Ford Sierra RS Cosworth
| Ford Sierra RS Cosworth | |
|---|---|
 | |
| Overview | |
| Manufacturer | Ford Europe |
| Production | 1986–1992 |
| Body and chassis | |
| Body style |
3-door hatchback (1986-1987) |
| Layout |
front engine, |
| Related | Ford Escort RS Cosworth |
| Powertrain | |
| Engine |
Cosworth YBD, 204 hp (1986) |
| Transmission |
5-speed |
| Dimensions | |
| Length |
446 cm (1986-1987) |
| Width |
173 cm (1986-1987) |
| Height | 138 cm (1986-1992) |
| Curb weight |
1217 kg (1986-1987) |
The Ford Sierra RS Cosworth is a high-performance version of the Ford Sierra that was built by Ford Europe from 1986 to 1992. It was the result of a Ford Motorsport project with the purpose of producing an outright winner for Group A racing in Europe.[1]
Development
The project was defined by Stuart Turner in the spring of 1983. He had recently been appointed head of Ford Motorsport in Europe, and he realised right away that Ford was no longer competitive in this area.
Turner got in touch with Walter Hayes, at the time the 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 a 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 fewer 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 gearbox 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 gearboxes 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 not encouraging. The dealers estimated they could sell approximately 1,500 cars.
Hayes did not 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.
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 three-door RS500 Cosworth. The vehicles were manufactured in right hand drive (RHD) only, and were made in Ford's Genk factory in Belgium. The following number of vehicles were registered in the UK:
| 1985 | 10 |
| 1986 | 1064 |
| 1987 | 579 |
| Total | 1653 |
As published in the 1986 RS catalog:
- Max Speed: 149 mph
- 0-60 mph: 6.5 sec
- Fuel Consumption at 56 mph: 38.2 mpg
- Fuel Consumption at 75 mph: 30.1 mpg
- Drag Coefficient: 0.345
- Rear Spoiler: 20kgf at 150mph
- Front Brakes: Disc 28.3 cm diameter
- Rear Brakes: Disc 27.3 cm diameter
- Differential: Viscous Coupled limited slip
- Tyre Size: 205/50 VRx15
- Wheels: 15"x7" Alloys
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 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 three-door Cosworth was the uprated Cosworth competition engine. Its new features were:[2]
- The engine had a thicker walled cylinder block to cope with the rigours of the track
- A larger Garrett T04 turbocharger
- A larger air-air intercooler
- A second set of four fuel injectors and a second fuel rail (unused in the roadgoing version)
- An uprated fuel pump
- A reworked induction system to allow higher power outputs to be realised
- An uprated oil and cooling system
- 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 three-door Cosworth:
- The rear tail gate had a lower spoiler in addition to the upper "whale tail", which had an added lip
- Discreet 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 .[1]
Motorsport achievements
Touring car racing
The car also fulfilled Ford's expectations on the race track. The 1987 World Touring Car Championship came like a gift to Ford. Class BMW Motorsport drivers, trouble with gearboxes and small turbos that were prone to failure, amongst other things (including weak axles and differentials), and only 370 hp (276 kW; 375 PS)[3] in the first Sierra RS Cosworth prevented Ford from dominating the first half of the season.
In August 1987, the Sierra RS500 Cosworth was homologated with larger turbos and a new rear deck spoiler, plus the added bonus of an extra 100+ HP. Fords took pole position in all the remaining six events, and was first over the finish line in four of them. Disqualification of the works Eggenberger Motorsport cars from the 1987 James Hardie 1000 in Australia for wheel arch panel irregularities was a bitter pill for the Fords, depriving West German pair Klaus Ludwig and Klaus Niedzwiedz of the world championship and handing it to Schnitzer BMW's Italian driver, Roberto Ravaglia. The pill was harder to swallow since the Texaco RS500 Sierras ran in the same configuration at five of the last six WTCC races, but were only protested against at Bathurst (Eggenberger modified the wheel arches to make them legal for the final race of the championship, the InterTEC 500 at the Fuji Speedway in Japan). The Eggenberger Motorsport team did however claim the entrants' prize.[4]
The RS500 was highly successful in Australian touring car racing with Dick Johnson Racing dominating the 1988 and 1989 Australian Touring Car Championships, with team boss Dick Johnson and his team mate John Bowe finishing one-two in both years (Sierra's would take the top three in the championship in both years). Early in 1988, the Johnson team also took the step of homologating a modified Ford nine-inch axle for the Sierra, eliminating one of the cars biggest weaknesses (its weak drivetrain) and allowing the cars to be driven harder with less fear of failure. This was also seen as essential in Australia which used standing starts compared to the rolling starts used in Europe.
Johnson and Bowe also won the 1989 Tooheys 1000 at Bathurst, while Tony Longhurst and Tomas Mezera had won the 1988 Tooheys 1000 in an RS500. Allan Moffat and Gregg Hansford also drove an Eggenberger built RS500 to victory in the 1988 Sandown 500 in what was Moffat's last win on Australian soil. Stiff competition from Nissan, first with the Nissan Skyline HR31 GTS-R and then the 4WD twin-turbocharged Nissan GT-R, a revitalised BMW M3 Evolution with upgraded aerodynamics and a larger displacement (up from 2.3L to 2.5L), and to a lesser extent the V8 powered Holden Commodore SS Group A (both the VL and later VN models), saw the ageing Sierras largely outpaced in the 1991 ATCC as teams continued to struggle with putting the in excess of 590 hp (440 kW; 598 PS) through its relatively skinny rear tyres. However, following a change in regulations for the last year of Group A racing in Australia in 1992 (a rev limit of 7,500 for the Sierra and Commodore, plus pop-off valve and weight restrictions to the 630 hp (470 kW; 639 PS) GT-R's), the Sierras were back on the pace and winning races and in some cases were in fact faster than they had been previously.
