How much does a belly pan or front air dam decrease drag?

[freebeard]

The wind will rip it off at the first opportunity.

High speed air is as unforgiving as a curb. Observe the struts and turnbuckles on a time attack car just to get a little adjustment.

A backward leaning air dam will increase underbody air pressure. A forward leaning air dam will decrease underbody air pressure. The extreme is the diverter on the bottom of the air dam on those time attack cars.

If the concern is ground strikes, why not a passive, hinged air dam with a roller on the bottom?


http://www.carscoops.com/2016/01/its-been-70-years-since-first-vw-beetle.html

Like this on a Cal Looker instead of the KdF-Wagen.

[teoman]

If you have an airdam that is big then yes the wind would rip it apart. But something that is not so huge should be able to stay onboard.

Passive with rollers is a good idea but would the wind not push it back? How about passive with springs, the wind would push it open.

Is it even worth doing anything to this car?

https://goo.gl/images/DfCjbY

It seems fairly optimised already down there.

At 1:30 you get a view of the underside.
http://youtu.be/nTwkBXN6gtA

[ecocruze]

I have been looking at doing something for my explorer. From what I have seen SUVS tend to get a larger boost. That would be why most new ones are sporting factory air dams. Yet it's interesting when u look at the rear of many they still leave pockets that will catch a ton of air in the bumper. Little parachute action in the 2000s will have to check a bit closer on some of the newer models. Wife's 2016 expedition has some parachute going on but nothing drastic like the 02 ex. I feel with most cars they have a slight rake to them now and nothing significant hanging down. Golf ball dimple laminar floor deal would be probably the best way to go for a belly pan obviously. Lot of work though from what others have posted. Otherwise wheel spats seem to be a great one. Since adding a dam decreases your ground clearance. You may have to suck it up and spend time on the pan if u drive in rougher areas. My local area would be terrible for a dam on any car. Transition into parking lots for the most part is only suits for an SUV. My Monte Carlo bottomed out like crazy as does my cruze that replaced it.

[gumby79]

I had 10" under my air dam corners and 12" in the canter covering all the junk hanging down under the nose. 30" forward of the contact point of the tire. It would still hit the "bad" driveways, cleared sidewalks and parking blocks (tryed 8"and 9" both hit too small of an aproch angle)

This was just before Darco.
Results from Darco
+.02Cd .(more drag)

"I have not seen an air dam that had a positive result."
Layne Christensen
Darko Technologies

And this is the man who runs the Ogden wind tunnel were many Bonneville salt flat racers test.
Conclusion
The air dam is a pice of a package. Without the belly pan it has trouble beeing positive.

[ecocruze]

Not sure how to take that but it's strictly dependent on the vehicle and the application of the mod. I understand the point of all piece of a package but people have been posting positive results with theirs on here. Don't see how that can all be summed up to driving more attentive. Need to have someone's aba testing linked in here.

[COcyclist]

Like this? http://ecomodder.com/forum/showthrea...9-a-27167.html

Or. http://ecomodder.com/forum/showthrea...-b-9732-3.html

[ecocruze]

Thank you!!!

[ecocruze]

Don't forget the 98' Odessy 15% increase in highway economy.

[JockoT]

[chefdave]

Hi have not done aba testing on my air dam but stablitiy in cross winds is remarkably improved. Have not noticed a drop in mpg maybe a slight gain. Bottom of car is quite flat from factory. Think i will gain more by reducing parachute effect on rear bumper. Averaging 40 imperimal mpg on a 2.0 auto pugeot 406 estate. Car weighs about 1800kg. Full 70 litre tank might increase it abit. Gearing is almost diesel like. Top gear pulling 2100 revs at 60mph. Very high for a heavy 2.0 auto. Pugeout factory figures are nax 37mpg at 55mph. So must of gained something.