[EcoVan]

Is this the rule of thumb simply " at most covering the low hanging component of the vehicle" or some other mathematically derived number? I could certainly see in my mind's eye that a shorter air dam would shield the low hanging components from creating drag if the air stream is sculpted downward by the shape of the air dam or valance. This would allow greater ground clearance but still maintain the gains possible. The cross sectional view of the airdam/valance suggests it is creating downward velocity with the sloped section and then the smaller flat air dam portion is at the bottom.....Maybe the blast fence as described previously.

Unfortunately, its going to be a few weeks before I can test this installation, as the van needs a new sensor and some front end work. However, I have nearly 80,000 miles of experience already with it, so a base is already established. Also, with my experience with my 93 escort, the air dam by itself did'nt seem to be particularly beneficial and neither did smoothing out the front underside. However, when the belly pan was attached to the bottom of the air dam, that was when the magic happened. I suspect that this configuration allowed the cooling air being pushed/pulled into the engine compartment filling the vacuum behind the air dam, greatly reducing it drag.

I already started mocking up a belly pan that will attach to the bottom of the van's air dam and close up the front of the front wheel wells.