Originally Posted by Octoman

Hmmm..... What is a splitter? Can someone identify it for me and what does it do?

Originally Posted by johng

This may or may not be helpful, and the following information is borrowed from another source.



A splitter generates downforce on the front of a car by creating pressure differentials. 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. But that is really just semantics.

This picture 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 air flow 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. Most people are well aware of this already.

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.


Some racecar designers have maximized the use of a front spoiler venturi.



If we examine the spoiler on the 1996 DTM/ITC Mercedes Benz shown above we notice that it does not have any kind of splitter. In fact, it has the opposite of a splitter. The lower portion of the spoiler curves back in towards the car, instead of jutting out into the stagnation region. The designers were trying to encourage the high pressure air in front of the spoiler to flow underneath the car. This way they could maximize the venturi effect underneath the front of the vehicle. In essence, the front spoiler region of the car forms a "mini ground-effect tunnel". In the "throat" region of the venturi, the air flow speeds up and hence the local pressure goes down. This creates downforce. The longer the throat region is, the more downforce that can be created. A simplified schematic of the air flow over and under a racecar with a spoiler venturi is shown below.



There are many possible permutations of the splitter/venturi spoiler idea. Some racecars use either just a splitter or just a venturi. Other designers have attempted to combine the two devices in an effort to maximize front downforce under modern racing regulations (which usually require a flat under-body from the front axle-line back).