Following the turbulent period of the twin-chassis Lotus 88 controversy and the limited results of the Lotus 87, Chapman elected to go back to basics for the 91. The car drew inspiration from the Williams FW07, one of the most successful ground effect designs of the era, as well as lessons from Lotus's own 88 programme. The goal was a straightforward, reliable, and well-sorted car that could compete against the increasingly powerful turbocharged machinery on the grid.
The 91 was constructed from carbon fibre and Kevlar composites, making it the third Formula One car to race using these materials, after the McLaren MP4/1 and the Lotus 87. Its lightweight chassis gave it a competitive edge against the turbo cars that were beginning to dominate, since the power difference was partially offset by the naturally aspirated car's lower weight. Power came from the Ford Cosworth DFV V8, paired with a standard Hewland gearbox. Cosworth developed a dedicated short-stroke version of the DFV specifically for Lotus's use that season.
Aerodynamically, the sidepods were full-length units extending to the rear of the car in order to maximise the ground effect downforce that was still permitted under 1982 regulations. The 91 also became the first Lotus chassis to use carbon brakes, improving braking performance significantly following the lead set by Brabham. The car was, however, acknowledged to be pitch-sensitive and demanding to drive as a result of its aerodynamic sensitivity.
Elio de Angelis was the team's primary driver and found the 91 most effective on high-speed circuits where the ground effect aerodynamics could generate their maximum benefit. Hockenheim, Monza, and the Österreichring all suited the car. At the Austrian Grand Prix, de Angelis produced a memorable performance that culminated in a final-lap victory over Keke Rosberg's Williams, a result that encapsulated both the 91's potential and the competitive tightrope that normally aspirated cars were walking against the turbo-powered opposition.
That Austrian win was the last Formula One race won by a Lotus car before Chapman died of a heart attack on 16 December 1982. Consistent results from de Angelis, combined with a podium finish by Nigel Mansell, secured Lotus fifth place in the 1982 Constructors' Championship — a meaningful recovery for the team.
The 91 also served as the development basis for the Lotus 92, which became the first Formula One car to race with active suspension. The 92's system used hydro-pneumatic valves and early on-board computers to control ride height and suspension behaviour, though the technology remained partially experimental at that stage.
The Lotus 91 was retired at the end of 1982 when ground effect aerodynamics were banned for the following season. It was replaced by the team's first turbocharged car. The 91's campaign stands as the last competitive chapter written by Chapman himself, whose death closed one of the most influential eras in Formula One engineering history.
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