Lancia Delta S4

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Lancia Delta S4

4 cyl. Turbo / Supercharger
1759 cc
250 bhp
5 spd. man
Top Speed:
140 mph
Number Built:
5 star
Lancia Delta S4
Lancia Delta S4
Reviewed by Unique Cars and Parts
Our Rating: 5


Being one of the most high-tech cars ever built, the Lancia Delta S4 had a legendary and dramatic fate. It had actually no relationship with the production Delta series (the most noteable difference being the mid-engined design and tubular space frame chassis).

Designed for racing from day one, the Lancia clearly had the Peugeot 205T16 and Audi Quattro Sport in Group B world rally championship in its sights. Lancia's Monte Carlo rally car was, by 1985, seriously outgunned in performance by the Pug and Audi, giving up some 60 bhp to its rivals.

Compounding the performance issues was the fact that the Lancia was a 2WD competing against 4WD rivals. While the Delta S4 was styled and named to promote the mass-production Delta, it was in actually a clean sheet design.

Adopting the more popular mid-engined layout, the S4 engine was longitudinally mounted behind the front seats, directly driving the viscous-coupling LSD which transfered 30% torque to front wheels and 70% to the rear.

At each of the corners of the steel tubular space frame chassis, the suspension used double wishbones with twin absorbers. The body was a composite glass-fibre/epoxy resin. While its 4WD system was not as advanced as the Peugeot 205T16's (which had variable torque split between front and rear axles), its engine far more advanced, employing both a turbocharger and supercharger simultaneously.

A turbocharger is generally regarded as the most efficient means of forced induction, but it requires higher revs (hence a lot of exhaust gas) to operate. The result is poor low-speed power and the presense of turbo lag.

A supercharger performs strongly and instantly right from idle, but it is rahter inefficient at high rpm. For a rally car, a flat torque curve over a wide range of rpm is always crucial - and that is why Lancia spent a lot money with Abarth to develop a system combining both turbocharger and supercharger.

The S4 employed twin intercoolers, one for the turbo and one for the supercharger. The supercharger worked at low speed, and when the turbo cut in, a bypass valve relieved the pressure from the supercharger so that energy efficiency was lifted. The result of the combined turbocharger and supercharger meant that the 1.8-litre engine produced a mind blowing 250 bhp and a healthy 214 lbft of torque, while the rally car upped that to 470bhp and 333 lbft.

Like other Group B cars, only 200 units of road version were made to fulfill the minimum requirement for homologation. In WRC, the Delta S4 experienced a dramatic fate. It won its debut race, then continued to dominate the following races and was leading both the driver and manufacturer championship standings. Such excellent results amazed everyone, since it was a completely new car.

Sadly, during the 1986 Tour de Corse (Corsica Rally), driver Henri Toivonen and navigator Sergio Cresto (who were leading the race) crashed in their S4 and both were killed. The team lost its momentum and eventually handed the title to Peugeot. This accident led to the rethink of Group B cars. Races went on but finally FIA annouced the termination of Group B, because it was too powerful and dangerous. Therefore, Delta S4 became the most outstanding rally car in history not to win a world title.

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