The Sierra RS500 claimed pole for the Bathurst 1000 five times in its six years of competition at the 6.213 km (3.861 mi) Mount Panorama Circuit. The poles won were in 1987 (Ludwig), 1988 (Johnson), 1989 (Peter Brock), 1990 (Niedzwiedz) and 1992 (Johnson). The only non-Sierra pole at Bathurst was by the Nissan GT-R of Mark Skaife in 1991, which was also the only year no Sierra qualified on the front row as the GT-R of Mark Gibbs qualified second with the fastest Sierra (Glenn Seton) in third. The Holden VL Commodore SS Group A SV of Larry Perkins claimed the only other non-Sierra front row start at Bathurst between 1987 and 1992 when he qualified second alongside Johnson's Sierra in 1992.
Along with the BMW M3, the Cosworth Sierras were the first Group A touring cars that were not road cars that had been put into use as race cars. Both Ford and BMW designed their cars as race cars, which under Group A rules needed to be put into production as road cars. All other leading Group A contenders up to 1987 (Jaguar XJS, Holden Commodore, BMW 635 CSi, Mitsubishi Starion, Rover Vitesse, Ford Mustang, Nissan Skyline DR30 RS and Skyline HR31 GTS-R and the Volvo 240T) were road cars first that later found a home in touring car racing.
Rallying
The Sierra Cosworth was also pressed into service as a rally car, and saw some success. After the abolition of the Group B formula in the World Rally Championship at the end of 1986, manufacturers had to turn to Group A cars and Ford, like most others, found itself without a fully suitable car. The Cosworth was very powerful but, with only rear-wheel-drive, lost out to the four-wheel-drive Lancias and Mazdas on loose-surface events, while the four-wheel-drive XR4x4 had an excellent chassis but an elderly engine producing only around 200 bhp, at least 100 less than the Lancia. For the 1987 season the team ran both, using the XR4x4 on loose surfaces and the Cosworth on tarmac, but the XR4x4's power disadvantage was too great and from 1988 the team concentrated on the Cosworth alone, and continued to use it until the arrival of the Sierra RS Cosworth 4x4 in 1990.
The rear-drive car never won a loose-surface World Rally Championship event, but in the hands of drivers such as Stig Blomqvist, Carlos Sainz and Ari Vatanen it frequently finished in the top five, except when conditions were particularly slippery. On tarmac it was a much more serious competitor, and a young Didier Auriol won the 1988 Corsica Rally outright, the only time that season that Lancia were beaten in a straight fight. However, as Lancia developed the Delta Integrale further and new cars such as the Toyota Celica GT-Four ST165 appeared, the Cosworth became steadily less competitive.
Thanks to strong support and readily available parts from Ford Motorsport, the Cosworth was a popular car with private teams. Moreover, below world championship level, four-wheel-drive opposition was limited at the time, and the Cosworth was as fast as any of its two-wheel-drive rivals. It lacked the fine handling of the BMW M3, for example, but on the other hand it was much more powerful. It was also very reliable. Consequently it became a very popular car at national championship level, and during the late 1980s Sierra drivers won many national series. Jimmy McRae took the British Rally Championship in a Sierra in 1987 and 1988, whilst Carlos Sainz won the Spanish Championship in the same years, to name but two. The Cosworth was popular with spectators because it was visually dramatic, with its flame-spitting exhaust and tail-sliding, rear-drive handling; and it was popular with amateur drivers because it was competitive, robust and relatively cheap. To this day it is a fairly common sight on lower-level events.
WRC victories
No. Event Season Driver Co-driver Car 1 
32ème Tour de Corse1988 Didier Auriol Bernard OccelliFord Sierra RS Cosworth
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[5] 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.
The Sapphire Cosworth, being based on a different shell to the original three-door Cosworth, along with its more discreet rear wing, recorded a drag co-efficient of 0.33, thus allowing it to register slightly better performance figures (top speed of 150 mph and 0-60 of 6.1 seconds) compared to the original Cosworth.
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 Ferguson MT75 gearbox 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 went on sale in May 1992, more than a year after the first pre-production examples were shown to the public, and was homologated for Group A rally in December, just as the Sierra RS Cosworth was retired. It continued in production until 1996.
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.
References
- 1 2 Moreton, Mike (October 2007). Rallye Sport Fords - the inside story. Veloce Publishing Ltd. ISBN 978-1-84584-115-7.
- ↑ Pitt, Colin (2006). The Ford Sierra RS Cosworth. C P Press. ISBN 978-1-84155-666-6.
- ↑ 1987 WTCC Cars index
- ↑ Autosport, January 14, 1988
- ↑ "RSOC : Car Cars : Capri RS Zazspeed Turbo". rsownersclub.co.uk.
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