If you are going for realism, I suggest that you try using Nurbs or Sub-D's. Also don't be afraid to take the model further than your drawing, like putting details like a vents in and adding whatever it is that is going to be propelling your vehichle forward. It needs more Form and Function detail, that is what I think Pure was trying to get across. There are many different ways that the modell can be advanced upon. You should check out some car magazines, they might help you expand.
When I sketch Ideas, I tend to draw things less detailed and often it reflects in the work, don't be afraid to take it further.
Best of Luck, hope I was helpful.