Not sure how Low & Mean's interstate box truck mission relates to NASCAR 200 MPH competition. Suspect there may be different dynamics at play between diets of: hauling loads at 75 MPH & creeping urban traffic, VS. pedal to the metal NASCAR racing & parade laps under flag. If only b/c NASCAR rules allow a maximum 50 sq. in. opening for cooling. Estimate the opening on my Econoline is over 600 sq. in.


Sure "Airdams work." at 200 MPH & NASCAR wants 1500 lbs of down force. Maybe not so much grunting light to light, cross town, at crunch time?

Seems like Low and Mean's 2nd pic is extremely close to the ground. Impression is of being a Low Rider, or hints on a sizzling Summer day, hauling a respectable load, it might get hotter than normal underneath, if caught in traffic.

Maybe I should post pics of "simple examples" of irregular surfaces many vehicles in my area drive over to show airdams get smashed?

 

As I'm looking at the OP's photos I don't see any reduction in the grill area so its highly unlikely such an addition disrupts or affects air flow through the radiator and entire engine bay. While aerodynamics are part and parcel to every type of racing vehicle it doesn't typically apply to street driven cars and trucks.

IIRC most modern day cooling systems are designed to withstand ambient temps approaching 140* F---most likely believing they may be used in harsh jungle, tropical or desert settings. They are tested in a heated paint-booth like facility with nothing more than the on-board (radiator) fan pulling air across the radiator.

OP's air dam addition is probably just fine as is, no detrimental effects to the van's operation at all.

 

Perhaps I've not been clear discussing air flow thru radiator & tunnel VS. extensive airdams "keep air out from under the vehicle"-as it relates to MPG. NASCAR speeds need Down Force, often see figures like 1500 lbs of aerodynamic down force. They do it for cornering & to prevent going airborne, not MPG. Don't think many working box trucks want to sacrifice load capacity, trying for aerodynamic down force.

The blunt "Big front bumper" significantly increases an already "Big" frontal area, which significantly increases air drag. Air drag is NASCAR's enemy, turning races into a drafting competitions, but they don't haul cargo. In terms of splitting the air, a box truck is like a wood mallet & NASCAR like ax. Don't forget NASCAR's new 50 sq in maximum opening for cooling.

On a high ground clearance truck the "Big front bumper" significantly decreases air flow underneath. Econoline typically has 4 very hot, heat shielded, top & bottom, catalytic converters. Cats rely on normal air flow to dissipate heat. To some degree the muffler, exhaust system & tranny are cooled by normal air flow. We know how NASCAR disperses intense exhaust heat.

As I'm looking at the OP's photos I" see large nonstock heat exchangers added behind the OEM grille & behind the nonstock mesh grille added right where center of the rather formidable steel OEM bumper had been.

What's that 'Big front bumper' made of anyway, fiber glass? Is it actually a continuous structural, frame rail to frame rail bumper, OR a couple of corner bumperettes supporting an aerodynamic fascade, w/only a skin of FG linking the ends of frame rails?

Did NHTSA/DOT crash test/mandate specs/certify front bumpers on Econoline?

In another thread OEM cooling fan capacities got discussed. Figures as high as 8,000-12,000 CFM were cited. If extensive airdams "keep air out from under the vehicle" wouldn't they also tend to keep air under the vehicle from getting out?

Could be a challenge creating the negative pressure underneath mentioned w/8,000-12,000 CFM fan pumped in thru 600 sq in opening.