Do you know where the airflow separates on your vehicle? They placed them slightly forward of this region to retard the separation. If you don't test for the separation point and place the VGs too far forward of the point, they will only cause more drag because the vortices aren't doing their job. The VGs create drag while creating vortices. And if you place them behind the separation point you aren't doing anything but adding weight to your vehicle.
I don't want to come off rude. I'm sorry. Aerodynamics is a passion of mine. I want to share it with everyone!
