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F1 Car Diffusers: What They Do & How They Work

Diffusers have long been part of the technical talk of Formula 1 cars. For a long time, these elements have been the main “ground effect” component used on a Formula 1 car. However, with changing F1 regulations, F1 car diffusers have changed a lot over the years.

F1 car diffusers work essentially as a way to create a big difference in pressure underneath the car, helping to generate downforce. Diffusers diffuse the low-pressure, fast-moving air from underneath the car into the higher-pressure air behind it, providing downforce while minimizing drag.

Over the years, the design of the diffuser has been restricted to prevent teams from generating much downforce using the floor. Below, we’ll discuss what a diffuser is and the history behind this very important part of a Formula 1 car.

What Is A Diffuser In F1?

A diffuser on an F1 car is a section at the back of the car. It can be found underneath the rear wing in between the two rear tires. The diffuser looks like a large scoop at the back of the car with multiple fins attached to it, also known as stakes. It creates downforce for stability and grip.

Diffusers can differ from car to car, and it all depends on how they interact with the rest of the floor and the rear wing of the car. Each car has its own needs based on the design that has been implemented in building the car.

Diffusers have long been an area of interest in F1, and there was a massive “diffuser race” from 2009 until 2014 as teams were developing their diffusers by finding loopholes in the rules. The teams that got this concept right managed to build dominant cars (Brawn GP in 2009 and Red Bull in 2010), purely based on the downforce their diffusers were able to produce.

The Floor Of A Formula 1 Car

In order to understand how the diffuser works and why it is so essential on a Formula 1 car, we first need to understand how the floor of the car works. The floor can be used to generate downforce, even without the ground effect, which we’ll discuss in more detail shortly.

Even with a flat floor that is low to the ground, like that of F1 cars before 2022, the underside of the car is still crucial for aerodynamics. The best way to produce downforce using the over body downforce concept is by creating a low-pressure area underneath the car and a high-pressure area on top of the car.

Pressure Differences

This pressure difference essentially allows the high-pressure air above the car to push it into the ground. This is a very basic explanation of over body downforce in Formula 1, but we’ll get into the more technical aspects of it soon.

However, simply having air flowing underneath the car does not create low-pressure air to help the cars produce downforce. In order to create this low-pressure area, the air needs to be sped up using constrictions, using something called the Venturi effect.

The floor of the car being low to the ground squeezes the air underneath it, increasing its velocity and decreasing its pressure. But when this air gets to the back of the car, the diffuser allows it to gradually return to approximately atmospheric pressure in a way that minimizes turbulence. It does this by being shaped like an upside down scoop.

What Does An F1 Diffuser Do?

An F1 diffuser creates a transition section between the fast moving, low-pressure air under the car and the slow moving, high-pressure air above it. It allows the air moving under the car to expand – or diffuse – out the back of the car in a way that creates a lot of downforce.

Without this scoop-like diffuser, the low pressure air would rush to the back of the car, then meet the higher pressure air at the rear, generating turbulence and a ‘separation’ of air.

This separation of airflow can be thought of as generating a vacuum behind the car. An F1 car has quite a complex structure at the rear. One major component is the rear wing, and this is a separate downforce generating component that relies on the creation of a pressure difference in much the same way as other downforce generating parts of the car.

Minimizing Drag

With high pressure above the rear wing and low pressure below it, it generates downforce. But this leaves a low pressure area behind the rear wing as well, which is almost like having a vacuum behind it, trying to suck it backwards. This effect is known as drag, and teams want to maximize downforce while minimizing drag.

The diffuser helps here, as it ‘slowly introduces’ the fast moving, low-pressure air below the car to the slower moving high-pressure air above the car. If the two suddenly came together, there would be a lot of turbulence and airflow separation, both of which lower the amount of downforce the car can generate and increase the amount of drag trying to pull it backwards.

