Ayrton Senna moved from Toleman to Lotus for 1985 and won his first Formula One race in his second season, in car number 12.
It happened at Estoril. On Saturday 20 April 1985 he took pole with a 1:21.007, a new circuit record — Nelson Piquet's 1:21.703 from the year before had stood until then. Alain Prost lined up next to him. On Sunday the forecast rain came down as a deluge, and one by one the quick men went off: Keke Rosberg, Piquet, Prost, Niki Lauda. Senna led every lap and finished at least a lap clear of everyone except Michele Alboreto, who was second; Nigel Mansell took fifth, two laps down. He had his belts off and half his body out of the cockpit crossing the line.
The car ran the Renault EF15 — a 1,492cc V6 turbo, 137kg, a pair of Garrett AiResearch turbochargers, 810hp at 11,500rpm. It was built around fuel economy at high revs, because 1985 capped the race fuel at 220 litres and the cars had no computerised gauge; the drivers judged it themselves, and the engineers set boost per circuit to suit. Lotus was one of the few teams that could afford to qualify on a different engine, so they used an updated EF4 — the EF4B, which handled the boost better and could touch 1,000hp over a couple of laps — for qualifying, and saved the EF15 for the race.
It was a better car over one lap than over a race distance. Senna and his teammate Elio de Angelis took seven poles in 1985 and won three races between them, and a dozen pit stops for mechanical trouble across the sixteen rounds cost them the rest. Senna finished fourth in the championship with two wins, Estoril and Spa. Lotus still ended the year fourth in the constructors' on 71 points, more than 55 clear of the Renault works team — after which Renault withdrew its own team and became an engine supplier for 1986.