FreeWheeling
 

Is there a commercially available overrunning clutch I can put in my MR2? I am hypermiling and currently getting over 46 mpg with it just by coasting on hills. I could automatically do this if I had an overrunning clutch.

Saab used to have one in the old 99 but haven't heard of anyone else doing it.

Bill

By my understanding an "overrunning" clutch only grabs in one direction. You'd give up engine braking. You accomplish the same thing by pushing in the clutch.

Yes, but since it is automatic, you may get better mileage with an overrunning clutch and you don't have the wear on the clutch plate from more frequent disengagement. I would think you could make an override into the clutch so you could engage/disengage engine braking.

Maybe I'm missing something, but if the clutch only engages in one direction, how do you back up? This isn't a problem for motorcycles, but I don't think I'd want to put the thought into parking a car that could only go forwards.