The McLaren MP4/2 was a Formula One car designed by John Barnard of McLaren for the 1984, 1985 and 1986 season and powered by a 1.5 Litre, 90° V6 TAG-Porsche turbo engine that produced 650 bhp (485 kW; 659 PS) in race set-up and up to 800 bhp (597 kW; 811 PS) in qualifying set-up i.e. with maximum turbo pressure.
The MP4/2 was one of the few F1 cars to use carbon brakes at the time, giving it another major advantage over most of its rivals on all bar the street circuits or when conditions were hot and dry; notably, the carbon brakes were not as good as the steel brakes at tracks like the Detroit and Dallas street circuits due to the steel brakes lasting longer in the heat. That, combined to superior fuel consumption of the allowed 220 litres and the driving skill of Lauda and Prost saw the MP4/2 score 12 wins in 1984, at the time the highest number of wins in a season by a single team. Lauda beat Prost to the championship by just half a point in the final race, even though Prost had 7 wins to Lauda's 5 (at the final round in Portugal, Prost needed to win and have Lauda finish 3rd or worse to take the title. Lauda finished second). This remains the closest finish to a championship in Formula One history.
For 1985, the MP4/2 was updated with cleaner aerodynamics and redesigned wings (to comply with new regulations which banned the "winglets" on the rear wings of the cars which had been in use since 1983) and was dubbed the "MP4/2B", while Porsche refined the TAG engine with improved power (850 bhp (634 kW; 862 PS) in race and 960 bhp (716 kW; 973 PS) in qualifying) and fuel consumption. The suspension had to be redesigned after McLaren were forced to switch from Michelin to Goodyear tyres when the French company pulled out of Formula One. However, the competition had more or less caught up. The MP4/2B was as good a car as its predecessor, and retained its superiority on high-speed circuits made up of long, fast corners that were not flat out such as Jacarepagua, Silverstone, the Österreichring, Kyalami, and Brands Hatch.
Alain Prost's victorious MP4/2c Tag Porsche
The MP4/2 was virtually unchanged in 1986, with the exclusion of some tweaking in aerodynamics which saw it dubbed the "MP4/2C", while Prost was joined by Finn Keke Rosberg, the 1982 World Champion when driving for Williams. Rosberg was expected to not only be faster than Prost, but also to push for Prost's championship. By 1986 the Williams FW11 had overtaken McLaren as the best car; notably, the MP4/2's mileage was not as good as it was in 1984, with the fuel tank reduced in size from 220 litres to 195 litres (the TAG's fuel mileage was hurt by the increased speeds). Nelson Piquet had left Brabham to join Nigel Mansell at Williams and the two fought a fierce internal battle, while Prost cleverly built up his points total and snatched 4 wins from under the Williams teammates' noses.
Prost's second world championship was won more by stealth than speed as by now it was clear the TAG Porsche engine was past its best. The TAG-Porsche V6 engine was producing some 850 bhp (634 kW; 862 PS) in race trim by 1986 compared to 900 bhp (671 kW; 912 PS) of the Honda, Renault and BMW engines. In qualifying BMW was rated the most powerful at 1,400 bhp (1,044 kW; 1,419 PS), Renault and Honda engines had approximately 1,200 bhp (895 kW; 1,217 PS). Ferrari allegedly had the same amount of power as the Honda's, but their Ferrari F1/86 was uncompetitive on all but the smoothest of tracks and was generally not a threat.
Prost won his second championship in dramatic circumstances at the season ending Australian Grand Prix. The MP4/2 won 22 Grands Prix (Prost, 16; Lauda, 6), took 7 pole positions (Prost, 6; Rosberg, 1), and scored 327.5 points throughout its three-year career. It contributed to 2 Constructors' and 3 Drivers' championships, and remains the most successful chassis in F1 history.
Porsche built TTE P01 engine