Pininfarina's wind tunnel tests based on the FIAT '1' segment for car aerodynamics, were the ultimate basis of the development of cars in this connection such as the UNO (1983). This is revealed by an illustrated literature survey. Thus reduction of the vortex flow at the rear of the vehicle, and also of transverse vortex flow, has tended to generate a ring vortex mechanism. This latter mechanism can further reduce drag by ca. 30% or more compared with vehicles at present on the road. This main possibility of improving aerodynamics can be supplemented by improved internal flow, especially ventilation, greater directional stability, reduced vehicle noise.
The evolution of car aerodynamics / Morelli, A.. - In: ATA. - ISSN 0001-2661. - 41:1-2(1988), pp. 54-67.