Spirit decided to continue in Formula One for 1984 with Hart turbocharged engines. Inititally twice world champion Emerson Fittipaldi and moneyed Italian Fulvio Ballabio were slated to drive. However Fittipaldi left to find a drive in Indycars after finding the machine uncompetitive and Ballabio was refused an FIA Super Licence. Instead Italian Mauro Baldi found funds and was nominated as the team's sole driver, Stefan Johansson being released as he could not find the funding to continue. The 101 was a neat but underpowered car and Baldi struggled to move away from the rear of the grid. Jean-Louis Schlesser had planned to take over from the third race before the threat of litigation from RAM Racing, as he still owed them money.

The first version of the car, was presented largerly incompleted at the Italian Grand Prix and didn't race during the season.

In 1984 the first chassis was adapted to house the Hart 415T engine and become the "101B", with new sidepods. Later a new better build chassis was build and debuted at the 1984 San Marino Grand Prix, while the first was later newly modificated as "101C" to adopt the Ford Cosworth DFV (third type of engine in few months), with the previous year side pods, and after the Detroit refitted with Hart engines to be used as T-Car.

...
Wikipedia