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Rear Diffuser

It is not enough that your car creators ludicrous amounts of power and torque. Going fast does not rely on sheer power alone. There is also an unseen property called aerodynamics, and a rear diffuser uses aerodynamics to improve the performance of your vehicle

A Lesson in Aerodynamics

Aerodynamics is the study of the properties of moving air and the interaction between the air and solid bodies moving through it. One component of aerodynamics that occurs both inside and outside the car is the rear diffuser.

What is a Car Rear Diffuser?

In automotive terms, a diffuser is a shaped section of the car’s underbody that improves the vehicle’s aerodynamic properties. This happens by enhancing the transition between the high-velocity airflow underneath the car and the freestream airflow of the ambient atmosphere. In simpler terms, the purpose of a rear diffuser is to reduce air turbulence as your car drives at high speeds.

How Does a Rear Bumper Diffuser Work?

As a vehicle is driven down the road, high-speed air is passing underneath the vehicle at low pressure. As the air passes to the rear of the vehicle through the diffuser, the air expands through an expansion chamber. Through this expansion, airspeed is reduced and pressure is increased. This is called the Venturi effect, and this pressure differential between the low-pressure air under the car and the high pressure at the rear creates a vacuum that sucks the air out from under the car. With high-pressure air above the car and low pressure under the car, high downforce is created while reducing aerodynamic drag. Aerodynamic drag is the force of air pushing in the opposite direction of the vehicle, reducing efficiency in the process.

Imagine the comparison between the front of a semi-truck, which is mostly flat and tall, compared to a sports car’s low and pointy front. The semi-truck has a greater surface area pushing against the air as it moves forward, preventing the vehicle from efficiently moving through the air. More power is needed to overcome this negative force, creating inefficiency.

By decreasing drag, rear diffusers make your car more stable at high speeds and reduce the amount of wind resistance it must overcome. Less wind resistance means that your vehicle will be able to utilize its existing horsepower and torque more efficiently. A universal rear diffuser also adds an even more aggressive style to your car which helps it stand out from the crowd. 

What Are the Different Diffuser Positions?

A diffuser can be positioned either in the front of the car or the rear of the car. Both diffuser positions have the same task, which is to reroute air away from the car to reduce drag and increase power and torque. When deciding between a front or rear diffuser, it depends on the make and model of your vehicle, as well as a few other factors. You should consult an expert to see if a front diffuser may work better for your car than a rear diffuser.

What Type of Material is a Rear Diffuser Made Of?

Rear diffusers are typically made up of one of four different types of material. Most diffusers are made of either carbon fiber, fiber-reinforced plastic, titanium, or stainless steel.

Carbon Fiber Diffuser

A carbon fiber diffuser is the most popular type of diffuser on the market, providing a very strong yet lightweight material. 

Fiber-Reinforced Plastic Diffuser

Fiber-reinforced plastic, also known as FRP, is a material that is a composite of polymer reinforced with fibers. FRP is also very strong and lightweight, meaning it will not add much weight to your vehicle and still give you excellent results. 

Titanium Diffuser

Titanium is a metal that combines outstanding strength with low density. The element is silver in color and is commonly used in car engines.

Stainless Steel Diffuser

Stainless steel is an iron alloy that is 10.5% chromium, which helps prevent the steel from rusting or corroding. This makes stainless steel incredibly durable and reliable.


Does a Rear Wing Change the Way a Rear Diffuser Works?

Having a rear wing on your car also affects the function of the diffuser. When the rear wing is mounted low and close to the diffuser, the low pressure under the wing helps suck air through the diffuser.

Installing an Inlet and Splitter With a Rear Diffuser

As the front of a vehicle slows down the air without a diffuser, this is the ideal place to install an inlet. A splitter is commonly used and it serves to increase the amount of downforce (lift inverted) at the front of the car. The airstream is brought to stagnation above the splitter by an air dam, which results in an area of high pressure. Below the splitter, the air is redirected away from the stagnation zone and accelerated, causing the pressure to drop. The decrease in pressure in combination with the high pressure over the splitter area creates a downforce. Consequently, the larger the area of the splitter, the more downforce is generated.

Purchase a Premium Rear Diffuser From Vivid Racing

If you are interested in adding a rear diffuser to your vehicle, Vivid Racing can help. You can either buy online or call us today to place your order. If you don't see what you're looking for, please contact us at 1-480-966-3040. We can help you find the right product for your vehicle to fit both your taste and your needs.