It is too early too tell for sure exactly the results of my experiment are so far, but I have an idea where I am headed. I drove 100 miles last night, mostly highway. About half the trip was 70 mph with some construction slowing us down to 60 mph for limited amounts of time. The second half is secondary highway 45-55 mph. This is the same route I took two years ago to get to work when I first started my spoiler experiments.
I am defiantly getting down-force, and lots of it. When I drove in the rain a few nights ago at around 50 mph I did not fear for my life and want to pull over to lock the hubs into 4WD as is typically the case. This was my first clue.
Last night I'd guess the down-force increase was close to 200 lbs at 70 mph, and 100 lbs at 50 mph. This is about half-way in between the force I remember experiencing when I installed a really tall rear spoiler with support spars (see Photobucket album picture -
http://i184.photobucket.com/albums/x...20Up/GUR-4.jpg).
I'd like to take the truck up to 85 mph for a short blast after obtaining my fuel mileage estimates. I bet the down-force would be massive, as it increases a lot with speed.
Right now I 'm pretty sure that I'm consuming more gas than normal. However it could save me gas this winter if it extends 2WD use and has me locking it into 4WD less often. Kind of a draw really, just a thought at this point.
Here is a diagram with my thoughts of what is occurring.
S10 4x4 Pick Up pictures by kach22i - Photobucket
The diagram is not totally arbitrary or "made up". I did notice more deflection and rippling in the tonneau cover (in the last two support spar areas) as I looked in my rear view mirror, a speed spike at 75 mph while passing made things even more obvious.
My wife said she could feel the difference too. She said the truck felt more planted. Even though the truck is an automatic it felt to me as if I needed to shift up a gear. This is kind of similar to the torque hold down force I get in my old Porsche 911 by keeping it revved up at 5,500 rpm in a turn or while driving in the rain. The lower gear with high rpm's just keeps the car planted, the truck was getting similar results aerodynamically and not through torque. I was also impervious to cross winds last night which was nice. No lane wandering, the truck tracked nicely.
What is the best way I can verify this flow diagram? I have no wind-tunnel, no smoke generator. I don't think wool tufts are going to tell me much, or will they?