I did similar for FOX Racing. I watermarked the shot and sent an invite to FOX Racing. The image was reviewed but they declined. I at least got them to look at it. It would be no different for others. Make a list of potential publications and Porsche themselves. Having a gallery for them to view would be ideal. If you don't have one, I would send a watermarked jpeg with a copyright disclaimer in that email, so if someone does steal it and manipulate it, you have record. also make sure your metadata is complete. Finally, if you are serious about offering your images for commercial sale, get the right usage rights and market rate compensation. Stipulate credit, but do not give your image up for your name in lights. Register the image(s) with the ECO.
They are good photo's, good luck.