Has anyone done anything with designing & placing some sort of underbody/engine shielding for any of our trucks?
Sort of like what is under my 2012 Toyota Highlander protecting the oil filter, oil plug, & etc..
Thank you for any kind of information/advice you may offer!

 

No I have not, but be careful, you can shield off the normal air flow to help keep it cool. Don't you have more heavy steel items below the oil filter? Are you off roading to the point that you need to shield the oil filter? Just curious.

 

Hmm?!?!? No, I don't expect to do any, or minimal off roading. I just thought that it would be more fuel efficient with less drag from the old fashioned undercarriage open like they were.
I was only thinking in terms of the radiator being efficient enough to adequately handle heat concerns.
Hmm?!?!! Any other thoughts?

 

Well you know you are driving a none aerodynamic brick down the road anyway and IMO a belly pan is not really going to help any. Think about overall vehicle weight reduction, tires sizes, and rear end gearing or a 5 spd swap to get a few more MPG.

 

Get rid of big mirrors, running boards, mud flaps, outside sun visors, big cb antenna's, box covers, oversize tires, any tire that has to much offset. It all ads up pretty fast for poor mpg's. If you think something as silly as a cb antenna or a towing mirror hurts much try holding one out the window going 60 mph. Tire pressure another big mpg factor.

 

A complete shield covering the whole underbody bumper to bumper with cut outs for oil changes, etc, an exhaust venting, made of 1/2" steel plate would do wonders for handling, like keeping the guide pin in the slot at speed, It might require some engine upgrades, just to move it up the mountain. One could add scoops for cooling, etc, maybe NACA ducts for low drag.. We used to do it with slot cars, but we used brass plates.

In all seriousness though, once did some experimenting on a police car, used a piece of aluminum cut with a sabre saw from a discarded bent large interstate highway sign (provided free by VDOT after a TT crash knocked it's poles down) to block under car air from catching the big void from trunk floor to lower lip of the rear bumper under a '98 Crown Vic. It was bent but I laid it in the driveway and run over it with my '77 truck to flatten the bend in it. One could not see it unless getting down on knees and looking up. Also reinforced the black plastic original under radiator front chin spoiler. The mods helped noticeably at triple digits, I painted them black, run them for a few months ... but then one day the car was up in the air on a lift and getting an oil change when my Sgt. stopped by for coffee & walked into the bay area to say hello. He just had to look under my marked police car way up there on the lift too. He did subtly suggest that the rear piece not be there when car was next inspected. Was a shame too, the mod was good for a few extra mph on top.

An often then seen, visible mod on CV police cars was what they called "The Bumper Mod" using big zip ties called "Flexi Cuffs" to cinch up or pull the lower lip of the rear bumper up as high as possible towards the floor pan of the car. It helped both in letting trapped air out at speed and in preventing the rear bumper being torn by it's snagging roadway features on dip transitions. I think my aluminum sheet deal was better aerodynamically though.

Yeah, I think there might very well be some gains on a F-150 just in hiding the large void under the bed but above the axle and ahead of the rear bumper from under-truck turbulence. There are practical considerations, like spring / shock / axle / drive shaft movements and exhaust-gas egress from pipes. Even up front, if some considerations were involved for exhausting under hood air that came in the radiator and access to service items were included, there's gain there too. Even Ford saw reason to incorporate chin spoilers and under truck drag reduction, though subtle, in later years.

You'll never kill all the drag as any air displacing object moving through air will have some drag as a vacuum is created by the movement, and the faster the movement, the higher the drag as air must then move to fill the void. NASCAR cars have been found to have hundreds of hours devoted to massaging of frame to floor joints and removal of ledges, etc.

A tear drop has a taper at the rear that will aid or guide the back flow of air into the void created by the falling tear drop.

 

If aerodynamics is the primary concern then perhaps some of the folks here with lowered or "slammed" trucks will weigh in on this. As Rich pointed out, engine heat needs an exit path. Louvers in the inner fender panel and/or hood might be all you need after a radical lowering that removes the need for a belly pan. Of course belly pans can be louvered as well but may also create a degree of undesirable aerodynamic lift. It gets complicated. Without a wind tunnel and a gaggle of engineers its hard to predict what, if anything, will be different.