Front splitters are essential aerodynamic components that serve to balance the front vs. rear distribution of downforce. Splitter is typically found on the front-end of a race car, appearing as a flat extension to the very bottom of the front bumper. This splitter extends straight out, parallel to the ground, and can be made of carbon fiber or other stiff material.
It is attached to the bottom of the front bumper, and may also be supported by two or more support rods at some distance forward of the bumper mounting points. These support rods ensure that the splitter stays parallel to the ground, even when there are outside forces around the splitter.
Front-end splitters on a race car produce aerodynamic downforce by creating differences in the air pressure on the upper and lower side of the splitter when the car moves.
To understand how a splitter creates downforce you have to know a few fluid dynamics. One should at least be aware of the difference between static pressure and dynamic pressure. It is also instructive to know how dynamic pressure is related to flow velocity. This relationship is given by the well-known Bernoulli equation. Though Bernoulli’s principle is a major source of lift or downforce in an aircraft or racing car wing, the Coanda effect plays an even larger role in producing lift.
When a car travels at high speeds, the air pressure in front of the car can become very high. The incoming air approaches the car at V1, which is the speed of air around the vehicle, and a pressure P1 which is related to V1 according to Bernoulli’s equation. P1 will be somewhat less than atmospheric. The essential point to be taken from Bernoulli’s equation is that the pressure inside an air stream is related to the velocity at which the air stream is moving.
All this air ends up going both above the car (over the hood), and below the car (under the front bumper). When too much of this air gets under the front bumper, the under-car air pressure builds up. This increased air pressure contributes to lift, which causes the front-end of the car to lighten up, reducing the amount of traction at the front of the car. This high pressure (and lower speed) air, when compared to the airspeed above the car, will create a situation where there is increased lift over the entire car. Typically, most production streetcars, when traveling at higher speeds (100km/h+) produce large amounts of positive lift.
What we want to have is lower pressure, faster-moving air below the car, and higher pressure, slower-moving air above the car. The lower pressure side, when it happens to be under the car, contributes to reduced lift. When the lift is reduced sufficiently to the point where there is a negative lift, there is net positive downforce.
As the airstream velocity goes up, the dynamic pressure within the air goes down. In simple terms – The air travels faster in the low-pressure area created under the splitter, and that “sucks” the car’s nose down, creating downforce and reducing understeer, especially on a track where you have fast-flowing corners.
The splitter itself does not actually create downforce. What the splitter does is that it increases the area over which high pressure can build up. The more high pressure there is above the splitter, the more low pressure is below the splitter, the greater the net downforce there is. Additionally, if there are openings in the front bumper (above the splitter or lip) for brake ducts or radiator cooling, this increased air pressure will encourage more air to flow into these openings.