THE INSIDER’S GUIDE
In this week’s Insider’s Guide, we will be highlighting the basics of air-flow: everything from how it affects your car to what you need to do in order to combat its disadvantages when following other cars, and how to use it to give yourself a tactical advantage.
One of the critical aspects to a number of different areas in racing is air-flow. Intriguingly, it’s not something a lot of drivers spend much time considering because you can’t really see it … and yet, as invisible as it may be, the repercussions of air-flow affect all sorts of elements in motorsport.
Let’s start with the basics: as a car drives along at speed, air flows along, around, under, and over the body-work and various aerodynamic parts on the car. Driving through air creates drag (which slows you down) but what comes with drag is downforce. Typically, the more drag you produce, the more downforce you will produce and in this way you trade higher top speeds for more grip in the corners.
As a car passes through the air, it also leaves an area or pocket of air behind: this air is momentarily disturbed and uncontrollably moving around all over the place until it settles again (which is why it’s known as “dirty” air). The faster a car travels and as speed increases, the larger this area of disturbed air becomes.
When a car drives into this area of disturbed air created by the car ahead, it will be affected in a completely different way than the car it whose wake it is travelling: This is where two main terms come in:
- Slipstreaming: This has a positive impact on the car behind.
- Dirty Air: This has a negative impact on the car behind.
Both terms are effectively the same sort of thing but happen at different points around the circuit.
Slipstreaming typically describes a car that is following another car closely and tucking into the pocket of disturbed air. At this point, the trailing car experiences a minimization of drag and air flowing over their own car. Lower drag then means higher top speed, and this allows the chasing car to accelerate faster and gain a speed advantage on the car in front.
Spending more time in the slipstream of an opponent will see a larger speed differentiation between the two cars, increasing the chance of a successful overtaking move.
Dirty Air is typically used to describe the area of disturbed air that trails in the wake of a car and through which the chasing car must travel, particularly through a corner of series of corners. Because the air isn’t stable, the efficiency of the air flowing over the bodywork and aerodynamic parts of the following car is reduced, meaning it has less available grip through the corners.
How big the effect of Dirty Air and Slipstreaming depends on a number of factors:
- The type of cars racing: A high-downforce car such as a Formula A or LMP1 car is going to punch a much bigger “hole” in the air, meaning the effects of slipstream and dirty air are much stronger. A low-speed car that doesn’t rely on downforce, i.e., a Renault Clio Cup car, for instance, isn’t going to produce as big an area of disturbed air, so the effects of dirty air and slipstreaming are going to be much lower.
- The number of cars racing: The more cars that are in front of you, the more the air is going to be disturbed. Being at the rear of a pack of a cars is going to reduce the efficiency of air flowing over your car in comparison to following just one car.
Dirty air, though, won’t just affect your handling, it also has the potential of affecting both your braking ability and your engine temperatures.
Engine temperatures might increase a little higher than normal when running in close behind another car. The impact is small and might not be overly noticeable, but it is there, so keep an eye on oil and water temperatures to make sure they don’t get too high when racing in close behind someone.
The impact on braking will be more noticeable. You won’t have as much clear air flowing into your brake ducts, meaning they will heat up more under braking and won’t cool as much on the straights. You also don’t have the same amount of drag hitting the front of your car that generally serves as a kind of invisible “parachute” in high-downforce cars, meaning that it can be easier to out-brake yourself: the consequences of that, as you chase the car ahead, can be catastrophic—nose-diving into the car you’re chasing. To avoid this, adjust your braking by getting on the brakes 5-10 metres earlier than normal.
With higher-downforce and faster cars, you may need to run a slightly different line to the car in front to slightly poke your car out of the dirty air in order to get the air-flow back over your own car, particularly through the highspeed bends. Obviously dropping back a few car lengths will also help, but isn’t necessarily optimal if you want to slipstream your opponent and attempt to make a pass on the next straight.
Finding the balance between the two is tricky, but it is something that the pros always have in mind, either thinking about it and adjusting accordingly, or adjusting their driving subconsciously.
So sit back and get into the cool air as Yorkie065 explains with the aid of and some visual examples how air-flow affects your racing in this week’s Insider’s Guide to Project CARS 2.