Car Rear Diffuser: What Is It?

In recent years, there have been vast developments in car design. There has been more focus on creating an aerodynamically stable vehicle in which airflow is the most important feature. These changes in technology have enabled automobile engineers everywhere to make an aerodynamically suitable car by incorporating aero elements in its design, features that actually originated with racing cars. 

One of those key features is a rear diffuser, which can be found in both economic and luxury vehicles. Continue reading to find out the function and importance of this element, which may make you consider getting a diffuser.

What is a Car Rear Diffuser?

The main function of a car rear diffuser is to increase the vehicle’s downforce and increase its grip on the road surface, thereby reducing the aerodynamic drag. The air pressure beneath the car is affected by the diffuser, helping the air pressure regulate as the vehicle continues to move forward. It’s a very similar concept to an airplane wing or the rear spoiler of the car, as all of these make use of Bernoulli’s Principle to decrease the air pressure and increase the speed of the air.

How Does It Work?

As the car moves forward, air at high speed passes under the car at low pressure. When this low-pressure air reaches the rear of the vehicle through the diffuser, the air expands in a chamber. 

The Venturi effect happens as the air expands, in which the air pressure is increased, and the airspeed is significantly reduced. The difference between the high pressure at the rear and the low pressure under the car creates a vacuum that sucks the air out of the vehicle. And with low air pressure under the car and high pressure above it, increased downforce is therefore created, and aerodynamic drag is reduced.

Aerodynamic drag is when the vehicle cuts through the air as it moves, facing the wind from the opposite direction that reduces the car’s efficiency. Once the aerodynamic drag is reduced, the car’s performance goes way up.

On that note, an aerodynamic grip or downforce is a phenomenon that happens when increased air pressure is applied on any given surface. In vehicles, downforce creates traction between the tires and the surface of the road, enabling the car to remain stable. Most cars on the market nowadays are actually designed to provide a decent amount of downforce; however, a car rear diffuser is an excellent way to maintain superior downforce without compromising on performance.

Major Components of a Car Rear Diffuser

There are three important parts of a high-quality and functional car rear diffuser, which are the following:

• Vertical Fins

Vertical fins help the airflow maintain a smooth path (also referred to as laminar airflow) out to the rear of the car. Without these vertical fins, the airflow under the vehicle can become quite turbulent, which will affect the stability of the car. Laminar airflow is necessary in order to decrease turbulence and increase drag.

• Smooth Underbody

While this is not an inherent technical part of a car rear diffuser, it is a significant contributor to its efficacy. The smoother the underside of the car, the quicker the air flows to the rear, and the aerodynamic drag lowers significantly easier to work in tandem with the diffuser.

• Expansion Chamber

An expansion chamber is meant to create a difference in air pressure between the rear of the car and its underside. This difference in air pressure is what creates a vacuum that sucks the air out of the back and creates an aerodynamic grip.