The homologation of a group A car, until 1996, was a long and expensive process, as the production of 2500 cars was required. The FIA, in an attempt at reducing costs and bringing more manufacturers into the World Rally Championship, decided to simplify the homologation process, while removing most of the restrictions of the group A: the car should derive from a model family with a minimal production of 25.000 cars, of which a minimum of 2.500 should share the 2.0 16V engine, but in fact, only 20 kits had to be produced. Some significant modifications were allowed, such as the use of rear wings (at a limited size), front spoiler and enlarged wheel passes, while the size of cooling air inlets was also limited. And this is how the concept of World Rally Cars was born, in what we could name the second great aerodynamics era in the World Rally Championship, after group B.
C.Mcrae/N.Grist, Subaru Impreza S3 WRC, Rally Australia 1997, 1st – picture by Tym – ewrc.cz
New cars looked more aggressive, but the change was far away from becoming such a step ahead as group B was. The new category quickly obtained support from most of the teams, and Subaru and Ford redesigned their cars to meet the new category requirements, while Mitsubishi considered the advantages of keeping the car as a group A (and not to be restricted to WRC limitations listed above) and decided to postpone the transition to the new category for future years. For them, the construction of 2500 cars was not a problem, as such a number of cars of any version of the Evolution model had been sold very quickly, every time Mitsubishi launched a new car.
Leverage of car performances was one of the advantages everybody presumed before the start of the 1997 season, and to differentiate from the competence under such equality, aerodynamics played a significant role.
K.Eriksson/S.Parmander, Subaru Impreza S3 WRC, Rally of Indonesia 1997, 3rd. – picture by Tym – ewrc.cz
If one car is associated with the new concept, this is the Subaru Impreza WRC. Already present in the Championship since 1993 (Subaru Impreza 555), Prodrive searched the complicity of the Mclaren F1 designer Peter Stevens, in an attempt to design an icon that contributed to boost the image of the car as well as to attract the audience to the discipline, and they fully succeeded in both senses. Stevens worked hard on the aerodynamics and exterior design, while Engineering was lead, as usual, by Subaru Technical Director David Lapworth. They both developed a flowing design, based on the 2-door model, which included flared arches, a well-developed front and rear bumper and an impressive rear wing that gave the car a breakthrough image.
Once they completed the design (by March 96), they validated the design through tests in the MIRA wind tunnel, with the aid of parts clay modeling.
Images extracted from video Developing the 1997 Subaru Impreza World Rally Car, by Rallysights (full video).
Old Impreza design was considered to be so inefficient that the car still generated some lift, which in no way helped to turn faster. For this reason, the main goal of Stevens design was to convert the new car into a downforce-generating car, that is, to optimize the aerodynamic design of the car to a point that the contribution of the new parts to downforce was able to compensate, by far, the lift generated by the rest of the car. The front bumper was redesigned, with bigger air inlets and a more pronounced front splitter. Side skirts were also enlarged, and the rear bumper was modified to match the styling of the frontal. The main modification was the introduction of a big rear wing, with a top blade adjustable to different angles of attack (from 0 to 17º), and a wicker on the rear part of the hood.
C.Mcrae/N.Grist, Subaru Impreza S3 WRC, Tour de Corse 1997, 1st. – picture by Tym – ewrc.cz
The Impreza WRC was the first Subaru rally car entirely built in Prodrive facilities. The new car was finished just 3 weeks before its presentation to the press, which happened during the 1996 Catalunya Rally. After that, the first tests were developed in Catalan roads, in the preparation of the 1997 season, with Colin Mcrae, Piero Liatti and Kenneth Eriksson at the wheel.
The season start seemed to confirm the success of the new concept, as Subaru drivers ensured the victory in the first three rallies: Liatti in Montecarlo, Eriksson in Sweden and Mcrae in Kenya, driving what it was named the S3 version of the Impreza WRC.
P.Liatti/F.Pons, Subaru Impreza S3 WRC, Monte Carlo Rally 1997, 1st – picture by rallylife/Martin Holmes Rallying
But after that, engine problems affected the Japanese cars on several occasions, allowing Mitsubishi to replace Makinen at the front of the classification. Once solved, Colin Mcrae made an impressive final rush by winning in Corsica, Sanremo and Australia (even after losing his rear wing).
C.Mcrae/N.Grist, Subaru Impreza S3 WRC, Rally Australia 1997, 1st
Also, Eriksson won in New Zealand, adding to a total of 8 wins that allowed the team to ensure their third manufacturers’ title in a row, after those obtained in 1995 and 1996.
K.Eriksson/S.Parmander, Subaru Impreza S3 WRC, Rally of New Zealand 1997, 1st
Colin also won his home event, the RAC Rally, but the sixth position of Tommi Makinen gave the Finn the point he needed to get his second world Driver’s title.
