I think you should check out the link that rino.mexican posted...I know it costs a little but you will see big benefits in your drawings from a proper perspective set up and knowledge, know dont get me wrong it looks great and i think you definitely have some great skills.
i think you should spend you time practicing drawing cubes, cylinders, spheres, ellipses. LEARN perspective. your perspective is way off on every car. if the whole doesn't look right, it's useless to add tons of details to it. first you have to learn the basics, the rest, is just detail...
