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Air dam / Front Valance helps mpg?


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My 96 silverado doesn't have the air dam up front, you know the plastic thingy below the bumper. IMO, it looks fine without it, but If I were to get one, is there any real mpg difference? I figure its less wind resistance, and if its 3" inches tall, its like my truck has a 3" lift up front right now, and I'd be putting it back to stock height. Does anyone think its work the $80 bucks to order one? I check my mileage pretty religously and managed 19mpg on my last tank... if it would yield a noticeable difference I'd order one.

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I doubt you are going to get any better than you are getting right now. Im sure in a perfect world it would help. I would tell a friend how shitty it looks with it, help him take it off of his truck, and kinda casually bolt it up to yours. Or hit up a junk yard.

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IF it didn't do anything the manufacturer wouldn't have spent the money designing, testing having them made and then mounting it. The reason for the dam is to prevent too much air from traveling under the vehicle which causes uplift of the vehicle which results in lesser mpg and poorer handling. True trucks look much better without them.

I doubt there's anyone on here that could tell you how much mpg you'd gain if you were to install one. You may have to visit some technical forums for that....OR do the test on your own!

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Sometimes the removal of the airdam affects the cooling system. Aside from that I doubt that, at the speeds you are probably seeing, it will make any noticable difference in mpg.

I have noticed this personally. Removed the air dam because I replaced a bumper, did not have the little plastic hoo-rah's that hold it on (the old ones were toast) and it ran hotter afterwards, trans and coolant for the 3 days until I got the correct fasteners.

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I have noticed this personally. Removed the air dam because I replaced a bumper, did not have the little plastic hoo-rah's that hold it on (the old ones were toast) and it ran hotter afterwards, trans and coolant for the 3 days until I got the correct fasteners.

AIR D.A.M. (Directional Airflow Modulators) 👍

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I dont see them being very useful on trucks since they all have big gaping grills that let in a huge amount of air for the radiator. Most cars need them to scoop air up to the radiator cause of the small grills (or lack of) they have.

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I dont see them being very useful on trucks since they all have big gaping grills that let in a huge amount of air for the radiator. Most cars need them to scoop air up to the radiator cause of the small grills (or lack of) they have.

What has been explained to me, is that on a truck, it keeps the airflow coming under the bumper going down, instead of tumbling upwards and creating a vacuum/non-flow condition across the radiator.

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It's there for a reason, what ever it may be otherwise as I said before the manufacturer wouldn't have spent the time, money and effort of designing, testingm making and installing it if it doesn't give a positive result.

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  • 1 month later...

I've read on several MPG forums that they do make a difference to your mpg, small though it may be. The rule of thumb is to find the thing on the underside of your truck that hangs down the lowest and make your air dam that low as well, but no lower (diminishing returns). You can make them out of any old piece of fairly rigid plastic and just bolt it on with L-brackets. Do a google search, lots of people have done it.

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I will eat my hat if you gain one mpg. The thoery that the "engineers" are only making "usefull" improvments on the truck is bogus. Its for looks. Test it out if you can do it for free otherwise enjoy a truck with a tad less palstic. Looks better in my opinion.

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I will eat my hat if you gain one mpg. The thoery that the "engineers" are only making "usefull" improvments on the truck is bogus. Its for looks. Test it out if you can do it for free otherwise enjoy a truck with a tad less palstic. Looks better in my opinion.

Depends on the truck. My S10 looked like poo without an air dam, in my opinion.

On taller vehicles an air dam won't have as much of an effect as something where the airdam can be close to the ground. Guys on Ecomodder have proven pretty substantial gains in mileage with improved air dams. Keeping air from going under the vehicle helps reduce aerodynamic drag by keeping the amount of air traveling under the "dirty" (aerodynamically) underside of the vehicle. Why aren't cars engineered with these larger air dams? Hard to make them asthetically pleasing, and it's hard to sell a car that can't clear a speed bump without body damage, let alone survive winter roads.

