In order for a vehicle to be able to take part in FIA approved races it has to be produced to a minimum number of units by its manufacturer, 5000 for the GroupN class, 2500 for the GroupA class and 200 for the now extinct GroupB. These units have to be similar, in aspect and mechanically, to the ones that will effectively take part in racing i.e. if the racing vehicle has a 4 wheel drive transmission so must also have the homologation base vehicle. Certain mechanical and electronic parts that are present in the racing vehicle must also be present in the homologation base unit. If modifications are required to the competition version then a new series of street going vehicles that include them will have to be produced. These cars were bred by racing for racing.
Logically manufacturers try to size the homologation base vehicle so that its racing counterpart will be as competitive and versatile as possible. For instance FIA rules impose that a GroupN class car cannot exceed the wheel size of the homologation base vehicle. Consequently the bigger the wheels and wheel arches mounted on the homologation base vehicle the more supple the choice of competition wheels will be. Another example is the size of the turbocharger that, if fitted to the homologation base, will have to maintain the same model and size on the competition vehicle. These rules, and many others discussed in further detail here for the GroupN class and here for the GroupA class, have pushed manufacturers to produce road going versions of vehicles destined to competition, the so called "Homologation Specials". Of course solutions applicable to racing vehicles are not the best suited to street going cars. Additionally it only matters that the street going version has the required equipment, dimensions and is produced in sufficient numbers and no particular care is usually taken to its finish or road manners.
October 1st 1974 saw the FIA homologation of the first ever homologation special.
It was the Lancia
Stratos HF (pictures here,
specification here), a purpose-built vehicle, homologated in Group 4
(500 identical cars produced over a period of 24 months were required to
obtain the homologation), and produced in 492
road-going copies between 1973 and 1975. The Lancia Stratos essentially
reversed the way car manufacturers used to approach racing. Instead of
choosing a large scale production model and adapting it to the
requirements of racing the Stratos was built as a race car that just
happened to have a road-going version.
The Lancia Stratos introduced many of the issues that were to affect FIA homologation car runs. It was extremely difficult to sell as a road-going car as it was introduced in the middle of an oil crisis and only obtained type approval for road use in Germany, Belgium, Switzerland, Holland and of course Italy. Hence many "Stradale" versions lay unsold well into 1978 at which point they were essentially given away. The car was very approximately finished and ill-mannered as it was a competition car under disguise and numerous manufacturing short comings plagued its road-going version. Most of these concerns were to afflict its homologation successors with very few exceptions. Finally an issue that was to later afflict GroupB car homologation runs (200 identical cars produced over a period of 12 months were required to obtain the homologation) also affected the Stratos. At the time of its FIA homologation (see above) a maximum of 141 cars had been built, far less than the required 500. This was to be the case in GroupB production runs as well were far less than the required number of cars were to be produced...
Cars such as the Subaru Legacy, the early BMW M3, the Audi Coupe Quattro or the Mitsubishi Galant VR4 and others are not true homologation specials as their production numbers were not dictated by FIA regulations and their design did not directly derive from a competition counterpart. These cars were used in competition only because the base car was already, or was thought to be, adequate for competition purposes.
Most of the homologation specials are recognizable by the number of air vents fitted on their bonnet, front bumper and wheel arches as well as their oversized spoilers and other aerodynamic attributes. These vents, usually blanked on the street versions, are not required for street use but are essential for competition use and have to be present on the homologation base vehicle.
The majority of homologation special cars have not been produced in numbers exceeding those required for their FIA homologation and are, thus, relatively rare and rapidly becoming collectable. Additionally they are often very exciting to drive as, most of them, are in fact detuned competition vehicles under disguise. For a manufacturer producing special series of cars that share very few common parts with other models is an expensive adventure that almost always leads to financial losses. Since the emergence of the WRC class cars in 1997, which do not require street going counterparts and thus represent a serious financial gain for manufacturers, production of homologation specials ceased.
Unfortunately there will most probably never be a second run of production cars displaying the character of the cars described above. Stringent emission control laws, noise level requirements and security features have clogged today's production cars with excessive weight, the number one enemy of any sports car, while their engines feel anemic and characterless when compared to those fitted in most of the 70s, 80s and 90s homologation specials. An era in the car production industry has come to an end.