Why Dave is just an Idea, like any other ideas that sometime is was just crazy for everyone else till become a fact. By now if I can ($ wise) I whant to try this my self.
Your first post was pretty disjointed. You basically said hook an autotransformer up to the car. So the question came back, what is a autoformer going to do with 12V DC?
I now understand (I think) what you are saying. Use an inverter but clean up the output. Since an autoformer only has one winding across the line, I don't think it will clean up as well as your other suggestion of an isolation transformer. That might do it, but X10 is very critical of noise on the half cycle and any distortion.
I did find a pure sine wave inverter on eBay where they stressed the output is a clean, undistorted output.
