Category Group B Predecessor Lancia 037 | Constructor Lancia | |
 | ||
Successor Lancia ECV
Lancia Delta HF 4WD Chassis Steel tubular space frame Suspension (front) A-arms, coaxial coil springs and dampers | ||
The Lancia Delta S4 is a Group B rally car from the Italian car company Lancia. The Delta S4 competed in the World Rally Championship in 1985 and 1986, until Group B class was disbanded and the cars were eventually banned from competition completely by European sanctioning body FIA. The car replaced, and was an evolution of, the Lancia 037. The S4 took full advantage of the Group B regulations, and featured a midship-mounted engine and all-wheel drive for superior traction on loose surfaces.
Contents
Specifications
The car's 1,759.3 cc four-cylinder engine combined supercharging and turbocharging to reduce turbo lag at low engine speeds. The car produced a maximum output of 480 horsepower (350 kW), but some sources even claim that the Delta S4 was capable of producing 500 horsepower (417 kW). In 1985, Lancia engineers tested an S4 engine under extreme conditions, reaching 5 bars boost, developing around 1000 horsepower. An engine capacity multiple of 1.4 was applied to forced induction engines by the FIA and the choice of 1,759 cc put the S4 in the under 2,500 cc class, which allowed for a minimum weight of 890 kg (1,962 lb). The combined super/turbocharger system (often referred to as twincharging) was a development of the 037 engine that produced 350 hp (261 kW) with a supercharger only.
Like Peugeot's earlier 205 T16, the mid-engine Lancia Delta S4 was a Delta in name and body styling only (for marketing purposes), and shared virtually nothing in terms of construction with the production front-engine Delta. The chassis was a tubular space frame construction much like the 037. It featured long travel double wishbone suspension front and rear, with a single large coil over at the front and separate spring and twin shock absorber at the rear. The bodywork was made of a carbon fibre composite with front and rear bodywork fully detachable for fast replacement due to accident damage, allowing ease of access during on-event servicing. The bodywork featured several aerodynamic aids including bonnet opening behind the front-mounted water radiator with Gurney flap, front splitter and winglets moulded into the front bumper panel, flexible front skirt, and rear deck lid wing that featured both a full aerofoil wind section twinned with a deflection spoiler. The door construction style was brought from the 037 with a hollow shell all-Kevlar construction that had no inner door skin, no door handle or window winder. The door was opened with a small loop and the windows were fixed perspex with small sliding panels to allow some ventilation and passing of time cards and suchlike.
The all-wheel drive system, developed in cooperation with English Hewland, featured a centre differential which allowed for between 60 and 75% of the torque to go to the rear wheels.
The Group S Lancia ECV was to replace the Delta S4 in the 1987 season but Group S was scrapped along with Group B and Lancia used the production-derived Delta in 1987.
Twincharging
The method of turbocharging and supercharging an engine is referred to as twincharging. The Delta S4 was the first such example of this technology. Contemporary turbochargers were inefficient, as they did not produce boost at low RPMs. This phenomenon, known as turbo lag, negatively affects driveability, an important aspect of a rally car. Superchargers do not suffer from lag as they are powered directly from the engine's crankshaft, rather than by the exhaust gases. However, because of this direct mechanical connection, the supercharger presents a significant parasitic load to the engine at higher RPMs. Lancia designed their twincharger system so the supercharger provides instantaneous boost in the lower RPM range, switching to the turbocharger for more efficient higher RPM engine operation.
Delta S4 "Stradale"
Between October 1985 and 1986 Lancia built 200 examples of a road-going version of the Delta S4, officially named Lancia Delta S4 but widely known as "Stradale", for the purpose of homologation in Group B. In Italy the car was priced at about 100 million Lire: five times the price of the most expensive Delta of the time, the HF Turbo.
The Stradale's chassis was a space frame, similarly to the racing cars, built out of CrMo steel tubes and aluminium alloy for the crash structures; it was covered by epoxy and fiberglass body panels. Like the rally car these cars mounted in a midships position a 1.8-litre engine, equipped with Weber-Marelli IAW integrated electronic ignition and fuel injection, a supercharger, a turbocharger and two intercoolers. In road tune the 1.8 produced 250 PS (184 kW; 247 hp) at 6750 rpm and 291 N·m (215 lb·ft) at 4500 rpm. The "Stradale" kept a three differential four-wheel-drive system; the centre differential sent 30% of the engine torque to the front open differential, and 70% to the rear limited slip one.
Lancia claimed the car could reach top speed of 225 km/h (140 mph) and accelerate from standstill to 100 km/h (62 mph) in six seconds. In contrast to its bare bones racing sisters, the S4 Stradale featured an Alcantara-upholstered interior, sound deadening, a suede steering wheel, and was equipped with power steering, trip computer and air conditioning.
Motorsport
In competition the car won its first event, the 1985 RAC Rally in the hands of Henri Toivonen and carried Markku Alén to second in the drivers' championship the following year. For two weeks after the end of the 1986 season Alen was champion until the FIA annulled the results of the Sanremo Rally due to irregular technical scrutineering. Alén had won that event and the loss of points handed the title to Peugeot's Juha Kankkunen. All told, in 1986 there were 3 wins for the Delta S4 (San Remo not included). The Monte Carlo Rally by Toivonen, Rally Argentina by Massimo Biasion and the Olympus Rally by Alén. The car also won the 1986 European Rally Championship with Italian driver Fabrizio Tabaton, whose car was run by Italian team HF GRIFONE in ESSO livery. The factory supported Jolly Club team also ran cars in TOTIP livery, one of which was for Dario Cerrato. The car competed at every rally that year except for the extremely demanding and gruelling Safari Rally in Kenya, where Lancia decided that the Delta S4 was not developed enough for that event, so they decided to use the older 037 for Alen, Biasion and 3 local drivers who were regulars in the event.
The car's legacy was tainted by the fatal crash of Toivonen and co-driver Sergio Cresto on the 1986 Tour de Corse, where the Finnish driver inexplicably missed a tight left-hand hairpin bend and plunged into a ravine, incinerating the car and the two drivers.