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Old 08-07-2011, 07:23 PM
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the value of air dams/ spoiler

Mentioned my air dam I made out of plastic lawn divider. Drove to Portland sat. holding at 65mph with slite head wind Filled up and got---19.88 mpg . This is a l least a 1 mpg inprovement. The car --1957ranch wagon / 351w 4v/ Aod trans / w..4:11 gears 650 holley This mod is simple and does not show oh my car . Give it a try

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Old 08-08-2011, 09:34 AM
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Got any pics, this is interesting. Does the air deflect to the engine bay, what was the purpose? Many air dams help cool the car. Dan
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Old 08-08-2011, 09:41 AM
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no photos

Sorry can't do pictures . Ive have also used rubber convayer[sic] belting ,much stifer.Brackets can be used from lumber framing. It worked for me
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Old 08-09-2011, 01:49 AM
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Most don`t understand what air dams are for and don`t care of they get broken, removed, what have you. Far as I know there purpose is when the vehicle is at any speed, the incoming air hits the dam which is like air hitting a wall, it`s got to go over or under the wall. In the air dams case on a vehicle it does both. Some is deflected under the vehicle, the rest is deflected into the condensor and radiator to greatly aide cooling. It also packs the engine compartment with air to keep the engine bay cooler as well.
On older vehicles that didn`t come with air dams, you can experiment around with width, height, lenth, placement until you find a spot where it directs air to flow smoothly under the vehicle reducing air drag and thus helping fuel economy. For those that have lost, broken or removed air dams don`t bother to replace them and the result is they spend hundreds of dollars replacing perfectly good parts and it still runs hot and they can`t figure out why. It don`t occur to them that a simple air dam not being there is causing the problem. On vehicles with little to no front grilles the air dam is very important, as on these types of vehicles if the air dam isn`t there the car will run hot regardless of what season it is.
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Old 08-09-2011, 06:06 AM
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Many current cars have very little airflow through the grill, and use an air dam to redirect cooling air up to the radiator. Quite a few cars also used to use an air dam to reduce the amount of air flowing under the car, since it helps make the car more "slippery" (flow under the car is never smooth). The wrong airflow under the bumper can also affect the amount of lift on the front end, which affects high speed handling.

Bruce
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Old 08-09-2011, 08:00 AM
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Quote:
Originally Posted by 75gmck25
Quite a few cars also used to use an air dam to reduce the amount of air flowing under the car, since it helps make the car more "slippery" (flow under the car is never smooth). The wrong airflow under the bumper can also affect the amount of lift on the front end, which affects high speed handling.

Bruce
I think it was in 78 that the full Size GM pickups started using them.
And where I grew up, they did not last long under the front of the truck.

But, I think this little piece of plastic that was directing air around the truck instead of under it, was part of the reason I got 21mpg in my 305 powered longbed 1/2 ton. Not kidding either, once drove from Idaho Falls Idaho to Los Angeles----never stopped for fuel.

Years later---much bigger engine and lowering 3" (air dam still there)
I can get 14mpg with a 454 as long as the secondaries don't start feathering.
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Old 08-09-2011, 09:55 AM
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I'm currently working on air dams for my Willys. Ugly as they are.
So far my 1 1/2 'chin scoop' which helps direct air up into the radiator from below the grill has solved the cross wind temp increase and the following wind temp increase. My temps are now pretty stable throughout speeds from idle up to highway speed.

Next are the dams from the grill to the edge of the fenders. These need the be either flexible or hinged to survive road trash. A good example ..last night we were cruising along and the car in front swerved to miss about a 4 in piece of tree limb on the road. He missed it but it spun around right in front of me. I had no chance to avoid it and ...bam the right front wheel hit it dead center. It hit at least twice more under the car then the Vette behind me collected it with his air dam. His dam nicely just folded back and we pulled it back in to position ... no damage.

So these need some flexibility or they simply need to be able to be ripped off on contact to be replaced when you get home. My chin scoop is mounted with 10-24 plastic screws so it can be ripped off without damaging anything....I hope. the log just missed it last night.

We studied automotive aerodynamics in part of the fluid dynamics class in college. NASCAR guys spend a lot of time making theirs work within the rules. So you can take free lessons from them. From college the closer to the road you can make them the better. Front dams cause a pressure reduction under the car which the expanding hot air from the front motor fills thus helping flow through the motor area. It's very complex believe me. Side dams as seen lately on the big semi trucks also help clean up the flow under the trailer..or in our case the underside of the car. All of today's car use some type of aerodynamics to improve mpg. Much of it is compromised by the need for road clearance however. Being hot rodders we can live with less compromise if we don't mind fixing broken stuff occasionally.

If you look at travel trailers you will see plastic belly pans on nearly all of the large units....same reason.
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Old 08-09-2011, 10:58 AM
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I have a little air dam on my 86 Cutlass. I've also got an aluminum radiator. The car will run at about 160 degrees on the highway which is pretty good imo. I would like to experiment around with a bigger one though. Maybe something lower to the ground.
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