http://www.edmunds.com/insideline/do...ticleId=124466

sample quote:

"The deeper front airdam helps reduce the Tahoe's aerodynamic drag coefficient from 0.39 Cd to 0.34 Cd, but it also compromises its approach angle."

This is the first time in print I have read engineers officially say that a deeper air dam would help improve aero and Highway MPG but is not used because the bottom of the air dam would be damaged when the truck approaches rocks, curbs, parking lot concrete markers, etc.

In previous posts I have tested removing the 2nd Gen Ram front bumper air dam
and found worse MPG at a highway speed of 70 mph.

It is relatively easy to extend the air dam down about 2 inches
by using black plastic 'garden edging' and 3M 'Super Strong'
automotive trim double sided tape.

The garden edging is so cheap that if you later damage it on curbs or parking lot
concrete stops it costs little to make a repair.

Another option would be to use one of those 'brush bristle' mud flat/flying stone protectors like some trailer hauling pickups have fitted to the rear bumber...but use it at the front.

 

interesting... I also though that a lower dam would improve mileage... I'd also like to try an underbody panel along the outsides of the ram rails. figured out how to do it where it wont cost an arme & a leg...just the leg hehehe hahaha...

 

At least they have the good sense not to use it. The ones on our trucks only hang down about 2 inches as it is, and I ended up taking it off after most of it broke free of the bolts. It was always scraping off of stuff that the bottom of my bumber never scrapes off of without it.I never had any drop in mpg over it, but there's enough other factors in gas mileage that could have compensated for the missing air dam.

It's an intersesting read (I'm never really sure where you find all this stuff), but I think people need to get away from the idea that trucks and SUVs should get car like gas mileage. I mean as soon as you lift the truck 3" the 2" air dam just got cancelled out.

Also I esepcially like this part
"air dam would be damaged when the truck approaches curbs, parking lot concrete markers, etc"

I guess they assume 90% of americans can't drive or something. There's plenty of cars that you could actually wreck the front bumper off of curbs and parking lot markers. Just learn how to drive and don't hit them Offroad is one thing, but you shouldn't be driving around if you're wrecking into parking spaces.

 

So 5 one hundredths of 1 percent? I would like to see what happens if they lower the front by 2 inches and the back by 3-4 inches, then put on the air dam.

What would happen if you cleaned up the bottom with a sheet of aluminum or something?

 

an archived post
from a Ram owner who claims to have done some under pan simulations:

===
Im a 3rd gen'r but figured i would throw a little something in the mix here.
When i was in college a few years back we took a scale model of a
1999 Dodge Ram and did some wind tunnel testing on it
our results were as follows. (wind speeds at 70 knts)

Aerodynamic drag changes were:
.43 base

.51 with windows down and tailgate open
.49 windows down tailgate up
.43 windows up tailgate up
.37 windows up tailgate up tonneau on.
.32 windows up tailgate up tonneau on, and underbody sheeting in place.

The "underbody sheeting" was basicly like advertised on the new lexus. Only we didnt dimple it like a golf ball strictly out of lack of desire. But we found it interesting that if you were to do a large "skid plate system" under the vehicle how much drag you cut down. to go from .51 worst to .32 is a 37% increase in aerodynamic efficiency which should account for a 18.5% increase in fuel economy.

Another thing is that based on drag to run the AC compressor you would get better mileage with the windows up tailgate up and AC on than with the windows down in the same configuration.

I am currently working on a lightweight aluminum underbody sheeting unit for my truck to see if i notice any increase on a couple of 1200 mile trips i have coming up. Should be interesting.

Barrett_Fodder
Location: Rapid City, SD