The MP4/5 was developed in response to a regulatory shift in Formula One. 1989 was the first year where naturally-aspirated engines were compulsory for all teams following the banning of turbocharged units at the end of the previous season. Honda developed a 3.5-litre V10 engine throughout 1987 and 1988 to meet these new requirements. The design team was led by Neil Oatley, with contributions from Steve Nichols, Tim Wright, Bob Bell, Mike Gascoyne and Pete Weismann, under the overall leadership of Technical Director Gordon Murray. Osamu Goto was the Honda F1 team chief designer for the car's engine. The MP4/5 was loosely based on the highly successful MP4/4, aiming to build upon its predecessor’s strengths with the new engine formula.
The MP4/5 initially utilized the Weismann Longitudinal Transmission from the MP4/4, while the later MP4/5B featured a new Weismann Transverse Transmission. The car’s monocoque was constructed from carbon-fibre composite materials produced by Hercules Aerospace, with interchangeable aerodynamic parts attached to the chassis. Early versions of the car suffered from imbalanced handling in fast corners, which Honda addressed by improving the smoothness of the throttle response. McLaren initially used brakes made in-house before switching to Brembo brakes. Alain Prost requested a richer fuel mixture for his engine, believing it better suited his driving style. The car featured a two-way radio system for communication between drivers and the pit wall, but early iterations experienced interference with the engine control unit sensors, requiring a design change. The engine's lubrication system also presented issues, particularly in wet conditions, prompting modifications at subsequent races. Towards the end of the 1989 season, Honda introduced two new engine revisions, one optimized for high-speed circuits and another for slower tracks or wet weather. The MP4/5B, introduced for the 1990 season, featured redesigned front and rear wings, reprofiled rear bodywork around larger radiators, and all-new venturi tunnels on the rear floor.
The MP4/5 debuted in the 1989 season with Ayrton Senna and Alain Prost as drivers. Senna and Prost secured ten victories during the season, six for Senna and four for Prost. Senna scored fifteen pole positions, thirteen of them himself, equalling his record from 1988. At the Mexican Grand Prix, Senna achieved his 34th career pole position, breaking Jim Clark’s long-standing record of 33. Despite Senna winning more races, he finished 16 points behind Prost in the championship due to accidents and mechanical failures, resulting in fewer points-scoring finishes. McLaren’s combined points total secured their second consecutive Constructors' Championship. A version with the transverse gearbox debuted at the British Grand Prix, where Prost won, but Senna struggled with the new gearbox. The championship was ultimately settled at the Japanese Grand Prix, where a controversial collision between Senna and Prost resulted in Senna’s disqualification and Prost winning his third World Championship.
For the 1990 season, Prost moved to Ferrari, taking designer Steve Nichols with him. The MP4/5B continued with Senna and Gerhard Berger as drivers. Senna and Berger took the fight to Prost and Nigel Mansell, winning six races and securing another Constructors' Championship for McLaren. The MP4/5B demonstrated strong qualifying pace, frequently placing both cars on the front row, particularly at power circuits. However, the car sometimes struggled against the Ferrari 641 in the races, especially with heavy fuel loads. The 1990 Japanese Grand Prix saw another collision between Senna and Prost on the first lap, which secured Senna the championship as Prost was unable to continue.
The success of the MP4/5 and the competitive advantage of the Honda engine did not trigger any immediate rule changes.
Gordon Murray, the designer of previous championship-winning cars for McLaren, retired from Formula One after his work on the MP4/5 to focus on McLaren’s road car project. During the 1990 season, McLaren developed a test mule, the MP4/5C, for Honda’s new V12 engine, intended for use in the following two seasons. This engine was tested by McLaren’s test driver Allan McNish and showed promising reliability at an early stage of development. The MP4/5B was later featured in several video games, including Gran Turismo 3, F1 2019, F1 2020, and Automobilista 2. Seven-time Formula One World Champion Lewis Hamilton drove Senna’s MP4/5B at Interlagos ahead of the 2024 São Paulo Grand Prix.
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