The Lancia Delta S4 is a Group B rally car that competed in the World Rally Championship in 1985 and 1986, until Group B cars were banned from competition by the FIA. The car replaced the Lancia 037 Monte Carlo. The S4 took full advantage of the loose Group B regulations and was highly advanced. It featured a mid-mounted engine and all wheel drive for superior traction and handling. The car's 1759 cc four cylinder engine combined supercharging and turbocharging to reduce turbo lag at low RPM. Officially the car produced 550 horsepower (410 kW). Unofficial figures claimed the S4 could accelerate from 0 to 100 km/h on gravel in just 2.5 seconds.
For homologation purposes, Lancia built 200 road-going S4 Stradales. Like the rally car, these were mid-engined with 1.8-litre engines, producing 250 PS (180 kW; 250 hp) in road tune.
Source: Wikipedia (original)