The Ferrari 126C was designed to replace the highly successful but obsolete 312T series in use since 1975. The basic chassis was almost identical to the previous car but the smaller V6 turbo engine suited the ground effect aerodynamics now needed to be competitive, and was a better package overall. During engine development Ferrari experimented with a Comprex pressure wave supercharger, however due to packaging issue the engine was finally fitted with twin KKK turbochargers and produced around 600bhp in qualifying trim, detuned to 550bhp for the races proper. The car proved to be very fast but Gilles Villeneuve found the handling to be atrocious. The engine had massive turbo lag, followed by a ferocious power curve; this upset the balance of the chassis. Coupled to the chassis' hard suspension, the car tended to slide into corners before the ground effect pulled the car back on to the track.
1983 saw the mandatory introduction of the flat bottom cars, reducing ground effect, and the 126C3 was designed with this in mind. Poslethwaite designed an over-sized but effective rear wing which clawed back around 50% of the lost downforce, whilst further compensation came from the engineers who boosted the power of the engine even further, to around 700bhp. Patrick Tambay and René Arnoux scored four wins between them and were both in contention for the world championship throughout 1983 but late unreliability cost them both. However, Ferrari took the constructors' title for the second year in a row.