Well ya got part of it right with IMSA, but it isn't that simple. The goal is to balance the performance, not penalize anybody.
Some people will always miss the fundamental rule. The rule has been proved many times and it is If you let teams go without any boundaries, the racing series will eat itself in a short time. For example Can-Am from the mid 60's proved it with 1500 HP cars.
Anyway, here is how IMSA's BOP works.
IMSA’s technical team, led by the IMSA Technical Committee (ITC), collects and analyzes a wide range of data to assess each car’s performance. This includes telemetry from onboard data loggers (measuring things like speed, throttle position, and torque), timing and scoring data, wind tunnel tests, engine dynamometer results, and even real-world race performance. For some classes, like GTP and GT cars, advanced tools like driveshaft-mounted torque sensors have been introduced in recent years to measure power output directly at the wheels, providing a more accurate picture of a car’s capabilities.
Based on this data, IMSA adjusts specific parameters to balance the cars within each class. These adjustments can include:
- Weight: Adding or removing ballast to alter a car’s minimum weight.
- Power: Restricting engine output via air restrictors (for naturally aspirated engines), boost limits (for turbocharged engines), or fuel flow rates.
- Aerodynamics: Modifying wing angles or other aero elements to adjust downforce and drag.
- Fuel Capacity: Changing tank size or refueling rates to influence stint length and strategy.
The aim is to keep all cars within a tight performance window—typically 0.3% for GTP and GTLM classes (about 0.3 seconds over a 100-second lap) and 0.5% for GTD (0.5 seconds).
This ensures close racing where no single manufacturer dominates due to raw performance.