Lancia Delta S4
Group B twincharged mid-engine all-wheel-drive rally car from Lancia.
The Lancia Delta S4, known internally by its Abarth project code SE038, was a Group B rally car built by Lancia. It competed in the World Rally Championship during the 1985 and 1986 seasons, after which the FIA disbanded Group B and banned the cars. The S4 succeeded the 037 and was an evolution of that model. It exploited the Group B regulations to the fullest, with a mid-mounted engine and all-wheel drive that gave it exceptional grip on loose surfaces. Only 28 complete chassis were ever made.
The car’s 1759 cc inline-four engine used both a supercharger and a turbocharger—a system called twincharging—to eliminate lag at low revs. This setup was a development of the 037’s engine, which had produced 325 hp with only a supercharger. The FIA applied a 1.4 multiplier to forced-induction engine capacity, and the 1759 cc choice placed the S4 in the under-2,500 cc class, allowing a minimum weight of 890 kg. The engine delivered a maximum of 490 PS, though some sources claim it could reach 500 PS.
Like the Peugeot 205 T16, the S4 was a silhouette racer built for marketing, sharing almost nothing structurally with the front-engine production Delta. Its chassis was a tubular space frame, similar to the 037. Suspension was double wishbone at both ends, with long travel, a single large coil-over at the front, and separate springs with twin shock absorbers at the rear. The bodywork was made of carbon-fibre composite, with fully detachable front and rear panels for quick replacement after damage and easy access during servicing. Aerodynamic features included a bonnet opening behind the front radiator with a Gurney flap, a front splitter and winglets moulded into the bumper, a flexible front skirt, and a rear deck lid wing combining a full aerofoil section with a deflection spoiler. The doors were hollow Kevlar shells with no inner skin, handles, or window winders; they opened via a small loop, and the fixed perspex windows had small sliding panels for ventilation and passing time cards.
The all-wheel-drive system, developed with Hewland, used a centre differential that sent 60–75% of torque to the rear wheels. The five-speed transmission was also from Hewland. The Group S Lancia ECV was intended to replace the S4 for 1987, but Group S was scrapped alongside Group B, so Lancia used a production-based Delta for the 1987 season.
Twincharging was the S4’s key innovation.
Quick Facts
- Category
- Group B
- Predecessor
- Lancia 037
- Successor
- Lancia ECV / Lancia Delta HF 4WD
- Chassis
- Steel tubular space frame
- Front Suspension
- A-arms, coaxial coil springs and dampers
- Rear Suspension
- A-arms, coil springs, double dampers
- Length
- 3990 mm
- Height
- 1344 mm
- Wheelbase
- 2440 mm
- Weight
- 890-1050 kg
- Capacity
- 1759 cc Lancia 233 ATR 18S
- Configuration
- DOHC 16v I4
Facts from the source article.
Lore & Background
The Delta S4 was developed from the 037 and used a tubular space frame chassis, much like its predecessor. The bodywork was made of carbon fibre composite, with fully detachable front and rear panels for rapid replacement after accident damage. The door construction was a hollow Kevlar shell with no inner skin, fixed perspex windows, and small sliding panels for ventilation and time card passing. The all-wheel-drive system, developed with Hewland, featured a centre differential sending 60-75% of torque to the rear wheels. The car's twincharging system used a Kühnle, Kopp & Kausch 27 turbocharger with a boost threshold of 4500 rpm and an Abarth Volumex R18 supercharger for low- to mid-range boost, switching to the turbo at higher engine speeds. The engine produced 490 PS, with some sources claiming 500 PS. A road-going homologation version, the Delta S4 Stradale, was built in fewer than 100 units, featuring a CrMo steel space frame, epoxy and fiberglass body panels, and a 250 PS engine. The Stradale had a fully synchronized 5-speed CIMA transmission and a three-differential four-wheel-drive system sending 30% torque front and 70% rear.
Reader's Guide
The Delta S4 won its first event, the 1985 RAC Rally, driven by Henri Toivonen. In 1986, it scored three WRC wins: the Monte Carlo Rally (Toivonen), Rally Argentina (Massimo Biasion), and the Olympus Rally (Markku Alén). Alén finished second in the drivers' championship that year, and for two weeks after the season ended he was champion until the FIA annulled the Sanremo Rally results due to irregular technical scrutineering, handing the title to Peugeot's Juha Kankkunen. The car also won the 1986 European Rally Championship with Fabrizio Tabaton. 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 car left the road, plunged into a ravine, and burst into flames. The accident led directly to the abolition of Group B. The planned replacement, the Group S Lancia ECV, was scrapped along with Group B, and Lancia used the production-derived Delta for the 1987 season.
Did You Know?
- The Delta S4 was the first car to use twincharging, combining a supercharger and turbocharger.
- Only 28 complete rally chassis were built, and fewer than 100 Stradale road versions.
- The car's engine capacity of 1759 cc, multiplied by 1.4 for forced induction, placed it in the under 2500 cc class.
- The fatal crash of Henri Toivonen and Sergio Cresto on the 1986 Tour de Corse led directly to the abolition of Group B.
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