What’s the deal with the new modifications in the Hyundai i20 Coupé WRC 2021?

The season 2021 is about to start and, as usual, the teams have been working on some aero modifications to improve their cars’s performance. While Toyota and M-Sport will start the season with the same aero package seen in the last event of last season, the big news comes from Hyundai. After completely modifying the aero of the i20 Coupé WRC during 2020, still some changes arrive for 2021. And, on top of them, the use of serrated dive planes has attracted the attention of the rally community, since its first appearance in the car of Tänak/Järveoja in the Estonian Kehala Rally, back in November 2020. What is their purpose, as well as of the other modifications, is what we will try to explain in the following lines, together with the other modifications implemented from Alzenau.

Front detail of the Hyundai i20 Coupé WRC evolution version 2021 – picture by Hyundai Motorsport

The picture above shows in detail what is a serrated dive plane: the external part of the upper plane has been modified, with three slots. What for?

To explain it, we need first to review the purpose of a dive plane*, which is double:

– on one side, to generate downforce thanks to the impact of the airflow (white arrows in the image below) over them that is transformed into vertical pressure (downforce, represented by yellow arrows), which is applied onto the front wheels, increasing the grip at the front axle.

O.Tänak/M.Järveoja, Hyundai i20 Coupé WRC, ACI Rally Monza 2020, 2nd – picture by ACI Rally Monza

– Secondly, part of the air exiting by the edge of any dive plane generates a row of swirls or vortices (white arrows in the image below) that travels down the sides of the car and act as a barrier, to prevent air from entering under the car by any of the sides (same as skirts do). Without them, the air flowing on both sides of the car could enter under the car with the result of a pressure increase. With them, the pressure under the car remains low, so more downforce is generated (by the pressure difference between the top and below the car). In this case, the benefit is obtained across the whole car, as the barrier effect allows air to flow faster from the front splitter to the rear diffuser, thus grip will increase in both axles.

O.Tänak/M.Järveoja, Hyundai i20 Coupé WRC, ACI Rally Monza 2020, 2nd – picture by ACI Rally Monza

The addition of the slots in the edge of the upper dive plane converts it into a multiple dive plane. In our opinion, the result is that each small slot generates a row of swirls, thus generating a bigger and more effective barrier on the side of the car. Less air is allowed to enter under the car, and the pressure there remains even lower. Thus, the addition of a serrated dive plane would result in an even higher downforce generation under the entire car (not only at the front).

O.Tänak/M.Järveoja, Hyundai i20 Coupé WRC, 2021 pre-season test, France, December 2020 – picture by Julien Prioux for Planetemarcus

The second modification introduced by Hyundai is the addition of an endplate in the lower dive plane. The goal is to avoid that the (high pressure) air flowing over the plane mixes with the (low pressure) air flowing under the plane, thus increasing the efficiency of the plane in generating pressure at the front of the car, that is, again higher downforce at the car front.

Also, the endplate better directs the airflow onto the front fender and the winglet on top of it, where additional load is generated.

The third modification consists of the addition of a small vertical plate (known as Gurney flap) at the rear of the winglet (noted with an a in the picture below) and the upper surface of the front fender (b) of the Hyundai i20 Coupé WRC.

Detail of the front fender of the Hyundai i20 Coupé WRC 2021 – picture by Hyundai Motorsport

The presence of these small vertical plates forces the air (white arrows) to flow upwards, and (because of the action-reaction principle) the result is that pressure (yellow arrows) increases over the wing and the fender.

Airflow over the front fender winglet: 2020 version (above, picture by Julian Porter) and 2021 (below, picture by Hyundai Motorsport)

Also, the flaps reduce the airflow speed, which means even higher pressure over these elements. Both effects combined contribute then to increase downforce over the front axle.

In summary, by implementing all these modifications, the Hyundai i20 Coupé WRC is able to generate higher downforce not only at the front of the car (where it is more necessary, to improve the car balance) but also on the entire car, allowing even higher speeds at the corners thanks to the improved grip.

