Dirty air and clean air are two common terms used in F1. They are used to describe the way the air flows around the cars, and they each have big implications on their aerodynamics. But what exactly is dirty air?
Dirty air refers to the air coming off of an F1 car as it drives around the track. This air is turbulent and often hot, as it has passed over, under and around the body of the car. Any car close enough to the car in front produces less downforce in dirty air as ‘clean’ air is ideal for aerodynamics.
The 2022 rule changes improved the dirty air problem that Formula 1 has experienced for many years, and the cars are now much easier to follow than those from 2021 and earlier. However, dirty air has not been completely eliminated from the sport, so I’ll explain everything you need to know about it below.
What Is Clean Air In F1?
Clean air is undisturbed and can easily move along an F1 car’s body and through the air intakes. This allows cars to produce maximum downforce in clean air, and cool their internals more efficiently. Clean air is the ideal situation for a Formula 1 car’s aerodynamics.
As the clean air passes over a Formula 1 car it ‘pushes’ the car into the ground, through the effect known as downforce. With the 2022 aerodynamic rule changes, the air is also pulled in through the Venturi tunnels underneath the floor of the car. This means the floors of the modern cars produce a larger proportion of the cars’ downforce than in the years leading up to the rule changes.
Clean air is therefore ‘better’ in Formula 1, as each aerodynamic part of the car can produce maximum downforce and the car can cool itself more efficiently too. The latter is true because, as I’ll discuss more below, clean air is also cooler than dirty air, and for efficient cooling you need a large difference in temperature between the hot components (like the engine and brakes) and the air flowing over and through them.
Producing Downforce
But going back to downforce, in order to produce any at all, F1 cars need an area of high-pressure air above them and an area of low-pressure air underneath. It’s this pressure difference that causes the car to be ‘pushed’ or ‘sucked’ towards the ground.
In clean air, when a car doesn’t have another one in front of it, it’s easy to generate this pressure difference as there is a lot of air in front of the car in a fairly uniform arrangement. But when this air is moving around chaotically, or turbulently, the car isn’t able to generate as much downforce as before. This is the issue of dirty air.
What Causes Dirty Air In F1?
Dirty air is caused by an F1 car moving through clean air and disrupting it, making it turbulent and lower in energy. With all the wings and various other downforce-producing components on an F1 car, the air is greatly disturbed, and because F1 cars travel so fast, the wake of dirty air is measurable even several seconds behind.
It’s difficult to imagine since we can’t see how air moves when a car goes through it, but it’s similar to the way a boat moves through the water.
The Wake Of An F1 Car
When a boat moves through the water, you can see the wake behind it. The wake behind a boat is like the dirty air or turbulence that you would find behind an F1 car as it moves through the air. The wake is simply caused by the boat moving through the water, disturbing it as it does so.
If you add little winglets and change the shape or size of the boat, you can change how much of a wake follows behind it. This also changes how far the wake extends behind it. Formula 1 cars work in the same way when it comes to dirty air and the wake that they have behind their cars.
The previous generation of cars used complex wings with unique shapes and different aerodynamic parts on their body. This gave the cars more downforce, but it also left a massive wake around and behind them with a long trail, meaning that cars behind them were not able to follow closely, and even those several seconds behind would lose some downforce.
Key Fact: Dirty air doesn’t just come off the back of F1 cars. They also generate outwash, which is effectively dirty air thrown out to the sides and over the car, as well as out the back, via the exhaust (hot air from the engine) and the diffuser.
Once the air passes over a Formula 1 car it becomes turbulent. This is because the clean air is used to push the car into the ground (or ‘suck’ it towards the ground in the case of the ground effect). The various wings and other components on the car disrupt the air as they ‘use’ it to produce downforce or direct it in various ways, and this leaves a trail of dirty, turbulent, low-pressure air behind the car.
Low Pressure, Low Energy
This air is sometimes referred to as low energy too, and we can think of the air’s energy as its total pressure (static + dynamic). Air hits the front of the car with maximum total pressure, but as it goes over, through and around the various components on the car, it’s pressure decreases, and this is sometimes referred to as ‘loss.’ This is why you might sometimes hear aerodynamicists talking about ‘reducing losses.’
I use the term ‘low-energy’ because air can be both turbulent and high-energy (as is the case with some of the vortexes produced by the cars), but it’s low-energy turbulent air that is the ‘worst’ for downforce production. So, just saying turbulent isn’t always enough when we’re discussing dirty air.
So, the air that is left behind is of lower energy, and the car behind can’t get as much downforce out of it. This is a big simplification, but hopefully it helps visualize why dirty air is such a problem for the car behind.
