My car does what?

When I came back from a work trip recently, hubby turns to me and says, "Your car has a restrictor thingy in it, that stops things from going too fast when you max out the revs on the car".
Now, he didn't really say that. But, something like it. Car talk. Of which I know nothing about.
All I heard was RESTRICTOR and MAX, and realized that if he's maxing out the car (no matter what it is), and maxed it out so much that he found some kind of restrictor that I know nothing about... well, I simply don't want to hear about it! It is MY car after all.
Then I saw this on the internet...

I'm not an over protective dad by any stretch of the imagination, but I can totally see where this guy is coming from.