The MP4/3’s design represented a significant departure from its predecessor, the MP4/2. The car’s aerodynamics were completely revised, resulting in a much lower-slung profile designed to maximize fuel capacity within the 195-litre limit, a reduction from the 220-litre limit used in 1984 and 1985. The exterior shape was all-new and sleeker, though it retained a similar nose section, which was also redesigned and reduced in size by approximately 10%. The design process was led by Steve Nichols, in collaboration with Neil Oatley, Gordon Kimball, Tim Wright and Bob Bell.
The MP4/3’s lowline design drew comparisons to the Brabham BT55 used by the Brabham team in 1986. Following Gordon Murray’s move to McLaren as Technical Director, it was widely believed he had significantly influenced the MP4/3’s design. However, McLaren team manager Jo Ramírez downplayed Murray’s involvement, stating the BT55’s design had no bearing on the car and that Murray focused primarily on quality control. Murray later claimed the MP4/3, and its successor the MP4/4, were based on his original Brabham BT55 drawings, which he had brought with him to McLaren. This claim was disputed by Steve Nichols and other McLaren engineers.
The MP4/3 continued to utilize the 1.5-litre TAG TTE PO1 twin-turbo V6 engine, but with adjustments to compression and engine balancing to accommodate the reduced fuel limit and the newly mandated 4.0 bar turbo boost restriction imposed by the FIA. The FIA’s mandate was a response to unrestricted turbocharging prior to 1987. Designer Steve Nichols noted that the engine’s twin plenum chambers, one for each bank of cylinders, and the 195L fuel tank size limited how low the bodywork could be positioned at the rear of the car. This limitation would be alleviated with the adoption of the smaller Honda V6 turbo and a reduced fuel tank capacity of 150 litres in 1988.
The MP4/3’s specifications included a weight of 150 kg, a 90° V6 turbo engine configuration, a bore of 82 mm, a stroke of 47.3 mm, four valves per cylinder, a displacement of 1.5 L (1,496 cc), and a maximum engine speed of 12,300 rpm. The engine produced a power output of 634 kW (862 PS; 850 hp) and 467 hp/L.
Alain Prost secured three wins for McLaren with the MP4/3 at the Brazilian, Belgian, and Portuguese Grand Prix. Prost’s victory in Portugal was notable as it made him the driver with the most wins in Formula One history at that time, surpassing Jackie Stewart’s record of 27 wins. Stefan Johansson achieved several podium finishes, but was replaced by Ayrton Senna for the 1988 season. Despite the successes, McLaren finished second in the Constructors’ Championship with 76 points.
During the 1987 season, several teams encountered issues with the FIA-mandated pop-off valve, which sometimes activated below the 4.0 bar limit, reducing engine power. McLaren circumvented this issue by setting their TAG turbo’s boost limit to 3.6 bar, which also improved fuel economy.
The MP4/3 competed during a period of increasing concern over the power of turbocharged engines. In response to the escalating horsepower figures, the FIA further reduced turbo boost pressure to 2.5 bar in 1988, aiming to level the playing field with naturally aspirated engines. Turbocharged engines were then banned completely in 1989.
The MP4/3 was the last McLaren Grand Prix car to be powered by the TAG-Porsche engine. Its successor, the MP4/4, would usher in a new era with Honda power. A sixth chassis, designated the MP4/3B, was built as a test mule for the Honda turbo engine. The MP4/3B was tested by both Prost and his future teammate Ayrton Senna, and proved instrumental in the development of the MP4/4, which would become the most dominant single-season car in Formula One history, winning 15 of 16 races in 1988. The MP4/4’s success was built upon the foundations laid by the MP4/3 and the lessons learned during the development of the Honda turbo engine.
Five MP4/3 chassis were originally moulded from carbon fibre. Chassis #4 is currently on display at the Donington Museum, chassis #5 remains in McLaren’s ownership, and chassis #1 is in private hands, owned by a Porsche collector in the United States. Chassis #2 was written off in practice at the Österreichring after being struck by a deer, and chassis #3 was damaged in a first-lap accident at the same circuit. The MP4/3B is on display at the Juan Manuel Fangio) Museum in Balcarce, Argentina.
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