Ford Focus Forum banner

1 - 20 of 26 Posts

·
Tarderatoraka: Red-SE-00'
Joined
·
7,592 Posts
Discussion Starter · #1 ·
I am going to try my hand at designing an underbody diffuser for my sedan.

Has anyone ever worked with these things?

...and...is it proper to extend it past the bumper a lil bit or does it not matter.

Thanks
Gabe
 

·
Registered
Joined
·
190 Posts
That is a sweet idea,you mean like on the lemans vette or a gt3000 car right?I would like to see it on an SVT bumper, it has a nice nest built in for it, just take the black plastic out. Anyhow i have a zx3 and will be making one out of fiberglass (just got started) or super thin aluminum sheeting.

VME

Please keep us posted....
 

·
Tarderatoraka: Red-SE-00'
Joined
·
7,592 Posts
Discussion Starter · #3 ·
Actually the initial design will be made of wood..then once I am satisfied with it I will take it to a metal shop and have them copy the design onto thin aluminum!

I would love to be able to try this on an SVT..due to the place where the mesh goes...but I think it will look good none the less.

Gabe...
yes...I will keep you posted!!
hehe
 

·
Registered
Joined
·
6,553 Posts
I always thought about making one but just a skid plate that went from the crossmember to the bottom of the bumper so it wasn't too obvious but it still stopped the air from getting trapped inside the rear bumper.
 

·
Tarderatoraka: Red-SE-00'
Joined
·
7,592 Posts
Discussion Starter · #5 ·
I am gonna run it from the back of the rear wheels across the gas tank and out the back.

it helps to flatten out the bottom of the car.
 

·
Driver > Car
Joined
·
23,988 Posts
i'm happy i'm not the only one concerned with the rear bumper being a parasail... i've been thinking about this for months!
 

·
Registered
Joined
·
1,918 Posts
i'm happy i'm not the only one concerned with the rear bumper being a parasail... i've been thinking about this for months!
Couldn't you just "vent" the rear bumper to let air pass through rather then get trapped? The R/S rear I have has "grills" to do so since its so much lower than the stock bumper. Or am I just being naive?
 

·
Tarderatoraka: Red-SE-00'
Joined
·
7,592 Posts
Discussion Starter · #10 ·
i'm happy i'm not the only one concerned with the rear bumper being a parasail... i've been thinking about this for months!
Couldn't you just "vent" the rear bumper to let air pass through rather then get trapped? The R/S rear I have has "grills" to do so since its so much lower than the stock bumper. Or am I just being naive?
Thats a very good idea!! But everybody has that damn STR speedhole thing drilled into their back bumper.

I want to be different...hey...its why I bought the car!!

and on the plus side...is that a diffuser slows down the air exiting from under the car...thus creating downforce.
 

·
Registered
Joined
·
556 Posts
It doesn't slow it down it speeds it up creating a vacume (low preasure) under the car sucking it down & better directing the air RED you have a PM
 

·
Tarderatoraka: Red-SE-00'
Joined
·
7,592 Posts
Discussion Starter · #12 ·
It doesn't slow it down it speeds it up creating a vacume (low preasure) under the car sucking it down & better directing the air RED you have a PM
Well from the research I have done so far its the opposite of what you are saying. As air enters a non-flat bottom car..ala any prod. car in america...the air pressure underneath reduces and moves faster, thus creating lift.

Now..in a non flat bottom car the fins in the diffuser slow that air back down and raise the pressure thus creating downforce.



Please refer to this link.

GAbe
 

·
Registered
Joined
·
556 Posts
Ok but it's my understanding in aerodynamics that say with a wing to CREATE lift you want a low preasure on top of the wing & a high preasure on the bottom...to creat downforce would be to switch this... with Lemans cars they speed up the air coming out the bottom & out the back in order to suck the car down-more air traveling over the top than underneath...yes no? Someone with a degree in this stuff please chime in here
 

·
Tarderatoraka: Red-SE-00'
Joined
·
7,592 Posts
Discussion Starter · #15 ·
I am not gonna start on this until after Sept 27th.

Its the last show of the year in Houston...so a bunch of stuff goes under the knife for 04!!

 

·
Registered
Joined
·
62 Posts
It doesn't slow it down it speeds it up creating a vacume (low preasure) under the car sucking it down & better directing the air RED you have a PM
Basically the right idea. This comes from Bernoulli's Principle. Basically he found the air to work the same way as a liquid. And found that higher velocity leads to lower pressure. Anyways... if you wanna see that this works, take some bubbles. Blow one and then wave your hand above the top of the bubble. The higher velocity air should create lower pressure and inturn cause the bubble to raise or float. So for downforce on a car you would want to create a pocket of lower pressure air underneath the car, by increasing the velocity of the air traveling underneath it.
 

·
Tarderatoraka: Red-SE-00'
Joined
·
7,592 Posts
Discussion Starter · #17 ·
But with the air getting trapped underneath a car THAT IS NOT FLAT ON THE BOTTOM...is creating lift.

As the car moves faster more air gets trapped under their..essentially sucking the car off the ground.

Now..with a flat bottom..its all flying right past the car and not getting stock...and then the channel at the end helps to direct and slow it down to create downforce.

This is what I understand.

Gabe
 

·
Registered
Joined
·
62 Posts
But with the air getting trapped underneath a car THAT IS NOT FLAT ON THE BOTTOM...is creating lift.

As the car moves faster more air gets trapped under their..essentially sucking the car off the ground.

Now..with a flat bottom..its all flying right past the car and not getting stock...and then the channel at the end helps to direct and slow it down to create downforce.

This is what I understand.

Gabe
The object of a diffuser is not to slow down the air underneath the car. From the site you posted, it explains it as helping the faster moving air from under the car meet the normal speed air behind the car. Basically it allows the air to keep a high velocity under the car without a pocket of slow moving air forming underneath the car. Remember that higher velocity creates lower pressure.
 

·
Tarderatoraka: Red-SE-00'
Joined
·
7,592 Posts
Discussion Starter · #19 ·
ok ok...i had to re-read it a few times now!!

haha...I get whats going on!!

and BTW...I got a C in physics...so uhhhhhhhhhhhhhhh yeah!!
 
1 - 20 of 26 Posts
Top