Merkur XR4Ti in America and Andy Rouse's successful campaign of the 1985 British Saloon Car Championship. Much of Ford's external documentation for customer race preparation indicated "developed for the XR4Ti" when describing parts that were Sierra Cosworth specific. Roush's suspension and aerodynamics engineering for the IMSA cars was excellent feedback for Ford. Some production parts from the XR4Ti made their way into the Cosworth such as the speedometer with integral boost gauge and the motorsport 909 chassis stiffening plates.

In April 1983, Turner’s team decided on the Sierra as a basis for their project. The 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 to 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.

Race Versions

The racing version, unlike the road version and according to the regulations in force at the time in force in Group A, did not differ significantly. It had been lightened, reaching 1035 kg and the engine boosted to 370; while the RS500, thought 1040 and delivered 470 hp. It was mainly used in the ETCC and WTCC championships.

In August 1987 the Sierra RS500 Cosworth was homologated with a larger turbo, a new rear spoiler and an extra 100 horsepower. Ford took pole position in six events of the 1987 World Touring Car Championship, winning four. The car was disqualified at the 1987 Bathurst 1000 in Australia for irregularities in the wheel arch panel, depriving Klaus Ludwig and Klaus Niedzwiedz of world championship victory. With the Eggenberger Motorsport team the car won the 1989 24 Hours of Spa. Robb Gravett won the British Touring Car Championship in 1990 on a Sierra RS500.

The RS500 was successful in the 1988 DTM with Klaus Ludwig winning the drivers' championship and Wolf Racing the team one. Also in Australian racing, with Dick Johnson Racing, he dominated the 1988 and 1989 Australian Touring Championships, with Dick Johnson and John Bowe finishing first and second in both years. Glenn Seton won the Australian Endurance Championship in 1990 driving a Sierra RS500.

The RS500 won the Bathurst 1000 twice: in 1988 with Tony Longhurst and Tomas Mezera and in 1989 with Johnson and Bowe; the Sandown 500 of 1988 with Allan Moffat and Gregg Hansford and the Sandown 500 of 1990 with Glenn Seton and George Fury . Robbie Francevic graduated as the winner of the New Zealand Touring Championship in 1989 and 1990 with the Mark Petch Motorsport team.

The Sierra Cosworth was also used in rallies. After the abolition of Group B in the World Rally Championship at the end of 1986, the manufacturers had to use Group A cars and Ford, like most of them, found itself without a suitable car for that purpose.

The RS200 was therefore retired, no longer in line with the new regulations and it was decided to deploy the Sierra, in the XR4x4 versions and later with the Cosworth. The Sierra Cosworth thanks to its more powerful engine had the advantage on the asphalt, but with the rear-wheel drive alone, it was not competitive enough compared to the four-wheel drive Lancia and Mazda on dirt roads or snow, while the four-wheel Sierra XR4x4 tractors had an old-fashioned engine that produced about 200 hp, on average 100 hp less than the Lancias. For the 1987 season Ford ran with both, using the XR4x4 on low-grip surfaces and the Cosworth on asphalt, but the power handicap of the XR4x4 was too clear and from 1988 Ford only used the Cosworth. In 1990 the Sierra RS Cosworth 4x4 was introduced,

The rear-wheel drive Sierra Cosworth won only one World Rally Championship event, scoring only modest finishes with Stig Blomqvist, Carlos Sainz  and Ari Vatanen at the wheel, making it to the top of the top five. Only Didier Auriol managed to win a world event, the 1988 Rally of Corsica. Between 1987 and 1992, Sierra's balance in the world rally was 14 podiums, a second place and the title of second world constructors' champion in 1988 and third in the 1992 constructors' championship.

In the national championships during the late 1980s, Jimmy McRae won the British Rally Championship aboard a Sierra in 1987 and 1988, while Carlos Sainz won the Spanish championship in the same years.

Production

The Ford Sierra RS Cosworth was first presented to the public at 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 were manufactured in RHD (Right Hand Drive)only. The following number of vehicles were registered in the UK:1985-10,1986-1064,1987-579 in Total=1653

Engine

Based on the 2.0-liter engine with overhead camshaft developed by Ford for the Pinto , Cosworth first developed a 16V cylinder head with two overhead camshafts on its own. Ford took over the cylinder head in view of the motorsport activities with the Ford Sierra in the rally world championship and in various touring car championships. After the engine for the homologation model Sierra RS Cosworth with Garrett T3 turbocharger(Type YBB, red valve cover) followed by the Sierra RS500, which was revised again for motorsport purposes and limited to 500 pieces. This vehicle was converted by Tickford in Great Britain and was only available as a right-hand drive (type YBD, red valve cover). With the second model generation, the Sierra RS Cosworth was only available as a notchback sedan, the version with rear-wheel drive without catalytic converter was also equipped with the YBB , the all-wheel drive version with catalytic converter and lambda control was delivered with slight modifications to the engine (YBG, green valve cover).

