I'm just spit-balling here, but what about a GPS data-logger. It'd be a shame to limit the car so much in case you wanted to drive it, or your son decided he wanted to get into a VERY good hobby like drag racing. I know there are GPS trackers on the market that will log any trips the car takes. I'd see if any will log the cars speed and acceleration. Just check the log every night to see if your son has been honest and responsible. If he gets a little "hoonish" you can discipline him accordingly. To me something like that would teach him a lot more about responsibility and restraint then limiting the car.

 

In fact, just did a quick Google search and found exactly what you'd want if you wanted to go the GPS tracking route: How To Track A Teen's Car With GPS