The return of the World Rally Championship after a six-month halt brought many aero issues to consider: from haybales to the rain, from punctures to the low temperatures. They all had their impact on the aerodynamics (and the performance) of the WRC cars, so we try to analyze all of them in this article, and we try to answer the question: which aero performed better in Estonia, Toyota’s or Hyundai’s?
The reliability of the aero parts was questioned at the Rally Estonia, especially on Saturday stages. Two punctures and subsequent delamination of the tire were behind the loss of a full rear fender for Rovanperä/Halttunen and Evans/Martin.
K.Rovanperä/J.Halttunen, Toyota Yaris WRC, Rally Estonia 2020, 5th – picture extracted from Dirtfishrally video
Losing a full rear fender has a significant impact on the performance of the car, as air can freely flow (which might be good in terms of not generating lift) but the advantage of forcing it to flow into the most adequate direction (rear wake) is lost. In any case, they did not lose much time with respect to their rivals, although they could have set faster times without that issue. Also, Tänak/Järveoja lost the two rear fenders before the power stage and, even so, they were able to set the second-fastest time. Does it mean that all the aero parts included in rear fenders are unuseful?
O,.Tänak/M.Järveoja, Hyundai i20 Coupé WRC, Rally Estonia 2020, 1st – picture by Tapio Lehtonen – Rallirinki
The answer is no, they are absolutely necessary. Their impact on the balance of the car is really significant. They contribute to redirecting the air from the wheel space towards the most adequate area (usually the car’s wake) to take advantage of its energy. These results only prove that the professional rally drivers are used to driving under any circumstance, so they are perfectly able to deal with an unbalanced car, even at such high velocity as those reached in Estonia. Although, if they could choose, they would always prefer a well balanced car.
Haybales were also a problem for the reliability of the aero parts in Estonia. The high number of haybales disseminated in the stages, mostly located on tight corners, combined with the quest of the second for most of the drivers, resulted in a long list of aero parts broken, with special incidence on dive planes.
O.Solberg/A.Johnston, VW Polo GTI R5, Rally Estonia 2020, 1st WRC3 – picture by Oliver Solberg Team
The relatively low temperatures in Estonia these days (15 to18ºC) allowed Toyota and Hyundai to keep partial blockage of the radiators during the stages, as shown by the arrows in the pictures below. We found no evidence of a similar blockage in the M-Sport’s Fiestas.
E.Evans/S.Martin, Toyota Yaris WRC, Rally Estonia 2020, 4th – picture by Honza Froněk – ewrc-results.com
O.Tänak/M.Järveoja, Hyundai i20 Coupé WRC, Rally Estonia 2020, 1st – picture by Honza Froněk – ewrc-results.com
E.Lappi/J.Ferm, Ford Fiesta WRC, Rally Estonia 2020, 7th – picture by Honza Froněk – ewrc-results.com
In addition to blocking plates, some drivers collected vegetals in some stages, which might have caused engine overheating in case they were not removed at the end of the stage.
C.Breen/P.Nagle, Hyundai i20 Coupé WRC, Rally Estonia 2020, 2nd – picture by Hyundai Motorsport
The duo Rovanperä/Halttunen was penalized by removing the radiator blocking plates in a control area (not allowed by regulations). The penalty was 1 minute, but for sure the damage would have been worse if they had done the stage with the blocking plates installed, as we saw with the last Rallye Monte Carlo, where all three Fiesta WRC cars suffered from overheating caused by leaves.
K.Rovanperä/J.Halttunen, Toyota Yaris WRC, Rally Estonia 2020, 5th – picture by Tapio Lehtonen – Rallirinki
The rain during Saturday night and early hours of Sunday contributed to the appearance of mud in some roads, especially in the shadowed corners. To prevent mud accumulation inside the rear fender vents (which means losing efficiency as well as gaining extra weight), Toyota introduced different solutions in their cars. Rovanperä/Halttunen and Evans/Martin left the service park with some internal blocking plates, as shown in the picture below, where the hook of these plates is visible between the rear fender vanes.