On taller vehicles the aerodynamic advantages will be less dramatic in terms of drag savings, but there are still other benifits. An air dam creates a low pressure area behind it, which in turn lets more air be drawn through the grill/radiator. Sounds weird, but it works. Most air that flows through the radiator is expelled out the bottom of the engine compartment, so creating a lower pressure creates higher flow. Trying to funnel more air into the radiator isn't very effective, it's very hard to create much pressure increase at road speeds (even "ram air" is rarely good for much more than a few tenths of a single psi). However, an air dam can create a pressure drop close to a full psi behind it. Greater pressure differential means greater air flow.

With the original poster see a noticable mpg or temp change installing an air dam? Probably nothing he'd notice. But the engineers aren't just wasting time and money designing air dams, they serve purposes. You should see the amount of aerodynamic work VW did on my wife's Passat. There's all sorts of ducting, deflectors, belly pans, etc, and that's just on the bottom of the car.

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Here's a link to some aero stuff you can do to improve mpg. You'd get some seriously funny looks doing most of the things, but you'd also get some results.

http://ecomodder.com/forum/fuel-economy-mpg-modifications.php

I think the best, most cost effective mpg increase would come from your right foot. In other words, driving like a granny.

Hey dirtbeater, if you do try it, post the results because I'd be really interested in them for an actual truck, not just some micro-car.

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Well guys, I havent done the air dam, but I did change tires. I have a '96 1500 Chevy V8 4x4 ext cab. It had chrome 20s on it with sticky 11" tires. I juyst put the stock wheels back on with 245/75/16 tires, which are a little taller and narrower, and seems like I've gained 1.5 mpg. I just did a full tank of 60/40 hwy city, and got 17.1 mpg, I usually get 15.5 or so on a similar tank. So skinny tires certainly help.

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Well guys, I havent done the air dam, but I did change tires. I have a '96 1500 Chevy V8 4x4 ext cab. It had chrome 20s on it with sticky 11" tires. I juyst put the stock wheels back on with 245/75/16 tires, which are a little taller and narrower, and seems like I've gained 1.5 mpg. I just did a full tank of 60/40 hwy city, and got 17.1 mpg, I usually get 15.5 or so on a similar tank. So skinny tires certainly help.

Wide tires take a bite out of fuel mileage, more rotating mass (weight) to spin.

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  • 8 years later...

Having worked in body engineering at one of the big 3 for 30 years, I can tell you they spend a LOT of time figuring out aero improvements - enough to build their own wind tunnel to do it (millions of $). A front air dam will definitely affect mileage and engine compartment airflow resulting in cooling performance.  Even on sports cars, the aero engineers have a lot of influence on the resulting look, in cooperation with styling folks. Adjustable suspensions that lower the vehicle at speed is all for mileage - they wouldn't do it if it didn't work - that stuff ain't cheap. Less frontal area and better Cd. Fat tires are more rotating mass as mentioned, but at speed, it is frontal area they affect. Frontal area is a big enemy, just like Cd. Front air dams would likely be bigger except for curb clearance (and other related obstacles). Most vehicles now, including trucks, already have or will soon have full underbody skirts to smooth airflow. The upperbody has had so much attention and improvement, it is now the underbody that needs attention for further aero improvements.

As for DIY, on my previous 2003 van, I took a mostly bald automotive size tire, sliced it radially and cut off most of the sidewall except enough to leave a lip to bolt it to the bumper. I left a little lip for the bottom as well to simulate the wing tips as mentioned earlier and you see on Formula cars and other racers. Be aware the inside of the tire faces forward for the lip to work.  I drove several trips prior to this addition, with mileage that inspired the change. I am confident I got about 1.5 mpg improvement, and a better feel on the road - less floating around in winds. The front end felt "settled." I cannot verify that on my newer 2013 as I did not wait to see what mileage I got - put one on right away.

Of course, most folks know the easiest improvement is tire pressure - I've seen the charts and it is significant.

Thanks for "listening."

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I lost the air dam on our Chev conversion van and it became "floaty" on the freeway at higher speeds. Made a very noticeable difference. Just like race cars the dam is intended to keep air from going under the vehicle and creating lift which kills speed and mpg. Don't want turbulence under there.

Edited by Piney Woods
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