Front Wing/Splitter/Diffuser

[Pennzoil GT-R]

I know the principle behind the front wing, and i know how the rear wing and diffusers work, but how do they work an fit into the front of a car?

[Gasoline Fumes]

Something I saved from another forum:
(I didn't write it)

Actually a splitter produces a "downward force". It is not technically termed "downforce" unless the downward force is large enough to overcome the "upward" force caused by lift.

This illustration shows that as the incoming air reaches the front of the vehicle it must come to a stop before it turns to move either up and over, down and under, or around the vehicle. The area where the oncoming airflow comes to a stop is termed the "stagnation point". Since the velocity has gone down, the pressure has gone up (the "stagnation pressure”). Thus the front of the moving vehicle is an area of relatively high pressure.

One of the realities of pressure is that it acts in all directions. Thus the relatively high stagnation pressure at the front of a moving vehicle pushes back on the vehicle creating drag. Now if we stick a splitter out on the bottom of the spoiler, then the stagnation pressure will also push down on the top of the splitter. But what is the pressure on the underside of the splitter? If it is the same as the pressure on top then there will be no force on the splitter. So let's examine the pressure underneath the splitter.

Since the splitter is close to the tarmac, it creates a restriction to air flowing underneath it (a mini-Venturi if you will). Just as water in a river speeds up when the river narrows, the air that is piled up in front of the spoiler must speed up if it wants to squeeze underneath the splitter. When an airstream speeds up, its pressure goes down. Thus the region between the splitter and the pavement is an area of low pressure. To recap; high pressure exists on top of the splitter, and low pressure exists beneath it. This adds up to a downward force on the splitter. And this downward force is directly proportional to the surface area of the splitter. So, up to a point, the bigger the splitter is, the more downforce it can create.

[SaabJohan]

You can find a lot of pictures on front diffusers here:
http://www.mulsannescorner.com/