Car testing
This article presents in-game methods for obtaining accurate performance stats of Stunts cars. While several relevant stats can be predicted from the car parameters or obtained by processing repldump output, carrying out tests within the game is often faster than such analytical methods — not to mention more fun!
Top speed
Two different, equally important notions of top speed apply to Stunts cars. The flat track top speed is the speed the car can achieve by accelerating on a long enough straight, with no jumps or obstacles. It corresponds to the top speed of real cars, and is limited not only by the torque curve and gear ratios, but also by aerodynamic drag. However, jump boosting and powergear, in game versions having such effects, allow Stunts cars to overcome the limit imposed by drag and reach their real top speed.
Flat track top speed
The easiest way to get a car to its flat track top speed usually is accelerating for a few minutes on a long, fully banked track, taking care to skid as little as possible on the banked corners. That is best done by driving in a counterclockwise direction, to take advantage of left corner bias in game versions that have it. Once it becomes clear there is no more speed to be gained, the test can be ended by releasing the accelerator (to avoid gaining speed by jump boosting) and crashing the car against the outside wall of the banking; the impact speed from the evaluation screen can thus be used as the test result. A few cars have an overdrive final gear which doesn't actually bring extra speed on a flat track; if that looks plausible for the car being tested, it is a good idea to check the flat track top speed at the gear below the top one.
Flex-PG and anti-PG
The banked track method doesn't work well for flexible powergear and anti-powergear cars, as, once they get close enough to their flat track top speed, the slightest vertical movement on the banked road will trigger flex-PG or anti-PG, compromising the test result. An alternative method for such cars is using a very large square of fast grass as a completely flat "track". 24 x 24 tiles should suffice for most cars, assuming there is enough fast grass area inside of the corners of the square. To minimise skidding, it is recommended to drive smoothly on a circular trajectory, using as much of the width of the "track" as possible.
Real top speed
The real top speed is quite a bit easier to find in a test: just accelerate through a long stretch of track with many jumps, without releasing the accelerator while on air, and crash or sink the car at the end. To make landing impacts more predictable, it is a good idea to use longer jump distances in the latter parts of the test track. The only needed precautions are releasing the accelerator while climbing ramps (but not in mid-air!) with anti-PG cars, and keeping an eye for landing slowdowns on cars susceptible to them (such as the Nissan Skyline).
