[Limex]

There is not one single way of doing this. Each game mode has it's own car system and it's own way of working. For anybody to be able to help you, you need to instruct us what GM you're using (and a link to the download thread to make our lives easier).

Ideally you would post this question directly in the thread of the GM and somebody who checks that and has knowledge of the specific car system would help you.