A guide to blown diffusers

On a modern F1 car the floor and diffuser are responsible for generating around 40% of the downforce. So it’s little wonder that F1 aero departments spend so much time refining their floor designs in the never-ending quest for downforce. This year, of course, the floor has been grabbing more headlines than usual with several teams using floors that channel the exhaust gases through the diffuser – the aptly named ‘blown diffuser’. The Renault F1 Team introduced its version of the blown diffuser in Valencia two weeks ago, and both R30s raced with this must-have upgrade in this afternoon’s race.

To explain more about how the blown diffuser works, we caught up with Renault F1 Technical Director, James Allison, for a quick guide.

James, what is a blown diffuser?

A blown diffuser is simply a diffuser that is energised by putting the exhaust flow into the diffuser and blowing it with the exhausts.

Why does it create more downforce?

A standard diffuser works by creating low pressure underneath the car, which helps suck the car to the ground. So by using the energy in the exhaust, which is a very fast moving stream of gas, and blowing it over a curved surface, you can create a much lower pressure under the floor and create more downforce.

What are the main challenges of getting an effective system?

The first challenge is to blow the exhaust gases in the right place to get the maximum increase of suction. The other challenge is dealing with the heat of the exhaust gases, which can reach temperatures of 1000°C. It’s difficult to find materials that can withstand being directly blown by gases at those temperatures.

Has the blown diffuser impacted on driving style?

Obviously the driver is modulating the engine all the time while driving the car by opening and closing the throttle, so the amount of blowing is changing, as is the amount of extra downforce generated. The time it’s changing the most is right at the apex of the corner, where the driver is starting to reapply the power, which means the drivers are having to find subtly different lines and introduce the power in a slightly different way to get the maximum benefit from the floor.