C.Mcrae/N.Grist, Subaru Impreza S3 WRC, RAC Rally 1997, 1st – picture from ewrc.cz
For the 1998 season, a young Belgian engineer, who had joined Prodrive in 1991, Christian Loriaux, was named Chief Rally Engineer, and he significantly contributed to improvements such as electronically adjustable shock absorbers or an active rear differential, which were incorporated in the S4 version of the car.
P.Liatti/F.Pons, Subaru Impreza S4 WRC, Tour de Corse 1998, 3rd – picture by Tym – ewrc.cz
With the same drivers for 1998, the results were far from expected, as only Mcrae was able to win (in Portugal, Corsica and Acropolis Rallies), and the drivers and manufacturers titles escaped to Makinen and Mitsubishi.
C.Mcrae/N.Grist, Subaru Impreza S4 WRC, Rally Catalunya 1998, ret.
The season ended with a total renewal of the drivers, as Richard Burns, Juha Kankkunen and Bruno Thiry joined the team for the 99 season.
A new semi-auto and fully hydraulic transmission, a strengthened, stiffened and lightened bodyshell and revised engine internals with a new turbo were incorporated into the S5 version of the Impreza WRC, which first took part in the 1999 Rally of Monte Carlo. Juha Kankkunen drove this car to second place on the French roads.
J.Kankkunen/J.Repo, Subaru Impreza S5 WRC, Monte Carlo Rally 1999, 2nd – picture by Petr Fitz – ewrc.cz
But the car suffered from different problems, and results didn’t arrive until the second half of the season. Juha’s victories in Argentina and Finland Rallies and Richard Burns’ in Greece (Acropolis) put the team back into the fight for the titles.
R.Burns/R.Reid, Subaru Impreza S5 WRC, Acropolis Rally 1999, 1st – picture by Tym – ewrc.cz
Richard Burns completed an impressive end of the season, winning in Australia and Great Britain, but this proved to be insufficient to stop Tommi Makinen from obtaining his fourth crown, while Toyota ensured the Manufacturers title thanks to the regularity of Auriol and Sainz, even though they only obtained one single victory, in opposition to the five achieved by Subaru drivers.
R.Burns/R.Reid, Subaru Impreza S6 WRC, Rally Australia 1999, 1st – picture by LAT
For the 2000 season, a new version of the Impreza WRC was prepared, to replace the previous car, which was then the oldest WRC car. The S5 version was still aligned in the first rallies in 2000, contributing to a well-deserved 1-2 in Safari Rally and a third position in the Monte Carlo Rally for Kankkunen.
J.Kankkunen/J.Repo, Subaru Impreza S5 WRC, Safari Rally 2000, 2nd
Christian Loriaux led the team that developed the design of the Subaru Impreza WRC 2000 (version S6), in which Simon Carrier (later M-Sport Chief Design and currently at Toyota Gazoo Racing, where he has significantly contributed to the design of the Toyota Yaris WRC) also played a leading role. The new car had three active differentials and a lowered center of gravity. Different aerodynamic modifications were incorporated to improve car stability at high velocity. The front bumper was redesigned, with a modified lower air inlet (now square-shaped) and a bigger front splitter, to generate higher downforce by reducing the amount of air flowing below the car (see explanation here). Pictures below of the S6 and S3 cars for comparison.
R.Burns/R.Reid, Subaru Impreza S6 WRC, Catalunya Rally 2000, shakedown
C.Mcrae/N.Grist, Subaru Impreza S3 WRC, Sanremo Rally 1997, 1st – picture by fotosport
The rear wing was redesigned: the upper blade was shorter and thinner, while endplates were enlarged. Also, bonnet air vents were modified (enlarged).
R.Burns/R.Reid, Subaru Impreza S6 WRC, Catalunya Rally 2000, 2nd
C.Mcrae/N.Grist, Subaru Impreza S3 WRC, RAC Rally 1997, 1st – picture from ewrc.cz
The car outperformed since its first rally, and Burns drove it to victory in Portugal, Argentina and Great Britain.
R.Burns/R.Reid, Subaru Impreza S6 WRC, Rally of Portugal 2000, 1st
For the last rallies of the season, Subaru incorporated a young, brilliant driver, who years later became World Champion. His name: Petter Solberg.
P.Solberg/P.Mill, Subaru Impreza S6 WRC, RAC Rally 2000, ret. – picture by Petr Fitz- ewrc.cz
Marcus Gronholm, at the wheel of the Peugeot 206 WRC, obtained 4 wins and the 2000 Drivers title, while Peugeot won the Manufacturer’s title. Prodrive and Subaru were already working on a new car…. but this deserves another post.