Let’s take a closer look at how dirty air affects F1 cars.
How Does Dirty Air Affect An F1 Car?
Dirty air is what makes Formula 1 cars difficult to follow through the corners, as the cars are not able to produce as much downforce in dirty air as opposed to clean air. The main focus of the 2022 aerodynamic rule changes was to make the cars easier to follow. But why is this important?
The biggest strength that a Formula 1 car has is the massive amount of downforce that it can produce. Formula 1 cars produce more downforce than any other race car on the planet, and this is what makes them so incredibly fast across an entire lap. Nothing can beat the cornering speeds that Formula 1 cars can reach.
Formula 1 cars can take some corners at 190 miles per hour (305 kph), and the faster you go, the more downforce the car can produce (there is of course a limit, largely due to increasing drag forces at higher speeds, but we can ignore that for this discussion). However, the car needs clean air in order to produce maximum downforce.
They Can Still Produce Lots Of Downforce
The car is still producing lots of downforce (it doesn’t drop to nothing out of nowhere), but the aero balance of the car fluctuates in dirty air due to the uneven pressure of the turbulent air the car is driving through. The upset aero balance makes the car more difficult to control, and the driver has to ‘fight’ the car more to keep it on the track. They may start sliding slightly in the corners, which makes the tires wear faster.
The engine of a Formula 1 car is extremely hot. The heat from the engine is ejected at the back of the car through the exhaust, and mixing this hot air with the turbulent air coming off the wings and other components makes for even ‘dirtier’ air. It also makes it harder for trailing cars to cool their internal components too.
Cooling The Car In Dirty Air
In order to cool something down, you need to surround it with something that’s of a lower temperature. Heat flows from hot to cold, and in F1 this means heat flows from the engine (and other hot components like the brakes) to the cooler ambient air that passes through the radiators and brake ducts.
This means the air temperature affects how well F1 cars can cool themselves, and in hotter climates the cars won’t cool themselves as efficiently. We also see F1 cars struggle to cool themselves at high altitudes, where the air is less dense, such as at the Mexican Grand Prix. This is effectively what it’s like running in dirty air: lower density + higher temperature = poorer cooling capabilities.
Note: You can learn more about how this works in our article on F1 car cooling systems
F1 Slipstream vs Dirty Air
Dirty air is not always bad for Formula 1 cars though. When it comes to the straights, less downforce is actually better. This is because while F1 cars produce downforce, they also produce drag, a force that ‘pulls’ them back, limiting how fast they can go. This means that the same turbulent air that disrupts the car through the corners can actually benefit the trailing car on the straights.
A slipstream in F1 (sometimes called a ‘tow’) is when one car follows closely behind another car, allowing the following car to gain speed without having to ‘work’ harder. Slipstreams are incredibly powerful in Formula 1 because of how the car’s aerodynamics work, so the following car could easily gain more than 10 mph in a slipstream on a long straight (16 kph).
Slipstreams work when the lead car ‘punches a hole’ in the air for the car behind, leaving behind them an area of lower pressure, less dense air. The car behind, when tucked in behind the car ahead of them, has much less air resistance that it needs to cut through, which means that it can hit a much higher top speed than it could in cleaner, denser air. This gives the effect of being towed along by the leading car.
Slipstreams are not always powerful though, and the cars often need a long straight in order for them to work. On circuits with shorter straights, such as in Monaco, the slipstream is not as effective as on circuits like Monza and Spa. Plus, there is still the issue of cooling, as this turbulent, low-pressure air is poor for cooling on straights and in the corners.
Clean Air vs Dirty Air In F1: A Summary
A summary of clean air vs dirty air in F1:
- Clean air in F1 is preferred to dirty air in most racing situations, with the exception being on straights, where it is often used to slipstream the car in front.
- Clean air is best for downforce production, and for cooling an F1 car.
- Dirty air makes it harder for F1 cars to follow each other, as it limits the amount of downforce trailing cars can produce and how effectively they can cool their internal components.
Has Dirty Air Always Been A Problem In Formula 1?
Dirty air is nothing new in F1, and it has been around in a large scale since at least the 1980s. Cars in the late 1990s and early 2000s were likely losing up to 30% of their downforce as a result of dirty air. But things took a bigger turn in 2009, when rules brought in to solve some aerodynamic concerns led to teams creating large amounts of outwash.
Cars started producing bigger wakes than before as front wings and bargeboards pushed the wake from the front wheel as far away from the car as possible to avoid them interfering with the car’s aerodynamic components further back. As the cars got ever more complex over the years that followed, with intricate winglets and complicated bargeboards, the mushroom-shaped wake that the cars left behind them got larger.
