On Thursday of the Austrian Grand Prix, Mercedes ended up in the crosshairs. The issue concerned the diffuser of the W17, which was ultimately deemed non-compliant by the International Federation. For this reason, the German car showed up in Spielberg with a modification to the upper part of the diffuser.
The International Federation’s Regulations
The FIA, in regulating the 2026 single-seaters, has maintained dimensional boxes. Within these control areas, the limits and shapes of the various elements are defined. This type of constraint applies to both the aerodynamic package and the mechanical components.
However, we can often observe different technical solutions on the cars in terms of packaging. The reason is simple: certain elements are relocated to fit within the regulatory box. Let’s look at two examples to better understand this.
The first concerns the rear suspension pickup point on the Aston Martin. During the Bahrain tests, it seemed that the rear leg of the upper wishbone was anchored directly to the wing pillar on the AMR25, a concept that Newey had already utilized during his time at Red Bull.
Instead, upon closer inspection of the solution, Newey deliberately extended the crash structure located behind the gearbox upwards, providing a solid base for the suspension: the two wing pillars are incorporated into the structure itself.
The other case is that of Ferrari, which led to the creation of the FTM exhaust. The flaps that take shape around the crash structure are diverse and all designed to manage the exiting exhaust gases. The goal? To increase rear downforce through exhaust blowing on the wing.
This solution stems from a precise study by the Maranello engineers regarding the regulatory constraints and involves a specific choice during the design phase. We are referring to the position of the differential, purposefully moved rearward to fit within the regulatory box governing that area of the car, thereby allowing for the insertion of a larger number of flaps.
The Ferrari study that knocks out Mercedes
Precisely because Ferrari studied this area of the car in such depth, the engineers led by Loic Serra quickly realized that the solution on the W17’s diffuser, introduced in Canada, was in fact illegal. Let’s take a step back: Mercedes could not use the Ferrari solution between the exhaust ramp and its exit.
That is why they tried to condition the airflow at the rear with fine-tuning: we are talking about the three bulges with a serrated trailing edge (also in this case clearly inspired by Red Bull), which are useful for creating additional vortices, accelerating the airflow, and recreating a larger volume to generate more downforce.
To create these bulges, the German team had engineered a support structure in a forward position, without merging them directly onto the diffuser, in order to comply with the regulatory box. A loophole that the FIA had deemed legal until Ferrari’s intervention.
The clarification letter from the Maranello manufacturer, therefore, brought down the Mercedes solution which, as we can observe in the following technical illustration, in addition to removing the three bulges, has changed the pointed shape of the trailing edge, replacing it with two rectangular teeth.
Apparently, keeping in mind the performance of the German cars at the Austrian Grand Prix, the new version of the diffuser’s trailing edge works and allows the W17 to generate the required amount of downforce at the rear of the car. Basically, much ado about nothing.