The Escort RS Cosworth was initially also delivered with the YBG des Sierras (but with a blue valve cover), later versions received a further revised engine (YBP, gray valve cover) with the smaller T25 turbocharger from Garrett, also known as HTT-Cosworth . The "HTT" stands for high torque turbowhat turbo means with high torque. The smaller charger improved the response and the torque was already available at lower speeds. The YBP was the only Cosworth to be equipped with a Ford injection system and dual spark ignition; the remaining engines were all equipped with a Weber-Marelli engine control system and a contactless ignition distributor. The standard models without a catalytic converter had an output of 150 kW (204 hp), the vehicles with a catalytic converter and lambda control 162 kW (220 hp), and in motorsport, outputs of over 368 kW (500 hp) were achieved in the 80s and 90s.

The vehicles used by the manufacturer were only moderately successful in the World Rally Championship, with the Sierra Cosworth 4x4 and Sierra RS500, however, countless race victories and national and international championships were achieved in round and long-distance races. The engine's greatest successes were the championship title in the DTM in 1988 by Klaus Ludwig as well as the runner-up title in 1987 by Manuel Reuter and in 1989 by Klaus Niedzwiedz . In the BTCC , Andy Rouse won the championship title in 1985 and Rob Gravett in 1990. At the 24-hour race on the NürburgringKlaus Ludwig, Klaus Niedzwiedz and Steve Soper achieved a start-to-finish victory on a Sierra Cosworth in 1987. With the Escort RS Cosworth was François Delecour in the 1993 World Rally Championship runner-up, Carlos Sainz finished in 1996 and 1997 respectively the third place in the championship standings.

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

• The rear tail gate had a lower spoiler in addition 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, including the removal of the fog lamps and their replacement with intake grilles to supplement brake cooling

Exactly 500 RS500s were produced, all of them RHD for sale in the UK only - the biggest market for this kind of Ford car. It was originally intended that all 500 would be black, but in practice 56 white and 52 Moonstone Blue cars were produced

 2wd Sierra Sapphire RS Cosworth

The second generation 4 door Sierra Sapphire Cosworth was assembled in Genk, Belgium, with the UK-built Ford-Cosworth YBB engine. Cylinder heads on this car were early spec 2wd heads and also the "later" 2wd head which had some improvements which made their way to the 4X4 head. Suspension was essentially the same with some minor changes in geometry to suit a less aggressive driving style and favour ride over handling. Spindles, wheel offset and other changes were responsible for this effect. Approximately 13,140 examples were produced during 1988-1989 and were the most numerous and lightest of all Sierra Cosworth models. Specifically the LHD models which saved weight with a lesser trim level such as roll up rear windows, no air conditioning etc.

In the UK, the RHD 1988-1989 Sierra Sapphire RS Cosworth is badged as such with a small "Sapphire" badge on the rear door window trims. All 1988-1989 LHD models are badged and registered as a Sierra RS Cosworth with no Sapphire nomenclature at all. "Sapphire" being viewed as a Ghia trim level that saw power rear windows, air conditioning and other minor options. Enthusiasts of the marque are mindful of this and will describe the LHD cars by their body shell configuration, 3 door or 4 door. Example: 4 door Sierra RS Cosworth.

Wheeler Dealers Series sierra cosworth from series 7

Sierra RS Cosworth 4×4

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.

The 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 Sierra was replaced by the 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.

The 4x4 Cosworth made a few appearances as a works rally car in 1990, and then tackled a full World Championship programme for 1991 and 1992. It was not a great success and never won a World Championship event, although in the hands of drivers such as Francois Delecour and Massimo Biasion it did take several second and third places. Initially it was unreliable, the gearbox being an especially weak point, and although by 1992 the reliability problems had been solved the Cosworth was never quite as effective in most conditions as some of its rivals. It was a relatively large car, slightly heavy, and less sophisticated than the latter generations of the Lancia Delta and Toyota Celica in terms of transmission systems and electronics. Biasion was reputedly strongly critical of the car on his first events for the team in 1992, but earned its best World Championship finish on that year's Rally of Portugal, where he finished second. He also brought its World Championship career to a close with fifth place on that Lombard RAC Rally. By then technical development of the Sierra had ceased, and most of the team's effort was directed towards the upcoming Escort Cosworth, which promised to be a much more competitive prospect.

Like the rear-drive car, the Cosworth 4x4 was popular at lower levels of rallying and a consistent winner at national championship level, and it remains a popular car among amateur rally drivers.