Toyota also evaluated some modifications at the front of the car in the Pirelli December tests, to increase the downforce generation at the front of the Yaris WRC, as we reviewed in a previous post. These modifications were not included in the car used in January tests, which probably means they will not be implemented for the Rallye Monte-Carlo, but maybe we will see them again in new tests or in future events if they are finally homologated.

O.Tänak/M.Järveoja, Hyundai i20 Coupé WRC, 2021 pre-season test, France, December 2020 – picture by Julien Prioux for Planetemarcus

*Dive planes (also known as dive plates or canards or flicks) are the small planes located on both sides of the front bumper, usually in pairs, as shown in the picture above.

This post includes the opinions of the author, which are certainly not always right. If you detect any error or you disagree, do not hesitate to contact us, by sending an email to wrcwings@gmail.com. We love to learn!

 

 

 

 

 

 

8 thoughts on “What’s the deal with the new modifications in the Hyundai i20 Coupé WRC 2021?

  • 2021-01-18 at 17:08
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    As always very informative and insightful. We rely on you !!.

    Reply
    • 2021-01-18 at 17:45
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      It’s a big responsibility…but I accept it. Thanks!!!

      Reply
  • 2021-01-19 at 02:32
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    Wow! I finally found a way to access your website after some time. It appears my country’s ISP somehow can’t connect to this place with normal means, so here I am! Belatedly!

    Regardless, I’d also like to suggest an addition to your analysis. In other high-downforce motorsports, staggered serration on air-facing surfaces mainly serves to generate vortices under high angle of attack, and not primarily to aim them to seal the floor. If you pay attention to how F1 & MotoGP front wings evolve and change the way the machines needs to be driven, lesser planes/serration actually generates stronger vortices as speed increases, but are less stable as speed drops (braking-turning rotation phase). Is this different in WRC owing to their nature?

    Reply
    • 2021-01-20 at 21:06
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      Hi Kevin, welcome back! And thank you for your comment. As I see it, the difference with a F1 car (I’m less aware of MotoGP) is that (in a F1) the flow past the front wing has a big impact on the aero of the rest of the car, due to its location and width. In a WRC car, the impact of the dive planes can only be used on the car sides, hardly in the body (due to its geometry). So, the advantage of the vortex generation can only be used in very few locations, such as the mentioned sealing effect, although they might possibly have more. We should see the CFD results to confirm.

      Reply
  • 2021-01-21 at 12:04
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    Hello again ! Talking about the rear wing today. Ford and Toyota have a very long and wide lower rear wing plate (Hyundai’s one is seemingly smaller). Basically they cover everything that stays below the upper part of the rear window. Why they have made that so massive and what advantages/disadvantages it has and does it increase also the car’s drag.

    Reply
    • 2021-01-21 at 21:44
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      Hi Laur, welcome back! The lower plate needs to be as big as possible to generate pressure thanks to the air flowing under the upper wing. By regulation, they have to be attached to the rear window, so there is no chance for air to flow under it. For sure they generate some drag, but the downforce largely compensates it.

      Reply
  • 2021-01-21 at 18:42
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    Hello again! Got a question from the other side of the WRC car. The rear wing.
    1. The rear wing lower plate is really massive. (especially for Toyota and Ford) It covers basically the entire rear window below the top of the window. What are the principles behind that? Low pressure under the rear wing and high pressure on top of the plate to generate downforce? Does it also increase drag as the rear of the car has basically a vacuum (especially at high speeds) because the rear end is really boxy (with wide and high wheel arches)
    2. On gravel events, the wake (with dust) behind the car looks pretty unique. How the air is directed over the rear wing that this kind of wake is made.

    Sincerely, Laur

    Reply
    • 2021-01-21 at 21:50
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      The rear wake of the WRC cars has three different areas: a fast area on top, with it coming from the rear wing, a quieter medium area on the center, and again a fast area coming from rear diffuser. The slower the flow in the center area, the more drag the wake generates, so you need to remove air from there as quick as possible. Here is where the air coming from rear fenders can help to reduce drag. You can see it more graphically in this post: https://www.wrcwings.tech/2020/03/29/removing-brakes-cooling-airflow-from-wrc-cars/

      Reply

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