I'm just not certain how they will effectively enforce FastPass return times on a ride like Racers that goes down CONSTANTLY and already requires stringent planning to even GET a FastPass in the first place. People are lining up for an hour or more (before entry) to even CLAIM a FastPass. It's not like you have much (or any) choice regarding your return time. If that FastPass they finally get conflicts with their other plans (restaurant reservations, tours, etc.) OR happens to be during a time that Racers is either down, or has recently been down (resulting in ultra-long lines), I think Disney might have a riot on their hands if they denied those guests later entry.
I've detailed my experience elsewhere, but the ride was only running one day of our five early entry at opening and we heard of downtime just about every day we were in DCA (six total), including two days where the ride was basically non-functioning the bulk of the day. Twice we were caught in the "it broke down" lines (where they cleared queues) and multiple times when we came back to Carsland to use our FastPass, the FastPass line was backed up to the point it was a 60-90 minute wait, per cast members. (Usually due to prior ride downtime.) One day we tried to use FastPass return 4 different times during the day, before finally giving up, since we never found a FastPass line less than 45 minutes. Though, if that had been our only day at DCA, or we hadn't yet ridden, we might have waited. Based on what I've read before and since our trip, I believe our experience with this ride's reliability was the norm, not the exception.
I don't want to arrive at the gates an hour before opening, standing in line for FastPasses for an additional 45-60 minutes and then also stand in a 90 minute FastPass line to use them. Just ridiculous!
I will add though, that after "losing" that set of FastPasses, we always rode as soon as we were able, assuming the ride was up and running, since we never knew if that would be the case later or not.