Understanding Formula 1: Diffuser and Exhaust

In modern day F1 cars, diffuser is the main area of focus and most of the teams spend millions of dollars to optimize the diffuser design. So, let’s take a look at how diffuser’s actually work.

To understand the working of the diffuser, we first need to understand how aerodynamics work on an F1 car.

The basic principle of aerodynamics is to create downforce and reduce drag, though both downforce and drag are inversely related. So, the teams have to find a balance between downforce and drag and this balance shifts, depending on the nature of circuit.

The rear wing creates downforce by creating an area of high pressure above the car. This high pressure pushes the car down, thus generating downforce.

The diffuser also functions on the same principle. There are two main functions of a diffuser:

• To pull the air from underneath the car, thus creating a low pressure and,
• Generate “Venturi Effect”: According to “Venturi effect”, the speed of airflow is faster, when the channel through which it flows, is constricted.

Let’s try to understand the above two points with the help of this diagram. As you can see, air is being pulled from beneath the car and is being blown upwards.This upward blow of air along with updraft of air, created by the rear wings, increases the pressure above the car.

Simultaneously, the pressure below the car decreases which creates a suction effect. This suction effect produces downforce and provides stability.

The second point is very simple to understand. According to the laws of aerodynamics, an object will move faster if the airflow through it is smooth, streamlined and fast. And due to the constricted area of the diffuser, the air flow through it is very fast.

The faster airflow also produces low pressure beneath the car, thus generating more amount of downforce.

So, speaking in layman’s term, the diffuser basically creates a high pressure above the wing and low pressure beneath the car, which pushes the car down and this generates downforce.

Recently, teams have developed exhaust blown diffusers. These also work on the same principle, the only difference is that instead of air from beneath the car, the exhaust gases get blown up over the wing which generates similar pressure levels.

The diffuser’s came to the fore in 2009 when Brawn GP pioneered what is now called double-deck diffuser. The double deck diffuser is now banned and the teams can only use a simple diffuser or Exhaust blown diffusers.

This year, FIA has banned the use of off-throttle Blown Diffusers. The Off-Throttle blown diffusers continued to blow exhaust gases over the diffuser even when drivers were off-throttle. Off-Throttle blown diffusers were the main reason for Red-Bull’s success in 2011.

Coanda Style Exhaust:

Recently, many teams have adopted Coanda styled exhaust. So, let’s see it’s functioning.

The Coanda style exhausts guide the hot exhaust gases to the rear of the car, which is then channelled above the rear wing through the diffuser, thus creating downforce. Along with the DRS system, it significantly improves the aerodynamic efficiency.

The Coanda style exhausts come with advantages and disadvantages. They help generate large amount of downforce at the expense of horsepower.

This exhaust has been developed in response to the rule changes for this year, which make it difficult for the teams to generate downforce levels generated by them during 2010 and 2011.

So, most of the teams have adopted the Coanda exhaust to compensate the downforce loss. Sauber was the first team to come up with this idea, which was then copied by Red-Bull, Ferrari, Mercedes and now, Lotus.