This is used when children are misbehaving in the car. A parent will threaten the children with the phrase, "I'll turn this car around right now!" so that the children will stop behaving in a bad manner. Normally, this statement is used when the children are going somewhere that they are excited about, such as a playground or another fun activity. Turning the car around means that the parent will turn the car around to return home and there will be no fun that day. Does this answer your question?

Hello Yi Wen, The usage of the sentence and its meaning can be different depending on the situation. One such situation is when children are misbehaving which makes their parents mad. For example, the family is going to see a children's movie at the movie theater such as Finding Nemo. The child won't stop yelling in the car. His mother has had enough of his behavior so she gives him a final warning. I’ll turn this car around right now (if you don't stop). I mean it!