Lamborghini Diablo VT Roadster
The Diablo VT was introduced in 1993. Although the VT differed from the standard Diablo in a number of ways, by far the most notable change was the addition of all wheel drive, which made use of a viscous center differential (a remodified version of LM002's 4WD system). This provided the new nomenclature for the car (VT stands for viscous traction). The new drivetrain could direct up to 25% of the torque to the front wheels to aid traction during rear wheel slip, thus significantly improving the handling characteristics of the car.
Other improvements debuting on the VT included front air intakes below the driving lamps to improve brake cooling, larger intakes in the rear arches, a more ergonomic interior with a revised dashboard, electronically adjustable dampers, four-piston brake calipers, power steering, and minor engine refinements. Many of these improvements, save the four-wheel drive system, soon transferred to the base Diablo, making the cars visually nearly identical.
The Diablo VT Roadster was introduced in 1995 and featured an electrically operated carbon fiber targa top which was stored above the engine lid when not in use. Besides the roof, the roadster's body was altered from the fixed-top VT model in a number of ways. The front bumper was revised, replacing the quad rectangular driving lamps with two rectangular and two round units. The brake cooling ducts were moved inboard of the driving lamps and changed to a straked design, while the rear ducts featured the vertical painted design seen on the SE30. The engine lid was changed substantially in order to vent properly when the roof panel was covering it. The roadster also featured revised 17 inch wheels.
Source: Wikipedia, 2012