Aero upgrades give Hyundai a fighting chance in Finland

After a dismal performance on Rally Monte-Carlo, Hyundai is chasing a return to form on the second round of the World Rally Championship – Arctic Rally Finland. However, if the Korean manufacturer was to pick an event to bounce back on, high-speed Finnish stages would be at the bottom of the list.

Hyundai is yet to score a podium finish in Finland since the team’s WRC return in 2014. Meanwhile, title rivals Toyota has it mastered, taking three Rally Finland wins from three since 2017.

After all, the Toyota Yaris WRC was born and bred in the Finnish forests.

Considering all this, there is one trick up Hyundai’s sleeve that gives its drivers a fighting chance of breaking Toyota’s reign on Finnish soil.

Aerodynamics.

Hyundai revealed several upgrades to the i20 WRC’s aerodynamic package in 2020. A new rear wing complemented with an updated diffuser, modified rear arch vents, and an additional winglet above the front arches.

The result?

A Hyundai 1-2 on Rally Estonia last September, a high-speed gravel event many expected Toyota to adapt best to.

Here is Rally Insight’s take on how Hyundai’s aerodynamic improvements have helped close the gap to Toyota.

Rear wing

Hyundai introduced its new rear wing for Rally Mexico last year. Mechanical woes ruined the team’s chances early on in the event but Ott Tanak and Craig Breen made amends next time out in Estonia.

As the image comparison (between 2019 and ’20 cars) above shows, Hyundai’s rear wing now features two endplates between the upper and lower pieces of the wing. The endplates extend down the rear windscreen, cutting off any airflow from the i20’s side windows.

This creates an area of low pressure directly beneath the rear wing. Combined with the high pressure above the wing, where the airflow is moving much faster, the pressure difference creates downforce across the rear axle and therefore produces more rear-end grip.

Hyundai’s latest rear wing design is more in-line with what Toyota has exhibited since its first Yaris WRC in 2017.

The endplates also help to keep airflow from the roof and side windows separate. This allows the wing profiles to use the airflow more effectively, creating more downforce.

Endplates also reduce the mixing of low-pressure airflow beneath the wing with high-pressure airflow above the wing. This again increases downforce.

This was Hyundai’s first significant change in rear wing design since its latest generation of World Rally Car was introduced in 2017. Design analysis and test feedback from drivers will have helped introduce a package that improves high-speed grip and stability.

Diffuser

Hyundai introduced rounded outer corners on its diffuser at the start of 2020. Previously the diffuser just had square corners.

The refined design will improve the efficiency of airflow through the diffuser. The airflow is more likely to stay in contact with the diffuser’s rounded corners. This reduces airflow separation and drag.

The depth of the diffuser also looks different following Hyundai’s update. Engineers and designers will have used simulation methods and test results to optimise the diffuser’s geometry, including the angle at which it slopes upwards towards its exit.

An optimised diffuser angle is crucial as downforce increases with steeper angles but if the angle is too steep then flow separation can create drag.

Aerodynamic design is always about striking a balance between generating downforce, and more grip, without creating drag, which slows the car down at high speed.

Rear arch vents

Another interesting design change was added to Hyundai’s aerodynamic package before Rally Estonia last year. The louvres behind the i20’s rear arches were switched from the regular horizontal pattern to a vertical pattern.

In general, the louvres are designed to control the airflow exiting the wheel arches. It is vital to encourage airflow out of the wheel arches. Otherwise, there would be an area of high pressure in the wheel arch which would negate downforce generated at the rear of the car.

Hyundai’s vertical louvres will push this airflow away from the rear of the car. Photos show how the louvres are angled to the side of the car.

This is to keep the turbulent airflow away from the car’s wake which is an area of low pressure behind the car. This area of low pressure resists the car’s forward motion and reduces the car’s potential top speeds.

The diffuser and rear wing profiles contribute to this area of turbulent air so redirecting rear arch airflows away from the car’s wake could reduce its overall drag. This would improve Hyundai’s high-speed performance.

Front arch winglet

Hyundai introduced a winglet above the i20’s front wheel arches for Rally Mexico last year. The update came at the same time as its new rear wing.

The winglet produces front-end downforce which will improve turn-in grip and reduce understeer during cornering. The additional downforce generated by Hyundai’s significant rear wing upgrade could have required more front-end downforce to maintain a similar front-rear grip balance.

Another area designers will have considered is how the winglet directs airflow towards the rear of the i20. While the winglet creates downforce it also creates an area of turbulent, inefficient airflow behind.

Hyundai engineers will have positioned and angled the winglet in a way that doesn’t negatively affect the airflow entering further aerodynamic features towards the rear of the i20.

Enough to beat Toyota in Finland?

Coronavirus meant Hyundai didn’t get a chance to prove if these changes improved their performance on Rally Finland last year. However, a 1-2 on Rally Estonia’s high-speed gravel stages certainly showed a new turn of pace for Hyundai.

That result can be taken with a pinch of salt as Tanak’s home knowledge would certainly have helped with defining an optimal i20 set-up in Estonia. Also, while Toyota struggled for the first half of that event the Japanese manufacturer picked up every stage-win on the event’s final day.

Toyota aced its aerodynamic design from the get-go in 2017. And when you look at Hyundai’s 2020 updates they largely bring the i20 closer in-line with the Yaris WRC.

Neat concepts like the vertically orientated rear arch louvres are unique, however, and the changes should certainly bring Andrea Adamo’s crews closer to the once untouchable Toyota built for Finnish terrain.

N.B. These are my interpretations of Hyundai’s latest aerodynamic features. While I tried my best to represent the design concepts and aerodynamic principles accurately, it doesn’t guarantee that I am 100% correct. Aerodynamic features are designed to work together as a package and Hyundai engineers will have utilised computer simulators, test data, and driver feedback to come to the best decisions when redesigning the i20 WRC’s aerodynamics.