Cars

<em>Photo: Richard Pardon</em>

The aerodynamics of the SF90 Stradale

Managing airflow around a car is crucial to performance. None more so than for the SF90 Stradale, Maranello's first hybrid. We get a guided tour of the innovations that led to two patents for Ferrari
Words

Richard Bremner

The air through which ultra-high performance cars like the Ferrari SF90 Stradale travel is both a friend and an enemy. It is a vital friend to the 780cv twin turbo V8 of course, which needs air to breathe and to burn the fuel that generates propulsion. The V8’s support systems also depend on the atmosphere, the rapid passage of air being needed to chill its radiators and intercoolers. The brakes are also vitally reliant on air to disperse the furious heat caused by slowing, and the car’s bodywork must be precisely sculpted in order to harness the scything displacement of air and its partner effect, gravity, the pairing that glues it to the road below.

But air is also the enemy of performance. It creates wind resistance, noise, and, on occasion, the potential to mildly destabilise the car in a crosswind, for example, and under braking. Controlling the invisible passage of air over and through a car is, therefore, a central mission in the creation of any modern supercar.

The wheel spokes extract air from the housings, helping to keep the car's nose down <em>Rendering: Arscolor Media Production</em>
The wheel spokes extract air from the housings, helping to keep the car's nose down Rendering: Arscolor Media Production

To visualise the passage of air under, over, around and into an SF90 it’s helpful to think of the car as a fast-moving aquatic creature. Picturing water passing around and through its vents, ducts and vortex-generators makes it easier to imagine the task facing Aerodynamics Manager Matteo Biancalana and his team. To try to give an idea of this complexity he uses a diagram showing the passage of individual bundles of snake-like air streams, each colour-coded according to their direction and role.

“There’s no interaction between these airflows,” says Biancalana when describing the impressive achievement of marshalling the air, something only part-produced by the computational fluid dynamics (CFD) process; the wind tunnel and experience play their part, too. CFD has produced an active upper body aero aid for the first time on a series production Ferrari, its deployment both amplifying and reducing certain characteristics. Among them, the downforce and the minimising of braking distances through increased drag. “But it also needs a 25 kilometre range as an EV, so we’re also trying to reduce drag,” explains Biancalana.

Air creates drag, but can be harnessed both to cool and to pin the car to the road <em>Rendering: Arscolor Media Production</em>
Air creates drag, but can be harnessed both to cool and to pin the car to the road Rendering: Arscolor Media Production

“We set up the rear of the car to have the lowest drag possible, using a feature from the 488 GTE- based P80/C, a one-off track car, that we used as a laboratory.” The car’s rear wing is two-piece: it has a fixed element and a movable fairing. In the low-drag condition the two pieces are aligned and the air flows beneath. When cornering or braking at speed the forward part lowers and closes the gap. “It’s a patented solution,” says Biancalana.
A CFD image of the SF90’s underside at speed reveals a delta-shaped area of high pressure up front that sucks the car to the ground. Its effect is hugely increased when the rear fairing has descended for maximum downforce, producing a “mutual interaction between the two systems. The car is then well-balanced from front to rear,” Biancalana explains.

Managing air flow is crucial to other parts of the car, like the wheels and their housing. Wheels generate turbulence, whilst at speed the wheel arches fill with undesirable, lift-inducing high-pressure air. “We’ve created a turbine effect with the spokes,” the aerodynamics manager explains. This patented system evacuates air from the wheel arches while encouraging it to travel very close to the car’s flanks, reducing drag.
The result is a very complete and ingenious aerodynamic package that Biancalana says has been “the most challenging yet for a Ferrari series production car”.

 

Ferrari