K.Rovanperä/J.Halttunen, Toyota Yaris WRC, Rally Estonia 2020, 5th – pictuure extracted from wrcplus.com video
These plates are normally used in the service park, to protect the vanes from the operations inside the car carried out by the mechanics.
Toyota Yaris WRC rear fender vents blocking plates
K.Meeke/S.Marshall, Toyota Yaris WRC, Rally Catalunya 2019, at the service park
To get the same effect, the rear fender vents of the Ogier/Ingrassia car had en external blockage of the lower vanes.
S.Ogier/J.Ingrassia, Toyota Yaris WRC, Rally Estonia 2020, 3rd – picture extracted from wrcplus.com video
The reason behind the use of these solutions is the design of the internal vanes. Toyota’s vane (concave) shape allows mud to accumulate, as shown in the image below from Rovanperä/Halttunen car.
Other teams have not this problem, due to a different vane design. Hyundai introduced in Estonia, for the first time in the Championship, the new design of the rear fender vents, with the vanes in a vertical position. First seen in June tests in Finland, this configuration has been used since then in all tests and rallies where the Alzenau-based has taken part, and now in the WR Championship. Note that rear fender vents modification does not require a joker, as it can be done just as a variant option (VO), so there is no need for homologation.
T.Neuville/N.Gilsoul, Hyundai i20 Coupé WRC, Rally Estonia 2020, retired – picture by Hyundai Motorsport
These two solutions were used only during the first Sunday morning loop of stages. Once the roads were dry, they were not required and they removed by the teams… which also proves the beneficial effect of the rear fender vents previously discussed.
S.Ogier/J.Ingrassia, Toyota Yaris WRC, Rally Estonia 2020, 3rd – picture by Toyota Gazoo Racing WRT
Surprisingly, Toyota did not use their usual solution for muddy and/or snowy stages, which consists of a reduced vanes vent, as they did in Sweden this year.
S.Ogier/J.Ingrassia, Toyota Yaris WRC, Rally Sweden 2020, 4th, picture by Toyota Gazoo Racing WRT
Which aero performed better in Estonia, Toyota’s or Hyundai’s?
The supposed similarity between Rally Estonia and Rally Finland stages (which proved not to be so similar at the end), the excellent results obtained by Toyota in Finland in the last three years and the better starting position of the Hyundai cars generated some controversy on who was going to be the best performer in Estonia. The question is relevant for us, as such fast stages require an optimal aero package. So, who performed better will tell us which aero was better for the Estonians stages.
We will try to answer based on the stage results, which are listed in the table below, ordered by average speed.
The first conclusion is that, in most of the stages, the same car set the fastest time at the first and second pass, which proves that results are consistent.
The second important point is that Toyota set the fastest time in the two fastest stages (SS12/15 and SS2/7), in some medium speed stages (SS14/SS17) and in the slowest one (SS13/16). Similarly, Hyundai set the fastest time in some very fast stages (SS3/8 ) as well as in medium speed stages (SS4/SS9). Such equality seems to confirm that no team seems to be specialized any more in fast or medium-fast stages. On the contrary, the efficiency of the Hyundai’s latest aero package seems to have equaled the efficiency of the Toyota, and now they both fight for the fastest time no matter what is the average speed of the stage.
So, the answer is, in our opinion, that both cars showed similar aero performance, most probably thanks to the latest development implemented by Hyundai. Such equality is good in terms of the show… except that such a high level of efficiency prevents M-Sport from being competitive. A pity that they did not introduce in Estonia the new front aero package tested in Greystoke in the last months. But, as Malcolm Wilson declared to DirtFish.com before the event, they will not be using it at least until Sardinia, as there is still some stock of old pieces available. Which makes a lot of sense, in such a weird season. Hopefully, it will contribute to improving their performance for the next one, the last season with the current WRC cars.