fcunderwater

How much does using a rear diffuser help? Would it be a good buy or just something for serious race setups? thanks for the help

RETed

Majority of them don't do anything.
Most of the time, they are for looks.


-Ted

fcunderwater

alright thanks

AcidAngel7477

iTrader: (16)

not true, most of the diffusers, if its a good one and not a crap knock off, they only help in the case of someone drafting you. the diffusers allows them to not be able to draft you therefore no catapult effect..


:AA:

Evil Aviator

Silly me, I thought a diffuser was a device that reduces air velocity and increases static pressure, and aids in transitioning airflow from one source to another. I think we should all get a diffuser to keep the army from drafting us and getting catapulted into a war or something.

ENZO182007

lmao
that was awsomely evil
dang draft dodgers

Black91n/a

To be most effective you need to have a flat underfloor, and a very low ride height. They're not legal in most racing classes so they're not used much.

Saten

Good luck with the stock underbody....

yusoslo

And yet I thought that a diffuser was used to reduce underbody turblance and SPEED up air flow underneath the cars chassis, which then in turn will create a lower pressure ratio in relationship to the pressure on the top side of the car. A diffuser would aid nothing in downforce, but by reducing under chassis turbulance it increases the ratio of the two opposing forces on the car.

but what do I know.

FYI you can install oil squirters and smoke screens easily in them too to distract people tailgating you.

fcunderwater

hmm okay so if I get everything that everyone is saying it's more of a high performance add on. Alright thanks guys

Evil Aviator

I'm beginning to think that is because only you and I know what they are supposed to do, lol.

melicha8

iTrader: (1)

So it'll work only if it's expensive, got it thanks.

staticguitar313

iTrader: (2)

Pretty much what evilaviator and yusoslo said, it'll speed up air under the car, sucking it to the ground

(think of an upside down airplane wing but not really)

but on a stock FC um its no going to help much, the car sits too high and its not smooth enough underneath. Doesn't change the fact that i'm still going to buy one though, and i'm going to lower my car and attempt to smooth out the undercarriage with plating or something.

If anything it looks ******* sick . . .

stevensimon

iTrader: (11)

they totally rock till you go over a speed bump or through a gutter and it breaks and you cry... if your exhaust now ever scrapes then the diffuser will be destroyed..

staticguitar313

iTrader: (2)

you trim the diffuser to fit around the exhaust and from what i've heard only light trimming is needed around the APexi' and Corksport models, something like the Greddy duals would make the diffuser near worthless

DarkKnightFC

They allow someone to not draft you???? Are you serious? Simple explanation, Take a piece of paper, a couple inches wide by maybe 8 inches long. Hold it on one end. Put it up to your mouth and blow across the top of it. It lifts the entire piece up. NOW imagin the curve that the piece of paper made, upside down. Air flowing over it would suck it down correct? HOLY ****, that means the curve in a diffuser creates downforce when air flows over it? I guess so.

DarkKnightFC

I'm pretty sure I'm less intelligent having read all the explanations in this thread.

Evil Aviator

I didn't say that. I said that diffusers SLOW the air down. However, I must be wrong because everybody else thinks differently. Then again, I could be right. Only I know the truth, hehehe.

More like "not really".

That's wrong too, lol. I think a simple dictionary definition would steer you in the right direction. All diffusers do the basically the same thing, regardless of whether they are mounted at the rear of a car, inside a turbocharger, or at the end of a hair drier.

Easy answer: Yes, it is more of a high performance add-on (assuming it even works, lol).

insenothepunk

Well really it doesn't "speed" up the air to create down force. Speeding up the air would create more up force. Take the airplane wing example. The air flowing over the wing goes slower than the air flowing under the wing. There for creating a "vaccum" above the wing wich creates lift. To create more down force under the car you would have to slow the air under the car down. Making the speed of the air on top of the car closer to the speed of the air under the car. Meaning less up force. But hey I've only been flying airplane's since I couldn't see over the dash and had to fly by instrament only. So eh what do I know.

staticguitar313

iTrader: (2)

oh well, i was mis-informed, not exactly a new thing, thanks for clearing that up. Still buying one :P

Evil Aviator

They do look kinda cool.

jgrewe

iTrader: (1)

From the looks of the pictures the car would have to be about 6" lower for that thing to do anything but add weight.(if it was designed properly in the first place)

I alway thought a diffuser made a small amount of air entering the front expand into a larger volume area as it traveled toward the rear, therefore creating downforce. Gee, have I been mistaken all these years?

staticguitar313

iTrader: (2)

Cha i think it'll look great with a corksport single, its not like i'm putting this on an N/A either . . . ^_^ waiting until i pick up my TII (hopefully tomorrow)

Juiceh

iTrader: (4)

Wow, there is so much missinformation in this thread it is sad.


OK, an AIRFOIL(plane wing) is flat(ish) on the bottom and curved on the top. The air flowing over the top goes FASTER than the air under the wing to meet up with the air flowing underneath at the same time at the end of the wing. This effect creates a low pressure zone above the wing and high pressure below this is known as the Bernoulli principle. This creates "LIFT".

I diffuser does the same thing except it is upside down. Air flowing over the car by design moves faster than the air underneath. There is no real way around that. This is why cars can get airborne at high speeds and lift off the ground. Because they have actually reached the point where the lift being created by this effect is greater than the weight of the car and the forces keeping it on the ground. This is why F1 cars have wings on the Rear AND front which are upside down airfoils, at speed they create "lift" but the lift is pressing down keeping the car on the road.

Take a look at this diffuser:

This is a Sanai Works FD diffuser. Notice the "exit" of the diffuser is wider than the "inlet". As the air enters the inlet side of the diffuser it is accelerated thru the exit due to the widening shape, think of that section of the diffuser that gets wider as having the same effect the top side of an airfoil has. The air must travel faster to exit that area to reach the rear of the car the same time the air flowing over the car does. Think of it like the combination of that V shape and the road literally pulling more air thru the underside of the car. Remmember the air going under the car reaches the end of the car the same time the as the air going over it but the air going over it has to travel faster? Well the diifuser helps to counter SOME of that effect by speeding up some of the air flowing under the car and creating a suction\negative lift effect.

Here is another picture that will help.


Here is a RE-Amemiya Shine Auto Replica, which by the way will work just as well as an original...

Now pretend for a minute that the wooden floor was the road and your diffuser was at this height. Look at the smaller size of the inlet of the diffuser vs the exit. Notice how the end of the diffuser curves upwards? This shape in relation to the ground helps to accelerate the airflow and creates the suction\negative lift effect due to the low pressure zone created by the acceleration of the air.

so-mars

(not a scientific attempt as i have no clue and can't even change my oil but seems fairly logical)

well diffusion as someone mentioned is what a hair dryer attachment will do, space out the air molecules wider

with the crunk i would think most 15 year old cars w/o racing underbodies would have on them, it would stand to reason that there is a fair amount of diffusion already albeit not controlled

there may be some aspect of the flow across the rear of the body outline where the air flow at that particular point is increased by streamline convergence coming from both sides the top and the bottom, and the diffuser is set to correct some of that convergence so its further behind the car thus removing its effect from the body

kind of like the opposite of a scram jet that would take air going into an intake and compress it so it can burn way fiercer

i guess turning or 'veering' at very high velocities the wind shear on the back of the bumper could be murder