Your vision on this piece is really cool...to do the portrait, initials and car.
The first thing that strikes me here is the difference between the rendering of the figure and the car. It looks as if you took much more time with the figure, especially the face, and then rushed through the car. The proportions on the face are pretty accurate, but the proportions on the car are not. The face looks rounded to me because you used a lot of good subtle value changes, where as the car looks rather flat.
The car almost looks like it is tucked into the drivers shirt, with his jaw extended over the windshield. So you need to push the figure back while bringing the car front. If you draw all of the mans head, it will push him back in the composition. By cropping off the top of his head, you bring him too far forward. There is not enough difference between the grays and strokes of the mans jacket and the hood of the car. You need sharp lines and value changes in that car to make it appear different than the jacket. The blackened out windows look out of place, too. Again, you need to spend more time on the car.
The jacket has a nice feel to the cloth...it looks very believable. The car, then, needs to have sharp lines with harder value changes to come forward.

All in all it's a great idea and a good drawing. It needs more care and attention to be a great drawing. Take your time on the car! You obviously have talent, and you will be rewarded with a great drawing if you invest the time!