The Right Diffuser Angle

The steeper the diffuser angle, the more downforce the car can generate as the air behind the car returns to atmospheric pressure faster. However, with too steep a diffuser, the airflow is still moving fast enough that it can separate from the diffuser, leading to a vacuum area of low pressure that increases drag. The same thing happens with too steep a rear wing.

So, finding the optimal diffuser angle requires lots of calculations and design iterations, with time spent in the wind tunnels and using computer programs before the car is built to decide how best to maximize the car’s downforce while minimizing drag.

How F1 Car Diffusers Have Changed Over The Years

Diffusers are not a new concept in F1. However, they have changed dramatically over the years. Diffusers have been relatively basic ever since the ground effect was banned in the early 1980s. The diffuser was simply there to help the car generate more downforce.

However, as the 2009 rules brought in a major aerodynamic overhaul, the teams got into a diffuser arms race. The sport’s best engineers came up with incredible designs that had never been used before, which led to some of the most incredible and strongest Formula 1 cars being built despite F1’s efforts to make them slower.

Double And Blown Diffusers

2009 saw the double diffusers being implemented. Shortly after, blown diffusers were used. Both diffusers were born out of loopholes teams discovered in the rules. The FIA moved quickly to ban them from the sport though, and they have not been used since. We’ll take a closer look at each of these below.

With the 2022 rule changes, the importance of diffusers has become a huge talking point once again. With the ground effect back in place, the entire floor of the car essentially becomes one big diffuser in theory, but there’s a noticeable difference to the diffuser at the back of the car. We’ll talk more about this shortly. First, let’s look at the double and blown diffusers.

What Was The Double Diffuser In F1?

Brawn GP (now Mercedes) used the double diffuser to skirt regulations after discovering a loophole in the rules. A double diffuser is one diffuser inside another, which creates a tremendous amount of downforce, which allowed Brawn GP to dominate the early part of the 2009 F1 season.

Because of the 2009 rule changes, teams rushed to see how they could find a loophole in the rules to build the best car. Formula 1 regulations are written in such a way that they can be interpreted in many ways, which is why we tend to see such unique designs on the Formula 1 grid, like Mercedes did most recently with their DAS system in 2020.

Loopholes In The Rules

Brawn GP, however, was the first team to discover a loophole in the rules in 2009, and it was a big one. The team turned up to preseason testing with a double diffuser, which is essentially a diffuser inside another diffuser. The loophole in the rules meant they could create a second channel for the fast-moving, low-pressure air under the car to exit at the rear much faster.

Essentially, as long as it wasn’t visible from the rear of the car, the teams could design a hole a little further forward on the floor of the car that channeled the air up and out of a second ‘top deck’ diffuser much sooner than the regulations were designed to allow. Allowing the air to expand out at the rear much sooner allowed teams to generate much more downforce.

This meant the Brawn GP car, and to a lesser extent Toyota and Williams’ cars, had massive amounts of rear downforce, making it much more stable and allowing it to corner much faster than other cars. The results spoke for themselves, as Brawn GP won 6 out of the first 7 races in the 2009 season.

Protests

As the Brawn GP car lit up the timing screens during preseason testing and dominated the Australian Grand Prix, the other teams were quick to protest the double diffuser loophole that the team had discovered. However, the double diffusers were declared legal.

Other teams quickly followed with their own adaptations of the double diffuser, suggesting they were working on their own even when protesting the Brawn GP concept. However, Brawn GP was already a few steps ahead of the competition.

Other teams were never truly able to match the Brawn GP double diffuser concept. The Red Bull team was the only team to come close to challenging for the titles in 2009, but by that point Brawn had already done enough. McLaren also made major improvements, but no team was able to match Brawn GP. The double diffuser was banned by the FIA for the 2010 rule changes.

What Was The Blown Diffuser In F1?

The blown diffuser worked by positioning the exhaust to allow the gases to be forced through the diffuser. Pushing the exhaust gases into the diffuser meant that even more air was rushed through the diffuser, creating more downforce than a normal diffuser.

