Throughout the 1980's, motorsport was known through three letters: A, B, and C. Meant to replace the numbered categories of the 1970's, it brought a simpler classification method to different branches of motorsport. Over time, Group A came to be associated with touring cars, Group C was known for its Le Mans prototypes, and Group B was utilized in rallying.
With regulation dictating a homologation run of only 200 road cars, an "evolution" clause that allowed improvements to only be applied to 20 more cars, and almost no restriction on weight and power, Group B gave birth to some of the most advanced rally cars ever built, and what some argue to be one of the best eras of rallying.
The Group B regulations gave way to some of the most exotic machinery to ever take on the rally stages. (Photo: Autoglym)
Meanwhile, Lancia was caught off guard by the rapid development of the opposition. They won the constructors championship in the early days of Group B with the RWD 037 back in 1983, but with the advantage of 4WD starting to become clear with the Audi Quattro, more and more manufacturers decided to take advantage of the layout. Cars like the Peugeot 205 T16 brought the fight to the Quattro with a lighter spaceframe chassis, which made it dominate throughout the 1985 season. If Lancia were to take the championship once more, it had to take full advantage of the lax regulations. The product of which was the Delta S4.
Based on the Delta HF road car, the S4 would incorporate an improved version of the 037's fully tubular space frame construction. The bodywork was built out of carbon fibre composite for decreased weight and added rigidity. This use of exotic materials made the car weigh in at 1050 kg. But perhaps the most interesting aspect of this rally car is the mid-mounted engine that propels it.
The front and rear sections of the car were built in one "clamshell" piece for ease of access during repairs. (Photo: Motor1.com)
The 1.7 liter inline 4 was both turbocharged and supercharged, taking the advantages of the two methods of forced induction. The supercharger provided the boost at lower RPM's, while the turbocharger kicks in at the top end of the rev range. This ensured power was always available at all times. Overall, the twincharged engine produced more than 550 horsepower at 8400 RPM and 362 lb-ft of torque by 1986, although there were rumors that the car exceeded 800 horsepower. Nevertheless, the power made its way through a five speed manual gearbox and powered all four wheels of the car. With all this in play, the car managed to sprint to 100 kph in 2.4 seconds on tarmac, making it one of the fastest cars of the time.
The car made an astonishing debut at the 1985 RAC Rally where it claimed a 1-2 finish with Markku Alen and Henri Toivonen at the helm. Toivonen then claimed another victory at the 1986 Rallye de Monte Carlo, cementing the car's status as a challenger to Peugeot's control of the championship. In the snowy banks of Sweden, Alen was able to finish 2nd, while Toivonen dealt with a retirement caused by an engine failure.
A crash at Rally Portugal showed the danger of not only the Group B cars themselves, but also the crowds that swarmed the sides of rally stages while cars ran past with mere inches dividing the cars and the spectators. Joaquim Santos, while racing his Ford RS200, lost control and drove directly into the spectators, taking the lives of three people and injuring 30 more. All factory drivers decided to withdraw from the event.
The accident already had some people concerned about the safety of these cars, which were already becoming too fast even for their drivers to keep up with. On May 2, 1986, at the Tour De Corse Rally, Toivonen and his co-driver, Sergio Cresto, drove off a mountainside. The car rolled down the embankment, was caught by a few trees, and caught fire. Although the specifics of the crash were never exactly known, its results were clear. It took the lives of both Cresto and Toivonen, and hours after the crash, Group B and it's supposed successor, Group S, had their developments stopped and eventually, its cancellation.
The Lancia Delta S4 is known as one of the most advanced rally cars to ever come out of Group B's madness. Made as Lancia's attempt to claw its way back to the top, their persistence immediately paid off as their S4 became a tough contender for the championship. The car brought out the full potential of Group B's advancements, but it was also responsible for bringing its apparent danger into light after a crash that contributed to Group B's abrupt end. The Lancia Delta S4 came to be as the fatal finale to the absolute madness that was Group B Rally.