It was a unique Fiat built for guilty, sporty pleasure, with a mid-engine and rear-wheel-drive system fired up the car-enthusiasts imagination. At the beginning of the '70s, only a few supersport had the engines mounted between the seats and the rear wheels. It was just like a concept car built on an assembly line for those times. But Fiat considered that if that recipe worked for them, it would work well for a mass-market vehicle, such as the X1/9.
Bertone designed the wedged-shaped vehicle as a targa with a removable top. It kept the safety arch behind the cabin, over the flat rear end of the car. For the European market, the bumpers were made out of rubber. They were wrapped around nicely around the front and the back. For the U.S.-market version, the carmaker had to install bigger bumpers with chromed-metallic parts built on top of thicker rubber parts to comply with the safety regulations, but that spoiled the roadster's image.
Inside, there was room for two passengers, and it was suitable for average-height people but was considered small for the taller ones. That's why Bertone modified the vehicles' floorpans and introduced a version with more legroom after 1982. The two bucket seats were fitted as standard and covered with man-made leather, named leatherette.
Under the hood, Fiat X1/9 featured a 1.3-liter engine carried over from the Fiat 128 paired to a 4-speed manual gearbox. It was a fuel-efficient engine but could hardly make the car get to 105 mph (170 kph). In 1979, Fiat introduced a new, 1.5-liter engine paired to a 5-speed manual that could propel the little nimble roadster to 112 mph (180 kph). Not a big improvement, but still, it was better thanks to that 5-speed transmission.
Source: FIAT X1/9 specs & photos - 1972, 1973 ... - autoevolution. https://www.autoevolution.com/cars/fiat-x19-1972.html
Images: Fiat; Carrozzeria Bertone s.p.a.
Pictured Above: Fiat X1/9 (Bertone), 1972–1978