The Group B rallying era produced some astonishing machines, with many becoming household names. Lancia’s Delta S4 was arguably the most potent of its breed

The Lancia 037 was one of the greatest rally fighters of the Group B era. It was, and still is, the only rear-wheel-drive car to win the world championship against the more advanced all-wheel-drive competition. However, that glorious 1983 victory wasn’t enough to stop the new breed of mid-engine all-wheel-drive rally cars, and Lancia knew it. The solution was one of the greatest Group B cars of all time; the Delta S4.

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Lancia Delta S4: The ultimate Group B machine

There was still merit to the 037’s design, and so the Abarth engineers responsible for Lancia’s rally cars designed a similar tubular space frame to keep weight to a minimum — under 950kg was the goal.

Group B’s popularity made rallying a bigger global focal point than Formula 1 at the time – a perfect platform to market a new product. For marketing reasons it was decided that the new Lancia rally car should resemble the Delta hatchback – however, the racer shared very little with the road car.

To be called the S4 (S for supercharged and 4 for four-wheel drive), the new model started as a rear-wheel-drive prototype before shifting to powering all four wheels. It was quickly discovered that the engine produced too much power for the back tyres to handle. Said motor was actually derived from F1, and was supercharged as well as turbocharged. This method meant that there was a good spread of power throughout the rev range and a distinct lack of turbo lag.

Lancia Delta S4: The ultimate Group B machine

The S4’s bodywork wasn’t pretty, but it was functional. The lightweight carbon-Kevlar panels formed structures that dramatically increased downforce and aided cooling. Wind-tunnel testing resulted in the car sprouting a sizeable roof-mounted spoiler, large intakes and a Gurney flap on the bonnet.

Its debut event was the 1985 RAC Rally in the UK, where a pair of S4s finished a dominant first and second. In the hands of Henri Toivonen it also claimed victory in the following 1986 Monte Carlo Rally.

However, the S4s mastery came at a price. The car was fragile, and often required chassis repairs during events and a full rebuild upon its return to Italy. Lancia even decided to use an old 037 on the Safari Rally for fear of destroying the Deltas altogether. Another, more terrifying issue was that the accelerator pedal could become trapped in cracks that developed along the composite floor!

The Lancia Delta S4 was tinkered with throughout its career, with power starting at around 450bhp but often exceeding 550bhp. An upgraded engine for the Olympus Rally in 1986 was rumoured to produce close to 750bhp. It has been said, but never officially confirmed, that Toivonen tested an 800bhp version of the S4 at the Estoril track, and came within seconds of F1 qualifying times.

Lancia Delta S4: The ultimate Group B machine

Lancia was a safe bet to win both the driver’s and constructor’s championships in 1986. However, a tragic crash at the Portuguese Tour de Corse that year resulted in the death of star driver Toivonen and his co-driver Sergio Cresto. Nobody witnessed the incident, but it’s thought that the car hit a stone wall, tumbled down an embankment and came to rest in some trees.

The car’s aluminium fuel tank was pierced in the crash, creating an intense inferno. Back in the Group B era there weren’t any air ambulances or fire marshals along the route. By the time help arrived, it was all over.

The 1986 Portuguese Rally deaths were the latest in a spate of high-profile incidents in Group B rallying. After a car then crashed into a crowd of spectators, the cold, hard truth that Group B had become too fast and too dangerous was realised. The drivers went on strike, and Group B was disbanded shortly after.

It’s fair to say that the Lancia Delta S4 was the ultimate Group B rally car. The fastest, the most advanced – simply the best.