1985 Lancia Delta S4

The Group B rally car pinnacle ranged from the class's inception in 1982 until its demise at the end of the 1986 season. Companies that invested heavily in the practically unlimited class included Audi, Citroen, Fiat, Ford, Lancia, Open, Peugeot, and Rover. This racing class entailed gladiator-like danger for drivers and co-drivers who pushed the limits of human potential through treacherous mountain passes, desert roads, and snow-covered woodlands. Teams used Space Age exotic materials, turbo-boosted horsepower, and technical ingenuity. As would be expected, the lack of safety precautions and high-power outputs led to a number of accidents, causing the sanctioning body to disestablish the class. The class did introduce a number of innovative automotive technologies, such as all-wheel drive, twin-turbocharging, and the use of space-age materials like Kevlar.

Audi's entry was the Quattro and was the first rally car to feature four-wheel drive, helping it win the championship in 1982 and 1984. Lancia responded with the Delta S4 in 1985. It utilized a tubular space frame, fully adjustable suspension, lightweight composite bodywork, a transmission driving all four wheels, and a diminutive, twin-charged – turbo and supercharged – 1.8-liter four-cylinder engine that could output over 500 bhp. Zero-to-sixty was accomplished in about two seconds.

Building upon the success of the Lancia Rally 037, engineers began work on a successor to the retiring rear-wheel-drive platform. The result of their efforts was the Delta S4. Their focus was on a lightweight, all-wheel-drive platform. The development team elected to conform to the requirements of the naturally-aspirated 2,500cc (forced induction limited 1,785cc) class to compete with its main opponent, the Peugeot 205 T16. In comparison to the 037, which had a larger displacement but heavier 3,000cc class, the Delta S4 was permitted to compete at a reduced minimum weight of 890kg. The Lancia Delta S4 won its first competitive outing at the 1985 RAC Rally and handed Markku Alen a second-place finish in the drivers' championship the next year.

The Delta S4 was the most powerful Group B Rally car that Lancia ever produced.

Homologation rules for approval in Group B competition required at least 200 'Stradale' - or street - versions of the model. The foundation of the Delta S4 chassis started with a CroMoly steel tubular space frame. Reinforced with aluminum alloy, the steel skeleton was then covered with epoxy and fiberglass body panels. With pick-up points for the suspension welded to the tube frame sections, maintaining and repairing the suspension proved a straightforward process. The latticed, tubular frame also permitted easy access to the engine, transmission, and all-wheel driveline for maintenance and repair.

Mounted within the tubular latticework of the rear section, engineers positioned the over-square (88.5mm bore x 71.5mm stroke) 1,759cc Lancia engine. Instead of seating iron or hard alloy cylinder liners, this engine featured aluminum cylinder bores with a hardened ceramic surface to cope with the demands of the combustion process. In full WRC race trim with calibration, the four-cylinder engine could have reached 480+ horsepower.

To compensate for the notorious turbo lag, Lancia incorporated a responsive, positive-displacement supercharger. The implementation of the first twin-charged forced-induction solution served in both the homologation vehicles and the full racecars. The engine powering the homologation vehicles employed a Weber-Marelli IAW Integrated Electronic Ignition and Fuel Injection system conservatively calibrated to generate 247bhp at 6,750rpm and 215 lb-ft torque at 4,500rpm.

A five-speed transmission was mated to the full-time all-wheel driveline of the twin-charged engine. This driveline included a new center differential that delivers a 30/70 torque split to the open front differential and the limited-slip rear differential, respectively.

The cabin of the Delta S4 featured a two-seat cockpit that was fitted with Alcantara upholstery, sound deadening, a suede steering wheel, power steering, a trip computer, and air conditioning.

by Daniel Vaughan | Oct 2017