Ford Escort RS Cosworth: the RALLY CAR

In the late eighties, Ford had reacted too late for Group B, had been unable of setting up the 4×4 Escort 1.7 Turbo and had never got enough power out of the Sierra RS Cosworth to seriously attempt to win in the World Rally Championship. The reaction to such list of deceptions came from a crazy but brilliant idea Stuart Turner conceived in 1988, in the form of shortening the platform of a Sierra Cosworth 4×4 and trying to fit the body of an Escort on it, powered by the exceptional Cosworth engine. John Wheeler and Mike Moreton prepared such a prototype, which was refined in Boreham, with the aid of Stig Blomqvist. The car was tested by multiple drivers, as well as by some key Ford decision makers, which helped a lot to convince Ford Management to invest in the project in 1989.

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F.Delecour/D.Grataloup, Ford Escort RS Cosworth, 1993 Rally of Portugal, 1st

The design of the new car, coded since then as project ACE-14, or simply ACE, was assigned to a external company, MGA Development from Coventry, where a team led by Steve Harper tried to follow the instructions from John Wheeler to build a sharp-edged and aerodynamic rally car and, at the same time, trying to satisfy Ford Europe’s desire to have a rounded, soft shape road car.

The first complete prototype was finished during Christmas 1989, and it was presented to press in early January 1990.

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First prototype presented to press, January 1990

A front splitter and rear wing were already present in this prototype, same design as it would be used in the next years in competition. Also, side skirts could be seen already at this previous stage. Under the front splitter, the spoiler could be extended, to increase splitter efficiency, or remain in a retracted position, as shown in the picture below from Homologation form.

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Car debut in a race was programmed in a short and free of homologation restrictions gravel rally, the 1990 Rally Talavera in Southern Spain, in order to avoid bad publicity in case of failure. But the car outperformed expectations and Mia Bardolet led it to the first victory of what it was going to be an impressive performance in the 90s decade.

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JM.Bardolet/A. Rodriguez, Ford Escort RS Cosworth, Rally Talavera, 1990, 1st

Car tests were developed all over 1991 and 1992 to better prepare the assault to the World Rally Championship. Once FIA homologated the car (see Homologation Form here), official debut took place in 1993 Rally of Montecarlo, where François Delecour finished second despite leading with a one minute advantage before the last night, due to reported engine problems in the Turini stages.

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F.Delecour/D.Grataloup, Ford Escort RS Cosworth, Rally Montecarlo, 1993, 2nd

But he succeeded to win in Portugal, Tour de Corse and Catalonia that year, while Miki Biasion won in Acropolis and Franco Cunico in Sanremo, completing a very successful first season of the new car.

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M.Biasion/T.Siviero, Ford Escort RS Cosworth, 1993 Tour de Corse Rally, 7th

However, 1993 Manufacturers title escaped to Ford, due to a great performance from Toyota drivers Juha Kankkunen and Didier Auriol.

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F.Delecour/D.Grataloup, Ford Escort RS Cosworth, 1993 Acropolis Rally, ret.

1994 season seemed to start at the same pace, as Delecour finally got the victory on his home roads of Montecarlo.

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F.Delecour/D.Grataloup, Ford Escort RS Cosworth, 1994 Montecarlo Rally, 1st

But a sudden loss of reliability, the reduction of Ford budget for the rally program and a road accident that left Delecour out for four races, resulted in poorer results for the rest of the season, with the only exception of the win raising star Tommi Makinen was able to obtain in Finland, in what it became first success of a brilliant career. Even so, the car obtained an impressive number of victories at European and national rallies and championships in 1994 and the following years, by what it is recognized as one of the most successful rally cars ever.

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T.Makinen/S.Harjanne, Ford Escort RS Cosworth, 1994 1000 Lakes Rally, 1st

Ford continued to participate in the World Championship with the Escort RS Cosworth in 1995 with no remarkable success. For 1996, the incorporation of an experienced driver such as Carlos Sainz didn’t change the trend, although the Spaniard got the last win for the Escort RS Cosworth in the World Championship at the Rally of Indonesia. After that, change of FIA regulations for 1997 forced Ford to introduce the new version of the car, the Escort WRC.

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C.Sainz/L.Moya, Ford Escort RS Cosworth, 1996 Rally Indonesia, 1st

A detailed description of the design process has been reported by Steve Harper, in what it is a unique opportunity to know how it was designed, with the aid of foam and clay:

John Wheeler wanted a huge cooling capacity for the car, as at ‘’100mph sideways in the dust of the Acropolis Rally, it gets pretty hot under the bonnet’’.  Therefore plenty of intakes and outlets were designed in, along with the bonnet bulge for the N-S engine. Plus there was John’s ‘patent’ cut away corners of the front bumper (in order to create controlled air flow and increase downforce)

The rear wing ‘element’ especially, was seen to be a critical part of the design, as John Wheeler had always rated the effectiveness of the ‘whale tail’ rear spoiler on the early rear wheel drive Sierra and the RS 500.  It had provided around 70-80kg of downforce at 100mph.  For the Escort, he felt 40-50kg would be sufficient, but he wanted to have downforce both front and rear, so the angle of the wing would be critical, to give the best drag/downforce compromise, and with normal front end lift, this then would require major aero detailing and refinement.

Dieter Hahne at Ford Motorsport had provided me with the necessary ‘developed’ wing profiles, which were collected by Peter Horbury on one of his Project discussion visits to Köln. 

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1989 Wind tunnel tests at MGA

 The aeromodel took about 7 weeks to build, and on we shipped it over to Ford’s own studio wind tunnel at the Merkenich design site in Köln.

Paternity of wing design is also claimed by young designer Frank Stephenson from Ford team in Germany, who got the inspiration from First World War Fokker DR1. His initial design included a tri-plane rear wing, but at the end was reduced to a bi-plane due to excessive cost. In any case, the influence of Sierra’s whale tail on Escort wing is undeniable.

Once back in Coventry, the relative wing positions etc were measured, ready to be developed as ‘styled’ parts on the full-size clay model.  Once all the data was secured, we then, in parallel to the clay model, started to develop the aeromodel further for the next set of wind tunnel-tests.

And the result was the impressive rear wing which contributed, together with a front splitter adjustable to 3 positions, to the first mass production car to produce downforce both at the front (up to 45N) and rear (up to 190N), as the company publicised the new Escort. Introduction of new rear wing resulted in an increase in drag coefficient from 0.34 for standard Escort to 0.38, which means that the gain in downforce was penalized with a loss in drag, that is, a lower top speed.

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Comparison of the rear wing between Sierra RS Cosworth and Escort RS Cosworth shows that Sierra’s was located half-way up the rear windscreen, while Escort’s is located at roof height, and lower wing is more prominent in the Escort.

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Both rear wings were designed to give more stability at car rear. In the case of Escort, it always performed very well on asphalt, but not in slippery rallies, although it has been reported to be related to a too conservative transmission design rather than to aerodynamics.

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After Ford, it was time for Japanese manufacturers to fly over the Championship. And Toyota was first to put Japan on top of the WRC.

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