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Old 02-09-2014, 12:57 AM   #1
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That air dam thingy?

Under the front of the Jeep, that air dam? Plastic shield looking thing.... What is that? is it for aerodynamics? Protection? Do I need it? I removed it to install my grill gaurd and light mounts bc I had to take the bumper off to do those things but I put it back and now I'm wondering. Thoughts?

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Old 02-09-2014, 12:58 AM   #2
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Leave it off. It would get ripped off on the trail anyway.

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Old 02-09-2014, 12:59 AM   #3
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Shaved mine down to fit behind my bumper. I think they are just for looks when being sold from the factory so you don't see the frame. Shouldn't be a big deal without it.
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Old 02-09-2014, 01:00 AM   #4
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Leave it off. It would get ripped off on the trail anyway.
Yep, garbage.
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Old 02-09-2014, 04:06 AM   #5
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It reduces drag by diverting the air away from the undercarriage and it reduces hood flutter. You can replace it with a skid plate.
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Old 02-09-2014, 04:20 AM   #6
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If you're one of these jeepers that frequently use the highway and concerned with MPGs keep it, trim it if needed. If it falls off or rips, oh well.
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Old 02-09-2014, 04:50 AM   #7
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If you're one of these jeepers that frequently use the highway and concerned with MPGs keep it, trim it if needed. If it falls off or rips, oh well.
Well said! Just keep your window open in case you have to jump out and lay on the hood when it start fluttering violently. Actually just get some stiffer hood latches. And if you tow in the heat you may want to back to where it fell off and put it back on temporarily since it can reduce radiator efficiency.
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Old 02-09-2014, 06:18 AM   #8
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It was the second thing that got pulled off our JK's. Right after the motor cover.
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Old 02-09-2014, 06:34 AM   #9
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Old 02-09-2014, 12:53 PM   #10
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try backing up in mud or water and see how long it stays on!
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Old 02-09-2014, 12:56 PM   #11
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Jeep would've gladly omitted it for extra profit if it didn't serve a purpose.
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Old 02-09-2014, 02:22 PM   #12
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It does affect fuel economy and cooling on the highway..
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Old 02-09-2014, 03:04 PM   #13
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Jeep would've gladly omitted it for extra profit if it didn't serve a purpose.
I wouldnt be surprised if it were some sort of EPA requirement
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Old 02-09-2014, 07:25 PM   #14
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It is there to produce lower air pressure under the vehicle, which helps pull air through the radiator and engine area while driving. The reason some people say the hood vibrates is because of the excessive pressure in the engine bay...that is a sign that air is not moving through as it should be. Proceed with caution.
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Old 02-09-2014, 08:07 PM   #15
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Its for aero.
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Old 02-09-2014, 08:12 PM   #16
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try backing up in mud or water and see how long it stays on!
Ahhhhh, that brings back fond memories of when I tore my buddies off pulling him backwards out of a mud hole. I laughed my off the rest of the day.
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Old 02-09-2014, 08:13 PM   #17
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The reason some people say the hood vibrates is because of the excessive pressure in the engine bay...that is a sign that air is not moving through as it should be. Proceed with caution.
Can you please expand upon this claim. It really doesn't make sense.
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Old 02-09-2014, 09:45 PM   #18
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If the air dam is in place, it creates a low pressure area behind it at, say, highway speed. Because air, or any fluid, flows from a high pressure to a low pressure area (path of least resistance), the air dam helps draw the high pressure air through the front of your vehicle, where the radiator and engine are. The air in front of the vehicle is a higher pressure because the vehicle creates a "bow wave" in front of it as it passes through the air. It's very easy to see in a wind tunnel, if you happen to have one!
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Old 02-09-2014, 09:57 PM   #19
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I've been running an aftermarket bumper for years. The only time I get hood flutter on the highway was in a crosswind of 15 mph or higher.
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Old 02-10-2014, 06:14 AM   #20
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Maybe our new member would like to take a stab at what that plastic engine cover is there for other than to trap dirt and make cleaning it up a pain.
air dam and engine cover long gone on mine.
Hood flutter could have to due with sheet metal is so thin like paper.
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Old 02-10-2014, 06:18 AM   #21
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Maybe our new member would like to take a stab at what that plastic engine cover is there for other than to trap dirt and make cleaning it up a pain.
air dam and engine cover long gone on mine.
Hood flutter could have to due with sheet metal is so thin like paper.

To make it pretty? Bahaha

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Old 02-10-2014, 08:30 AM   #22
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To make it pretty? Bahaha

Also quiets valvetrain/injector noise
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Old 02-10-2014, 08:58 AM   #23
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If the air dam is in place, it creates a low pressure area behind it at, say, highway speed. Because air, or any fluid, flows from a high pressure to a low pressure area (path of least resistance), the air dam helps draw the high pressure air through the front of your vehicle, where the radiator and engine are. The air in front of the vehicle is a higher pressure because the vehicle creates a "bow wave" in front of it as it passes through the air. It's very easy to see in a wind tunnel, if you happen to have one!
Thanks for the response. I understand fluid dynamics relating to what you're explaining. What I didn't understand was your claim that excessive pressure in the engine bay causes good flutter and that in turn meant air wasn't flowing appropriately and caution should be taken. But I was really interested in how you think excessive pressure is building up and how that causes flutter. As you said the flow of air goes from high to low pressure which should also create a pull on the engine hood causing it to tighten down opposing flutter.
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Old 02-12-2014, 10:17 AM   #24
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So would an aftermarket skid plate correct the hood flutter and improve the mileage back ??
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Old 02-12-2014, 11:18 AM   #25
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try backing up in mud or water and see how long it stays on!
That's how I lost mine, first self-made mod, inexpensive and doesn't much effort, lol
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Old 02-12-2014, 03:35 PM   #26
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So would an aftermarket skid plate correct the hood flutter and improve the mileage back ??
If hood flutter worries you, get a set of Drake or Rugged Ridge hood hold downs for around $100-$120, and then get rid of the air dam. Expensive skid plates probably won't help.
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Old 02-12-2014, 03:45 PM   #27
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Take your hood spring off and see if that solves the hood flutter. It did for me and many others and I live in windy Kansas.

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