I'd like to comment on some of you process.
First off, draw a bit larger. It looks like you're trying to fit a lot of details into a very little amount of room. A bigger paper will expand the space between those details, making it look a lot more "real". Next, before you do the first line drawing (before filling in any parts), select the right strength pencil for those lines. If you know exactly what your drawing (you know you won't need to erase a lot), take somehting around 3H (not harder than that, if you need to erase, the hard pencil will make grooves in the softer paper, and when you fill everything in, you'll see white lines where you erased), but if you think you're gonna make mistakes, go softer, HB or so; the softer graphite will obviously be darker on paper, but erasing won't leave any permenant damage. Next, when you fill everything in, use smudgers to smooth out the now-textured surfaces. When you run everything over with the smudgers, it'll also lighten up those lines if you used the softer pencils (using either the softer HB or harder 3H, your lines will be less obvious in the end). Oh, and go over some of the lighter spots with an eraser when you're done, in most cases adding constrast helps, and it certainly would here.
Judging by that drawing of yours, you're close to achieving failry good photorealism. Just draw exactly what you see in the referance picture, and take time on the details, and you're on the right road. Three or four more drawings and you'll have progressed a lot. You've got a decent eye in proportions/perspective, the S7 only has minor problems (I'd definitely lighten up that far side shoulder, it should be next to invisible, if there at all). When you're done your line drawing, flip the paper backwards, put it up to a light, and look through the back. Now your drawing is reversed, and you'll see all of your mistakes. It works wonders, especially if you've been sitting there doing the line drawing in one, long sitting.
Oh and one last presentation thing: I wouldn't recomend doing a horizon line (leave it out, just make the undershadow a bit larger), but if you really want it there, please-oh-please, use a ruler to draw it. Right now, it's really pulling down the whole thing.
Over-all, good job. Once you figure out how to to get nice, even tones with the smudger, you'll be able to move on to making white or silver cars, which look really impressive when done right. In short, use larger paper (nothing absurd, but nothign in the single digits for inches) and buy smudgers (fingers work, but are less effective, smudge in sweat/dirt, get messy fast, and smudgers cost 2$ for a set of 3).