[motorsportnerd]

I’ll start with the Group A cars. Group A was introduced as the main touring car category in Europe in 1982 to replace the older Group 1 rules. Under the rules, a manufacturer could race any 4-seater car of which a least 5,000 units had been built. A number of freedoms were allowed to modify the engine, exhaust and suspension. A car could be lowered, provided the wheels still fitted within the wheel arches. The body had to remain identical to the production car.
After building the basic 5,000 cars to allow for homologation, a manufacturer could build a further 500 “evolution” cars. This allowed the manufacturer to build cars with specific items that would make them more competitive on the race track, such as special suspension or engine components or spoilers and wings. The reasoning behind this was that it was cheaper to build 500 hotrods rather than have to put the special items on the 5,000+ basic cars.
Three class categories were introduced: Class 1 for over 2,500 cc cars, Class 2 for 1,601 to 2,500 cc cars and Class 3 for under 1600 cc cars. Turbo-charged and rotary power cars were required to add 1.4 to get their actual race capacity (ie a 2,000 cc turbo car was given a nominal 2,800 cc for racing). This penalty was increased to 1.7 after 1988.
The weight of the car depended on the engine size, and weights limits were changed several times during the life of the category. As a guide, minimum weights were as follows:
Over 5,000 cc cars - 1,400 kg.
4,501 cc to 4,999 cc - 1,325 kg (1,340 kg in 1988, 1,250 kg in Australia in 1990-92)
4,001 cc to 4,500 cc – 1,255 kg
3,501 to 4,000 cc - 1,125 kg
3,001 to 3,500 cc – 1,110 kg (1,100 kg after 1988, 1,150 kg in Australia in 1992)
2,501 to 3,000 cc – 1,035 kg (1,020 kg after 1988)
2,001 to 2,500 cc - 960kg (920kg after 1988)
1,601 to 2,000 cars - 880 kg
1,301 to 1,600 cc cars - 800 kgs.
The idea was that the cars of various classes and engine sizes would end up with similar power to weight ratios.
During the 1980s, Group A racing was adopted as the primary touring car category in Europe, Australia, New Zealand and Japan.