Graphical review of aero devices included in the upgraded FIA Rally1 regulations

The upgraded version of the Specific Regulations for Rally1 cars (APPENDIX J – ARTICLE 262 – 2022) approved by the World Motor Sport Council last week (October 19th) and published today (October 27th) includes, amongst other small changes, the definition of the different aero devices usually included in Rally1 cars, but with some exceptions. These definitions have been included in article 038 of the new version of the regulations. To better understand what part refers to each definition, this is our graphical presentation of the different parts, as well as the purpose of each part.

1. Aerodynamic Profile – replaces wing profile in the previous version
Defined as a section generated by two arcs with different curves and/or centres joining a leading edge at the front to a trailing edge at the rear, the purpose being to exert an aerodynamic effect, lift or downforce.

Aerodynamic profiles are usually hidden behind endplates, so the best way to see them is when a car losses one of the endplates, such as in the images below.

Toyota GR Yaris Rally1 rear wing aerodynamic profile – image extracted from WRC All Live images

Note that the shape of the wing profile is the same as the profile of an inverted airfoil, as it is designed to generate downforce, instead of lift.

Another aerodynamic profile can be seen in the support of the Toyota and MSport’s Rally1 car broken wing mirrors.

Toyota GR Yaris Rally1 wing mirror aerodynamic profile

There exist hundreds of aerodynamic profiles. One of the best compilations of wing profiles used in racecar competition is included in the excellent book Wings, by Enrico Benzing (more info here).

2. Winglet
Winglets are low-span (low-width) aerodynamic-profile, with or without any endplates. Their cross-section is normally airfoil (aero profile) shaped with a leading edge and a trailing edge.

The best examples of winglets can be seen on both sides of the rear wing of the Hyundai i20N Rally1 and the Ford Puma Rally1.

Low span wings (winglets) on the sides of the rear wings of the Hyundai i20N Rally1 (left) and Ford Puma Rally1 (right)

3. Dive Plane
Defined as a continuous surface that protrudes beyond the bodywork surface and whose function is to create additional downforce and channel airflow (dividing the airflow channeled between an upper and lower surface).

Designed to generate downforce, they are also used, at the front of the car, to generate a row of swirls (vortices) that travels alongside the car, acting as a barrier to prevent air from entering under the car. The result is that pressure under the car remains low, ensuring that the car remains stuck to the ground, thus increasing grip. A more detailed explanation can be found in this article.

Dive planes in 2018 WRC cars. From top to bottom: Hyundai i20 Coupé WRC, Toyota Yaris WRC, Ford Fiesta WRC and Citroën C3 WRC – images 1 and 2 by Nacho Mateo (, 3 by @world and 4 by Honza Frônek

Surprisingly, dive planes are included in the definition of a regulation that, at the same time, forbids them. They were one of the most distinguishing features of the previous generation of WR cars.

4. Wing Fence
Defined as flat plates fixed to one or several surfaces and parallel to the airflow.

They are usually located on top of the upper wing, in order to channel air over the wing, while also taking advantage of crossflow during cornering. They were very common in the past, in the rear wing of iconic rally cars such as the Peugeot 206 WRC Evo2, Subaru Impreza WRC03 or the Ford Focus WRC03. The only Rally1 car using them is the Toyota GR Yaris Rally1, as shown in the image below.

Toyota GR Yaris Rally1 rear wing fences

Note that, while in the Toyota Yaris WRC the fences were part of the swan-neck supports, in the GR Yaris Rally1 these supports are not connected to the base of the wing, while are floating, as shown in the image above.

5. Gurney Flap
Defined as a Strip installed along the edge of a surface.

The goal is to force air to flow over them, causing a delay in separation and increasing downforce generation. A more detailed explanation can be found in this article.

Ford Puma Rally1 (top) and Hyundai i20N Rally1 (bottom) rear wings with Gurney flap

6. Bargeboard/Turning Vanes
Curved planes, situated longitudinally whose function is to guide and redirect the airflow.

In the case of Rally1 cars, the most similar to a turning vane is the front fender cover, which fosters air to flow over them to generate some downforce, and to travel alongside the car towards the side scoop and the rear wing’s winglets.

K.Rovanperä/J.Halttunen, Toyota GR Yaris Rally1, 2022 Rally Catalunya pre-event test

Other aero-related modifications included in the upgraded version of the regulations of the Rally1 car published today include the possibility of adding openings on the windscreen and on the rear window for cooling purposes. These modifications are joker-free, as they will only require a Variant Option to be homologated.

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2 thoughts on “Graphical review of aero devices included in the upgraded FIA Rally1 regulations

    • 2022-10-28 at 15:19

      Thanks much for your kind words, and for the excellent link, a must!


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