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 by the FIA.

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.

The all-wheel drive system, developed in cooperation with English company Hewland, featured a centre differential which allowed for 60-75% of the torque to go to the rear wheels.

The Abarth Volumex R18 supercharger was the twin of the turbo, providing low to mid range boost and improving engine response and driveability of the S4.

[6] Lancia designed their twincharger system so the supercharger provides instantaneous boost in the lower range, switching to the turbocharger for more efficient operation at higher engine speeds.

The Stradale's chassis was a space frame, similar to its rally counterpart, 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, the 1.8-litre four-cylinder engine was longitudinally mid-mounted, equipped with Weber-Marelli IAW integrated electronic ignition and fuel injection, a supercharger, a turbocharger and two intercoolers.

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.

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.