Têtu spent five years with
Charles Deutsch at Automobiles CD, joining in 1963 and staying until 1968.[6] While there he was involved with the Le Mans cars, initially the Panhard-engined
LM64, and later the Peugeot-powered SP66.[7][8]
Têtu moved to Ligier in 1969. His first major design was also Ligier's debut model, the
Ligier JS1, followed by the
Ligier JS3 sports racing barquette, and then the
Ligier JS2 sports coupé, both also Têtu designs.
He then joined Alfa Romeo's
Autodelta competition division. He had been brought in to consult on the aerodynamics of the
T33/2 Daytona coupé.[9][10] When he arrived in 1972, Têtu was put in charge of the eight-cylinder Tipo 33s, which were near the end of their development life.[1] He also drew the shape of the
Alfa Tipo 33 TT 12 that won the
1975 World Championship for makes.[11][12]
In 1976, Têtu was contacted by
Gérard Larrousse, then with Renault, about the possibility of him joining the company for a special project.[1][13] Têtu returned to France and began working for
Renault Sport in Dieppe. He became one of the lead engineers on Renault's Projet 822, which was released as the
Renault 5 Turbo.[14][15][16][17] He was asked to drive the prototype on its first outing.[13]
Têtu's other projects at this time included preparing
Alpine A310s for Group 4 competition.[13][18][19] He also developed the Renault 5 Alpine Group 2 rally car, which finished second and third at the 1978
Monte Carlo Rally.[20][3]
In 1978 Têtu moved to the
Renault Formula 1 team full time. He designed Renault's first
ground effect F1 car, the RE10 (also called the
RS10).[24][25] Driven by
Jean-Pierre Jabouille and
René Arnoux, the RS10 became the first F1 single-seater with a
turbocharged engine to win a Grand Prix race. Têtu went on to design the RE20, RE30, RE40, and RE50, finally leaving Renault in 1984.
In 1985, Têtu went to
Équipe Ligier, for whom he designed the
JS27, and
JS29. After the failure of his innovative
Ligier JS31 in 1988, Têtu was fired by Ligier. He then went to the independent Larrousse F1 team, where he designed cars until the end of 1994.[26][27] He later returned to Ligier Automobiles for a stint that had him designing "voitures sans-permis", microcars that can be driven in France without an operator's license.
After leaving Larrousse, Têtu also served as technical adviser for race car builder
Mygale.[28] Their MT01
Formula Ford chassis carried Têtu's initials.[29]