I did a trail with numerous stream crossings, all 12-18" deep. No water issues in the engine bay, but the crossings were very short (10-15 feet wide). I think it's been proven that for sustained deep water fording and mud that it is better to remove the air dam, usually it's these circumstances that it gets removed anyways

 

Here is what I said back in June when this same issue came up.

I can't believe that anybody would remove this critical piece to the areodynamic flow designed into the JK. Why, without it, the stability of my JK would be gone at over 180 mph.

The air dam also is an essensial piece of armor to protect the underside from obstacles such as squirrels and woodpeckers.

If you don't have an air dam and you run over a woodpecker, its last dying act may be to peck holes into your oil filter. You'll wish you had kept yours on when you're caught out in the middle of nowhere with an oil filter full of pecker holes.__________________

 

Taking it off is easy.

Gas millage has not changed for me.

 

It's not significantly cosmetic, so it must have other purposes.
You don't invest money in tooling and pay union wages to install something unless it adds real benefit.

 

my airdam removed itself(came off in 1st attempt at deep water crossing,had to chase it down stream and retrieve it)as for woodpecker threat thinking of starting thread on chicken wire/oil filter armour mod to protect from evil woodpecker threat

 

Lol, tell that to our product management team ...

 

Anything that ugly has too affect millage or else it wouldnt be there. i have noticed a difference too. unfortunally mines lost in the sand dunes somwhere it doesnt take much to rip off at all i wouldnt mind making somthing like it in plate steel

 

I noticed a negative change in mpg but I think removing that stupid thing was still worth it.
No affect to hood lift problem

 

In the interest of science and $4 gas, I decided an experiment was in order.

I removed my air dam when I stubbified. I didn't reset the MPG computer at the time and didn't have any road trips to check its effect. The road trip since removal included adding BFG KM tires, adding KC daylighters, and shortening the stubs, so I couldn't pinpoint what sapped my MPG.

Well, on an out-and-back pass of 10 miles on a relatively flat country road, the air dam improved indicated MPG by 2.

AC stole about .5 MPG.

The big shocker (and must be due to some aerodynamic flow quirk around the mirror and/or windshield) was gaining over .5 MPG by opening only the driver's window. I had decided to call it quits and come in, so I opened the window and the indicated average started climbing, which piqued my interest and led to another test. Conventional wisdom for modern vehicles is to close the windows and use AC, but our Jeeps are brickmobiles, so the aerodynamic effect is thrown out the window. I know that having all the doors off drops the MPG like a rock, so having the driver's window open is a strange one.

The air dam is about as wide as my original stub cut length. It now sticks out past the end of the bumper and looks almost as wrong as 18+ inch wheels. I'm planning a long-term study of its MPG effects and may also narrow it to match the current stub length.


Oh, and I've only noticed an effect on hood flapping by changing the rake. With kiddie and tongue weight on the rear, the hood flaps like mad. Factory rake leads to very little flapping.