At the 1993 Formula One Grand Prix held in Monte Carlo, Italdesign introduced a new, slightly redesigned version of the C2 called C2 Spider. The car had removable glass panels instead of the semi-gullwing doors featured on the coupe, turning it into a roadster along with a modified engine cover. The removable parts were housed in the luggage compartment in the car's front and could be quickly reinstalled. A roll bar in the car's color was fitted to reinforce the chassis to compensate for the loss of removable glass panels. The intake manifold of the engine was redesigned to allow for open-air operation.
The car was fitted with a 5.7-liter V12 engine shared with the 850CSi. The engine generated a maximum power output of 380 hp (283 kW; 385 PS), a 6-speed gearbox was installed instead of the 5-speed gearbox of the coupe to better cope with the increase in the power.
Sources: bmwblog.com, OldConceptCars.com, Wikipedia