Lancia Delta S4: two-week world champion in 1986 with Mark Allen

The Lancia Rally 037, despite winning the 1983 Manufacturers’ World Championship, failed to match the four-wheel drive advantage of the competition cars. The answer of the Italian company was heard in the name Delta S4.

The Delta S4 was developed between 1985 and 1986 by Lancia in collaboration with Abarth. It was an absolute race car in every respect, with Lancia giving in to the transmission on all 4 wheels. The purpose of the Delta S4 was to continue the Rally 037 winning streak in the legendary Group B.

Under the hood the 1,759 cc engine. Combined mechanical supercharger and turbocharger to reduce turbo lag at low revs.

The official peak power price was 490 hp, although there were rumors that the total was over 500, which is by no means unlikely given that in 1985, when Lancia engineers tested the S4 engine in extreme operating conditions, 1,014 hp had been achieved with one pressure of 5 bar!

The Delta S4 brought the dual-boost process to the surface for the first time, with a large turbo Kühnle, Kopp & Kausch starting at 4,500 rpm. and a Volumex R18 mechanical supercharger that closed the power gap at lower revs.

The choice of displacement was anything but arbitrary, because according to the FIA ​​regulations and the factor 1.4 in the supercharged units, the S4 engine was below the limit of 2,500 cm³. which ensured the minimum allowable weight of 890 kg.

Like its competitors, the engine-centric Delta S4 had little in common with the corresponding production model, the Lancia Delta. As with the 037, the tubular space frame was sprung on all wheels with double wishbones, while the plastic body emphasized the aerodynamics and, of course, the quick repair of damage in the event of an exit.

The new all-wheel drive system that Lancia developed for the S4 in collaboration with British company Hewland featured a central differential with torque split between 60% and 75% to the rear wheels and offered a distinct advantage over the less advanced all-wheel drive systems of the competition.

The Delta S4 made an immediate impact when it won its first official RAC rally in 1985 at the hands of Henry Toivonen. The following year, Mark Allen and the S4 were 1986 World Champions for two weeks, a title eventually stripped after the Finnish driver’s victory at the San Remo Rally was annulled due to a technical fault.

In addition to the lost victory in the Italian race, the Delta S4 won 3 other victories in the same year, in Monte Carlo with Toivonen, in Rally Argentina with Nicki Biazion and in the Olympus Rally in the USA. with all.

In fact, Bizion’s victory in Argentina was his first win in the World Rally Championship! At the same time, Lancia won the European Rally Championship in 1986 with its impressive race.

The end of the Delta S4 came tragically when Henry Toivonen and his co-driver Sergio Cresto died after an exit on the 18th stage (Corte-Taverna) of the 1986 Corsica Rally, an accident that led to the immediate end of the frightening strong cars of group B

Lancia had already begun designing the futuristic Lancia ECV to replace the 1987 Delta S4, but the cancellation of the Group S, like Group B, led to the takeover of Delta production.

For the first time since Fulvia, Lancia was forced to rely on its racing presence in a production car rather than one designed specifically for rallies, a stipulation that would lead to the most successful race car in its history: the Lancia Delta HF race car.