Lotus 88

Information

One of the most aerodynamically innovative car in the whole F1 history. In the 1970s teams heavily relied on ground effect. Speed increased sharply but safety didn't, so FIA banned side skirts, a main part of ground effect car which can seal the area under the car, also put a new ride height rule to reduce ground effect.
Collin Chapman wouldn't give up ground effect, which had brought Lotus glory in the past decade. So he came up with an ingenious idea, twin chassis. Lotus 88 has 3 parts, a carbon monocoque, a lower chassis including sidepods and an upper chassis. The lower part holds the car's weight and the upper bears aerodynamic force. The two chassis parts were sprung together, so when speed builds up, the upper part is pressed down by the increasing downforce, and the ride height decreases. As a result, the area under the car was sealed, same effect as side skirts. So Lotus 88 didn't need wings to produce massive downforce.
Both Mansell and de Angelis liked the handling, but other teams protested against this design - it could be dominant. So FIA announced that Lotus 88 was illegal. There was a fight between Lotus and FIA, and FIA even threatened to remove Lotus from the Championship standings. In the end, Collin Chapman gave up his genius design. Lotus 88 never raced or even never finished its development. How it would perform remains a mystery in F1 history.