Photographing black on (predominantly) black is difficult if you have something else in the frame...like the red car. For the most part, you will have to over expose the black car, and that will wash out the color of the red car. Here is an example...the over exposed black car washes out the orange:

The only way to get around that is to photograph the cars on a lighter surface than the black car...that way you can easily see the edges of the car, and your brain fills in the rest. Also, to avoid the multiple reflections, paint a plain sheet of glass black on one side...works really great! (see example photo)