In order to improve the racing, it was clear that two things had to be achieved:
- The wake had to be reduced
- The cars had to become less sensitive to dirty air
So, for the 2022 F1 season, the aerodynamic regulations were changed in an attempt to make the cars easier to follow.
How Do The 2022 Rule Changes Improve Dirty Air?
Removing all the winglets and bargeboards from the cars and creating simpler wings as a result of the 2022 rule changes reduced the amount of turbulent air thrown off and around the car to make following easier. But it also made the cars less sensitive to dirty air. For example, bargeboards were powerful downforce producers, but they were highly sensitive when driving through a wake, so they were banned for 2022.
Simplifying Some Components
The complex front wings that produced massive amounts of outwash (helped by something called the ‘Y250 vortex’) were also very sensitive to the turbulent air. Lower-drag wings were also introduced to help with the wake sensitivity, as these produce less disturbed air and more aerodynamic resilience when following other cars. The wing shapes now feature smoother lines to reduce the amount of dirty air produced, and the front wing in particular produces less outwash than before.
Further management of the tire wake was achieved by changes to the front brake drums, and the wheels are now covered, also featuring wake deflecting fins above them. All this improved the airflow around the high disturbance area around the wheels and reduced the lateral wake (this makes it easier to pull alongside a car ahead), and more of the rear wake was sucked inboard.
F1 had to make some more changes to the cars to allow them to simplify these components while also letting the cars produce the necessary amounts of downforce that allow for such high-speed racing.
Venturi Tunnels & The Beam Wing
One implementation you’ll hear a lot about are the Venturi tunnels. These allow the cars to make use of the ground effect, and they’re also less sensitive to dirty air as the losses (in turbulent air) are constant at both axles, allowing for a more consistent aero balance (and an easier time for the trailing driver). You can learn more about these in our full guide to Venturi tunnels in F1.
In order to direct dirty air away from the floor of the trailing car, the beam wing was brought in. The beam wing is the smaller wing underneath the rear wing, and the goal of the beam wing is to direct some of the dirty air up and over the car behind, leaving more clean air available for the following car to use to produce downforce.
All of these measures meant that the mushroom-shaped wake was now more teardrop-shaped, largely directed upwards over the following car. The downside here is that the slipstream effect is therefore somewhat reduced, but as we see in every race, especially wet races without DRS, the slipstream or tow in F1 is still incredibly powerful.
The 2022 Regulation Changes
When the 2021 cars followed each other within about 20 meters the estimated downforce loss was 35%. This meant that the trailing cars couldn’t reach their theoretical top speed in the corners as they lost some downforce and would have to trail further back just to stay in control of their car at these speeds.
The 2022 regulations aimed to reduce this effect substantially, and early estimates suggested that the downforce loss that was once 35% is now just 4%. However, the closer the cars get (to a certain extent) the more powerful the dirty air effect becomes, and it is an unavoidable consequence of open wheel racing.
Key Fact: The downforce lost when 1 car length behind the car in front is now about 14%, but pre-2022 it was as much as 45%
Is Dirty Air Still A Problem In F1?
The dirty air that comes off of a Formula 1 car has significantly reduced following the big rule changes that were implemented in 2022. However, it is still somewhat of an issue in modern Formula 1, and the cars still sometimes struggle to follow one another. But there is no doubt it’s much better than it was in and before 2021.
We have seen that it has become much easier for the cars to follow each other more closely, especially when we look at the various battles that we have seen on track. Some of the overtakes that were pulled off in 2022 would have been nearly impossible in 2021 and earlier.
The main difference that we are seeing is that drivers now have the ability to fight back when they are overtaken by another car. In the past, a driver had to back off as soon as they had been overtaken because of the huge loss of downforce that they would experience in the wake of the car ahead of them.
However, as saw with Max Verstappen and Charles Leclerc at the early part of the 2022 season, battles can rage on for several laps and drivers don’t quickly fall back in order to regain their grip. It’s a positive sign, but more work needs to be done and the cars need to be tweaked more in order to promote further overtaking opportunities in Formula 1.
At the end of the day, it’s open-wheel racing, and these cars will always have problems with dirty air. It’s an unavoidable consequence of the car designs. However, it’s clear that the 2022 regulation changes had a very positive impact on the dirty air situation.
Final Thoughts
Dirty air in F1 makes it difficult for cars to follow each other, and for many years it has prevented cars from overtaking with ease. However, the effect of dirty air has improved, and we are seeing more competition between drivers as they can follow each other without losing as much downforce.
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