Pit Limiter Button

Many modern race cars have a pit limiter button that can be pressed to toggle the pit speed limiter. On cars where this is an option you are able to bind this in the Control screen in the in-sim options. 

This pit limiter functions by preventing the vehicle from accelerating over the speed limit. Note that the limiters will not apply the brakes for you. This means that the user must brake to lower their speed enough to be under the pit speed limit. After that, the limiter will let them keep their foot flat on the throttle without going over the speed limit.

Vehicles without Pit Limiters

Many older or simpler cars do not have a pit limiter. In these cars the driver is left to maintain the required speed themselves. 

To assist drivers in maintaining the pit speed limit, the UI element that appears when you approach pit lane displays the pit speed limit, your current speed. as well as a warning if you have exceeded the pit speed limit.

Vehicles with Pit Speed Limit Feedback, but No Limiter

NASCAR vehicles are a special case. They do not have pit speed limiters, but they have very specific visual feedback to help drivers stay within the speed limit. 

For all current NASCAR vehicles the driver must be in 2nd gear for this to be accurate. 

When in 2nd gear there are a series of LEDs (or LED style UI elements) that change color from yellow to green to red. These appear when near the pit speed limit and have the following meanings:

Yellow LightsYou are under the speed limit
Green LightsYou are at the speed limit
Red LightsYou are over the speed limit

Auto Pit Speed Limiter

iRacing allows for the use of an automatic pit speed limiter. This limiter automatically engages when you enter pit lane and disengages when you exit pit lane. However, as with the manual pit speed limiter, the automatic pit speed limiter will not apply the brakes for you, and it is the driver's responsibility to enter the pits below the pit speed limit.

The automatic pit speed limiter can be used in all Official sessions that are C license rating and below, as well as in any test drive session. When creating a hosted session, use of the pit speed limiter can be toggled by adjusting the "Hardcore Level".

To enable this function, select "Auto pit speed limiter" in the Drive tab of the Options Menu. If the session allows the use the auto pit speed limiter, the text will be in black, if the session does not allow the use of the auto pit speed limiter, the text will be gray.