Powered Third Wheel Speculation
 

There have been a few threads about the possibility of converting a front wheel drive car to be a three wheeler and today I was considering variations on that idea. If the third wheel had its own small engine with a single gear set for cruising speed and connected via an overrunning clutch, you could turn off the main engine and get around the big engine running at partial load efficiency problem. No need for a differential either. For a light car the engine wouldn't have to be very large and you could even consider making it a diesel. Controlling both engines might be a little interesting, although the overunning clutch would simplify this somewhat. Just an amusing speculation.

I guess that would be easy to do with a motorbike back end... some 100cc scooter or something. I have heard of folks rigging a Kohler diesel like that.

Needn't be a three wheeler to do it though. Could be a FWD car that has an AWD version you can steal the rear axle and driveshafts from and use that for power transmission from a motor mounted under the back end somewhere. Though that's a good way to make a through the road hybrid too.