Every car in Forza Horizon 3 is assigned a Performance Index (PI) and belongs to a specific car class. The PI is a numerical representation of a car's overall performance, ranging from 100 (slowest) to 999 (fastest). Car classes categorize vehicles based on their PI:
- D Class: 100-399 PI (Entry-level, classic cars)
- C Class: 400-499 PI (Older sports cars, some sedans)
- B Class: 500-599 PI (Modern hot hatches, classic muscle)
- A Class: 600-699 PI (Performance sedans, sports cars)
- S1 Class: 700-800 PI (Supercars, high-performance sports cars)
- S2 Class: 801-900 PI (Hypercars, extreme performance vehicles)
- X Class: 901-999 PI (Concept cars, highly modified race cars)
Most events in Forza Horizon 3 have car class restrictions, meaning you can only use cars within a specific PI range. When upgrading a car, its PI will increase. The goal is often to maximize performance within a given class without exceeding the upper PI limit. Understanding these classes is crucial for selecting and building appropriate vehicles for each race.