Talk:NISSAN SILVIA (S15) R3 Spec Championship/@comment-26845160-20171206075133/@comment-62.154.199.77-20171206133159

The diffuser which you are refuring too is a device to create downforce.

Basically what it causes is that the surrounding air pushes the car into the groud as the pressure below the car is lower then around the car.

It works on 2 aerodynamic principles.

-Venturi -> ρ1*v1*A1 = ρ2*v2*A2 (density * velocity * area) since density will be the same for air the equation becomes

v1*A1 = v2*A2

- Bernoulli -> P1 + (1/2*ρ*v1^2) = P2 + (1/2*ρ*v2^2)

Venturi will determine the speed of the air below the car. Once the car passes the area below the car becomes much smaller compared to outside of the car. As you can see from the equation this means that the velocity of the air has to go up in order for the formula to remain even.

Now we move to Bernoulli. As you can see from the equation if the velocity is increased on one side, the pressure has to go down on that same side in order to compensate the formula agian. Thus explaining the pressure drop below the car.

A low pressure below the car will resort in less "weight" below the car. This means that the air surrounding the car is heavier pushing the car down.