You simply ran out of room to catch and pass him if you only got to 80mph. Even with the Superman Button under the throttle clicked on I am estimating it would take my SRT 2 seconds to go from 40mph to 80mph and since you already gave him this much headstart to begin with then it is not surprising that you can only get even with him before shutting off.
Don't worry about it.....you had fun did you not?