Fascinating video charting the early development of the Lancia Delta S4 Group B supercar.
Work began on the S4 project in April 1983 when it was code named the 038. Lancia officially launched the rally car in December 1984 and announced that the S4 would make its world championship debut on the 1985 1000 Lakes Rally.
Delays with the the car's development meant that the Lancia Delta S4 would actually make it's first WRC appearance on the RAC Rally in 1985.
The footage includes rare clips of the S4 during its initial testing phase at FIAT's La Mandria test track in November 1984 with Markku Alen and Giorgio Pianta (one of the project's key architects) at the wheel, the 1985 Mille Pistes Rally (where it ran in the prototype category with Alen), Henri Toivonen completing a series of demonstration runs around a race circuit for the purposes of the press in October '85 and BBC Top Gear Rally Report doing a feature on Markku Alen testing the car in Scotland ahead of the '85 RAC Rally.
The S4 engine, displacing 1759cc, is based on proven Abarth hardware and mounted longitudinally behind the front seats. In the 'production' cars its KKK turbocharger and Abarth Volumex supercharger boost output to a maximum of 250 bhp at 6750 rpm and 214 lb-ft of torque. That sounds a lot from less than 1.8 litres, but the similar-sized motor of the Lancia Martini rally cars was persuaded to yield a reliable 470 bhp at 8000 revs, plus more than 333 Ib-ft of torque.
The aim of using both a turbo unit and supercharging was to overcome the lazy low-speed response of the turbo. The supercharger looks after the provision of extra punch below about 3500 revs, and the turbocharger supplies an increasing amount of boost at higher rpm.
The competition S4 used exactly the same twin intercooler principles, but the transition from supercharging to turbocharging took place at higher engine speeds, between 5000 and 6000 revs. Developing the engine's mechanically driven supercharger and the exhaust-impelled turbo to the point where power and torque delivery were harmonious was a complex challenge. Fiat-Lancia-Abarth engineers eventually met it successfully, but as yet nobody else has repeated the experiment...
shalco.com
The spaceframe chassis Delta S4 (which probably had more in common with the Ferrari 250 LM of the mid- '60s than with any conventional rally car) had a very unique engine sound, with the Volumex compressor producing a distinct hissing noise similar to that of a pressure cooker.
video uploaded by Marvdogger
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Tags: algarve, development, engine, group b, henri toivonen, kkk turbo, lancia delta s4, Markku Alen, millie pistes, rac rally 1985, rare, specification, supercharged, testing, turbocharged, video, volumex compressor, wrc
