Cars can't be modeled with Amapi Pro 7.15 NURBS. Otherwise, there would be NURBS tutorials everywhere for modeling cars using Amapi Pro 7.15.
Polygon modeling is really the only way to model a car properly. See
http://www.cgtalk.com/showthread.php...ge=1&pp=15 for a method that works great in Amapi 7 (any version).