What you do:
Choose an rpm (revolutions per minute) setting.
Factors to consider:
You may have built an engine that is capable of high rpms, but loses a lot of power as it reaches these high rpms. This loss of power could occur due to air turbulence at air speeds close to the speed of sound. It may make your car faster to limit the rpms your engine can reach.
In real life, rev limiters prevent engine damage. Real engines may have parts that cannot handle the stress or speeds of higher rpms. For example, some engines are capable of 8000 rpm, but the springs on the valves do not pull the valve out of the way fast enough at that rpm. If the engine were to reach 8000 rpm, the piston would smash the valve, causing extensive damage to the engine. A rev limiter set at 7000 rpm prevents this from happening.