In 2010, the double diffuser was outlawed by the FIA, which meant that teams could no longer use the concept of building a diffuser within a diffuser. However, after realizing the power of the diffuser, teams set out to find more loopholes.

Red Bull knew that the blown diffuser would be a huge success and therefore tried to disguise their concept using stickers in the old exhaust position to throw off their opponents.

Formula 1 engineers are too smart for that though, and the concept was quickly adopted by other teams. However, they never truly caught up to Red Bull as they continued their development of the blown diffuser. Red Bull had one secret weapon that kept their blown diffuser one step ahead of the rest, and that was their powerful Renault engine.

History Of Blown Diffusers

This time it was Adrian Newey and Red Bull who led the way with the blown diffuser. The blown diffuser was not a new concept though. Cars throughout the 1980s and 1990s, such as the Renault RE40 (1983) and the McLaren MP4-7a (1992), used blown diffusers.

However, there was a huge design flaw on these blown diffusers that teams simply could not overcome, which is why they eventually fell out of favor in Formula 1. Teams would place their exhausts inside the diffuser, making it less effective since the air was not rushing through the diffuser fully, but only out of the end of the diffuser.

The other major flaw was that the cars’ engines would only produce exhaust gasses while the driver was on the throttle. This means the car had most of its downforce when the throttle was pressed down on the car, and this resulted in many drivers having to adapt their driving style.

Drivers had to press down on the throttle while cornering in order to get more downforce at the rear of the car. This required a delicate balance, as too much acceleration would cause the car to spin, and not enough acceleration would also cause the car to spin from a lack of rear downforce.

How Did Red Bull Improve The Blown Diffuser?

Adrian Newey was happy to revisit the idea of a blown diffuser, however this time he had a plan to make it work even better than before. By making some slight adjustments he was not only able to make the blown diffuser produce more downforce, but also constant downforce.

The first thing that Newey did was place the exhaust slightly in front of the diffuser and close to the floor of the car. Newey then worked with Renault to solve the issue of having to be on the throttle for the car to produce exhaust gases to blow through the diffuser and produce downforce.

This would remove the need for the drivers to be always on the throttle for the rear of the car to generate downforce. Renault mapped their engines in such a way they would still produce exhaust gases even if the driver was off the throttle. The result was a blown diffuser that generated massive amounts of downforce, and it could do so all the time whether the car was accelerating or not.

The Blown Diffuser Was Not Banned

The blown diffuser was never technically banned from Formula 1. In 2011 all teams adopted the concept, and seeing as so many teams had spent money developing the blown diffuser, the FIA did not ban it from the sport.

However, the FIA did want to limit how powerful the device was in producing downforce at the rear end of the car. What they did instead was alter the rules as to where the exhaust outlet could be placed. In 2014, the engine regulations changed to the V6 hybrid formula, and with exhausts placed on the car’s center line, the blown diffuser was no more.

How Are The 2022 F1 Car Diffusers Different From Previous Years?

The 2022 F1 rule changes brought about a major overhaul to the diffusers on the cars. The diffusers look significantly different from previous generations, and the return of the ground effect in F1 meant that diffusers had to become much bigger and are far more visible at the rear of the cars.

Instead of a subtle diffuser with small rakes on the floor of the car, the 2022 cars have massive diffuser outlets at the back. These essentially let the air expand out of the rear of the car much faster, which is essential given that the ground effect requires more air to be pushed underneath the car to generate downforce, and this larger volume of air needs a bigger diffuser to escape.

The use of the various tunnels underneath the car, and the overall shape of the car, essentially means the entire car functions as one big diffuser. It takes on a kind of scoop shape, with lots of fast-moving, low-pressure air channeled underneath it to generate downforce via a kind of suction effect. This, by nature of more air going underneath the car, requires a larger diffuser at the rear.

Final Thoughts

F1 car diffusers are underneath the rear wing and are used to essentially pull air underneath the floor by constricting the airflow and then expanding it at the rear of the car, causing a suction effect and generating downforce. F1 car diffusers are important downforce generating components.