A realistic script must simulate the mechanical journey from the engine spark to the rubber hitting the road. Engine Torque Curve
The difference between an arcade game and a simulation is how the tires handle. You need to script "Slip Graphs."
Tires are made of elastic rubber. They must slip slightly against the asphalt to generate grip.
Calculate horsepower dynamically based on the current torque and RPM. Transmission and Gearbox