The Fiat 131, introduced at the 1974 Turin Motor Show, was a mid-size family car with conventional front-engine, rear-wheel-drive layout, steel monocoque bodywork, and fully independent front suspension via MacPherson struts. The base car used overhead-valve engines derived from the 124, with a solid live rear axle. This platform, while unremarkable in road trim, proved adaptable for high-level competition.
In 1976, Fiat produced 400 examples of the 131 Abarth Rally for Group 4 homologation purposes, a strict minimum required to certify the car as a legitimate production-derived competition vehicle. These cars were built through a collaboration between Fiat, Bertone, and Abarth, with the team under strict instructions to stay as close as possible to the base model in both parts and appearance.
Bertone took part-completed two-door standard bodyshells from the Mirafiori production line and fitted plastic mudguards front and rear, a plastic bonnet and bootlid, and modified the metal structure to accept rear independent suspension in place of the standard live axle. The bodies were fully painted and trimmed at Bertone before being delivered to Fiat's specialist Rivalta plant, where Abarth installed the competition mechanicals.
The homologation road car used a double overhead camshaft, four-valves-per-cylinder derivative of the standard twin-cam inline-four engine, equipped with a double downdraught Weber 34 ADF carburetor. Output was 140 PS at 6,400 rpm with 172 N·m of torque at 3,600 rpm. Road cars retained the standard gearbox — rally regulations required the same type of synchromesh as on the competition versions — and used stock front brake discs, though the revised Bertone front end improved cooling airflow.
In full competition specification, the engine produced up to 240 PS by 1980, eventually fitted with Kugelfischer mechanical fuel injection and dry-sump lubrication. The rear wheels used disc brakes in place of the standard drums.
The 131 Abarth's debut season in 1976 announced Fiat's serious intentions in international rallying. The car quickly established itself at the front of the Group 4 field, taking the Manufacturers' Championship in 1977 in its first full season.
In 1978, Markku Alen won the FIA Cup for Drivers with the 131 Abarth. That same year the car retained the Manufacturers' title. After a season in which competition intensified, Walter Röhrl drove the 131 Abarth to the 1980 World Rally Championship Drivers' title, giving Fiat its third and final Manufacturers' crown that year.
Other notable drivers who competed in the 131 Abarth included Sandro Munari, Timo Salonen, Attilio Bettega, and Michèle Mouton. The car ran under the Olio Fiat blue and yellow livery from 1975 to 1977, then switched to the distinctive red, white, and green Alitalia colors from 1978 through the 1979 season.
The 131 Abarth won 20 WRC events in total across its career, competing successfully in a wide range of conditions from the Monte Carlo Rally's mountain stages to African gravel.
The Fiat 131 Abarth's three Manufacturers' Championships represent the high-water mark of rear-wheel-drive Italian rally engineering before the Group B era. The car's development by Abarth — a marque synonymous with Italian motorsport tuning — produced a machine capable of beating the best in the world on both tarmac and gravel. Walter Röhrl's championship win in particular demonstrated that the car could deliver results even as competition grew sharper. The 131 Abarth bridged the gap between the pioneering Lancia Stratos and the turbocharged era that followed, and its success helped establish Fiat's credibility as a major force in world motorsport during the period.