Video: ‘Full Throttle’ – Lancia’s prototype Group B Delta S4 in secret test

The Delta S4 is set to replace the two-wheel-drive 037 that had become outclassed in the fast and furious WRC formula against the total-traction might of Audi’s Sport Quattro and Peugeot’s mid-engined 205 T16 pocket rocket.

The Italian firm had realised that to beat its established Group B rivals, it would need to come up with something pretty spectacular. On paper, the mid-engined, turbocharged-and-supercharged S4 appears to tick all the boxes, but there would be plenty of hard graft to break in the Italian stallion.

On narrow and fast Italian roads, the team puts the unliveried S4 through its paces, with Markku Alén and veteran racer and team manager Giorgio Pianta on hand to perfect its power delivery and handling, while also dialling in that all-important robustness and reliability.

Their work, which is captured in this film during what otherwise appears to be a behind-closed-doors test, would pay huge dividends when the car made its WRC debut in the Lombard RAC Rally, the finale of the 1985 season. Flying Finns Henri Toivonen and the man in this film, Markku Alén, would guide the by-then Martini-liveried beasts to a dominant one-two in the British forests.