Air Dam and Front Undertray

[brelandt]

Originally Posted by red91sit

Not neccesarily, you go too low, and You increase frontal area causing more aerodynamic drag.

Not according to the March 2007 issue of Hot Rod Magazine.
Page 115 article "wind camp" under section, "tech theory" Sub article, "top 5 easy areo mods that almost always works" states this;

"You can usually get 90 percent there just by adding a dam striaght down from the front bumper......we have that big barn door on the front of the car, but keeping air out from under the car both reduces drag and neutralizes lift for solid areo gains....20 counts less drag and 50 less lift. the taller the car sits, the more important the air dam is."

It further states that the benfits of a large air dam outweights the higher frontal area.

Anyhow, Great info on you dam article!!!!!

Looking to do mine soon as well.

[zpiloto]

I agree with red91sit on this. I found it to be true with the mazda 626 anyway. YMMV.

[brelandt]

How tall are we talking about?

If you watch NASCAR which I don't or have ever seen a NASCAR you will see how freaking hugh their dams are as well to how low to the ground they are. The car has a much greater frontal area than any stock version of said car but is much more areo efficent.

Now if you are talking about adding a bumper to ground dam on lets say a 1985 K-Blazer with a 6 inch lift than yes there will be a neg. effect.

[Bill in Houston]

Originally Posted by brucepick

Bill in Houston,
I think you did a great job.

I drive an "89 Volvo with OEM air dam that was standard on those cars but I hope to add an extension downward based on what you showed.

Thanks!

I hope your extension works out well for you. Extending the OEM air dam should be a relatively simple task since your attachment points are all figured out.

Something that I read, and that I believe, is that behind the air dam, you need a smooth surface to get as much drag reduction as possible, so I built the undertray. The undertray also helps take a lot of flex out of the dam too.

Anyway, good luck and keep us posted.

[zpiloto]

Originally Posted by brelandt

How tall are we talking about?

Now if you are talking about adding a bumper to ground dam on lets say a 1985 K-Blazer with a 6 inch lift than yes there will be a neg. effect.

According to Hot Rod mag you quoted it would especially be need for the example above.

"You can usually get 90 percent there just by adding a dam striaght down from the front bumper......we have that big barn door on the front of the car, but keeping air out from under the car both reduces drag and neutralizes lift for solid areo gains....20 counts less drag and 50 less lift. the taller the car sits, the more important the air dam is."

Don't know about NASCAR but it didn't work for me but the belly pan sure did. YMMV

[brucepick]

Originally Posted by Bill in Houston

... Something that I read, and that I believe, is that behind the air dam, you need a smooth surface to get as much drag reduction as possible, so I built the undertray. The undertray also helps take a lot of flex out of the dam too...

Thanks Bill,

Hmm. The car has a short OEM belly pan but it starts just under the radiator/ac condenser. In other words, does not continue directly off the bottom rear of the air dam. Pan extends only about 18 inches to front of block. Pretty good considering it's from '89 though.

I could fairly easily put in a panel going across rear bottom of air dam to the front of belly pan. Should give some improvement, right? (When dam's lower extension is built I'd attach to rear bottom of that.)

Is that you have in mind? Of course a full lower pan would be best - but that's more involved; still considering that for when warmer weather gets here.

[Bill in Houston]

Originally Posted by brucepick

I could fairly easily put in a panel going across rear bottom of air dam to the front of belly pan. Should give some improvement, right? (When dam's lower extension is built I'd attach to rear bottom of that.)

Yep, that is what I was talking about. Sounds good to me. A small improvement, maybe, but an inprovement nonetheless.

[brucepick]

[Bill] - Yup.
They're all small improvements and they add up.

Heh-heh, back in the '70's the joke was that this guy said he bought every fuel-economy-improvement doodad and magic fluid he could find. Every one of them claimed to reduce gas consumption by 5 or 10 percent. Eventually he noticed that the tank got more and more full as he drove down the highway....

[Bill in Houston]

:-)

[brelandt]

Originally Posted by zpiloto

According to Hot Rod mag you quoted it would especially be need for the example above.

"You can usually get 90 percent there just by adding a dam striaght down from the front bumper......we have that big barn door on the front of the car, but keeping air out from under the car both reduces drag and neutralizes lift for solid areo gains....20 counts less drag and 50 less lift. the taller the car sits, the more important the air dam is."

Don't know about NASCAR but it didn't work for me but the belly pan sure did. YMMV

Belly pan would be the best way of going about it. Unfortunately for me and my pug nosed Sidekick with really low underhangs it's impossible.

The only way for me to keep the air from getting all turbulant and messy is to just block it off from getting there to begin with.

However, I have not done this yet and I may have to lower the truck first. When I do build mine I will make it just low enough to cover all of the hanging parts without lowering the truck.

If this doesn't work, than I will build the dam lower to the ground. Then if need be I will lower the whole truck, but as a last resort.

Also the dam works better if placed even with the front edge of the bumper and not behind it like almost all air dams are.

Anyhow, Good job Bill in Houston!!!!!