Kevin Abbring on the aero of RX and WRC cars

The celebration of the opening event of the FIA World RX Championship in Barcelona last weekend represented for WRCWings a nice opportunity to get back in touch with top-level rallycross discipline. As we reviewed in previous articles, aerodynamics also plays an important role in rallycross. But to what extent? What are the main differences (aerowise) with WRC cars? To answer all these and other questions, we contacted one of the most rally-experienced RX drivers, Kevin Abbring, who very gently accessed to answer our questions while giving his point of view on the aero of both disciplines. And this is a summary of what he explained to us.

K.Abbring, UNKORRUPTED Renault Mégane RS, 2021 Catalunya RX

The first question is obvious: Kevin, what it is your impression about the aero of the RX cars?

My first experience with an RX car in the competition was in 2019 with a Škoda Fabia (aligned by ES Motorsport). The first comparison that I can make is between the Škoda and the Mégane RS I’m driving now, and there is a huge difference in the fast sections, especially in the fast sections combined with some angle. There, with the Mégane, you feel that the rear is really stuck into the ground, which is what you want. On the other hand, even if it’s really fast, you always want your car to rotate, and the Megane has a really good balance between the right amount of aero and stability.

The Škoda looked impressive from the outside in terms of aero, with a big rear wing quite similar to the others, but there were so many things that were different from the Mégane. It’s a matter of, even if you do an aerodynamic model, you know how much testing and prototypes actually need to be made to verify all these aspects. It is a huge part in terms of development cost and so on. With the Mégane, I think we’ve quite optimized that.

What aero features of the Mégane would you highlight?

The real wing, especially. It has a good balance between high-speed stability and full speed, especially for tracks like Canada (used in the past) there are high-speed sections and you really want to achieve high speed but you don’t wanna lose out on stability in the fast.

In addition, it has the side fenders in carbon (inside the yellow circle in the picture above) which really influences the way the car behaves under the angle and the braking. Apart from it, especially here in Barcelona (Catalunya RX circuit) in corner 8 (the long corner before the second portion of gravel) it really helps to carry quite a lot of speed and then braking without losing the car. On the other hand, the car feels really stable there and it is hard to get the right rotation, but this is also due to the inertia of the car. It is a bit bigger, which has advantages in some places and you have to deal with it on other places.

2021 Catalunya RX

In the RX you have often to drive behind other cars, does it have a big impact on the aero performance of the car?

Being behind other people here has a bit of an influence, but in the end, if the guy in front of you brakes, you have to brake as well, so you reduce speed quite quickly, and on these cars, with these tyres, it is incredible how much speed you can reduce in a certain amount of time.

What about the rear cooling (something that we will also see in the 2022 WRC cars), how does it affect the aero behaviour?

The airflow coming into the engine obviously has an impact on the aero. As we ask so much from the engine even for a short time, you really need to have your engine cooling right, we have the coolers in the back, which means that we have those big shapes into the rear arches made to optimise the engine cooling. It obviously doesn’t help aero, so the shape is made in a way that it has quite an efficient balance in between both.

 

K.Abbring, UNKORRUPTED Renault Mégane RS, 2021 Catalunya RX

Locating the coolers at the rear surely affects the mass distribution, how does it impact you as a driver?

The more balanced the car is, the better. It has a reason, the engine is put on a position that you potentially would have the space in front (for the radiators), but it is a contact sport, therefore it is a bit risky to have the coolers in front if you have some incidents on. But it definitely helps the way the weight is distributed in the car. In the end, this is an add to the balance of the car, combined with the brakes, the position of the engine and the driver. It is a complete package calculation made with all the aspects you have to implement in the car.

Renault Mégane RS wind tunnel test at MIRA facilities, 2018

The Mégane RS was one of the most developed cars in the RX, in terms of aero, thanks to the work developed by Prodrive. But the design of the aero parts is fixed and cannot be changed during the season. How can you then modify the aero balance of the car?

In terms of the aero balance between the front and rear of the car, the main thing is by changing the rake, the pitch of the car, which has quite a bit of influence. We are not allowed to have different shapes of bumpers, etc. As long as you carry the speed underneath the front bumper, which makes quite a difference, there are not many other things that influence, just the rake.

You drove for Hyundai in the WRC in 2015 and 2016. How does it compare to the aero of a WRC car?

In comparison with a current WRC car, an RX car has almost no aero, but the influence is less important because, although here you achieve high speed really quickly, the distances are quite short, so, it is not super pronounced, it just makes a small difference,  it’s not that it changes the car completely. But, if you would put the RX car on a rally stage, for sure you would notice the differences a little bit more because you travel at high speeds in a rally for a longer time.

K.Abbring/S.Marshall, Hyundai i20 WRC, 2016 Rally Catalunya, 7th

Any other differences between RX and WRC?

The driving style. In WRC these days they have a lot of aero, more than ever, and you see that even on gravel now, the driving style is quite similar to the tarmac, in the sense that there’s not much angle put on the car. Because, if you go over 10 to 15 degrees of angle, you lose a lot of aero. In RX, in a way, it’s likely the same, but the effect is less because our tyre needs some slip; if we drive too clean without enough angle, we don’t get performance from the tyres. This is quite an interesting difference because it’s a driving style which has to suit, even though it is better or worse for the aero, but in the end, the tyre is the tyre, they need a certain amount of angle. On the WRC cars, the tyres are different, the tyres we drive here are really specific. If you slide, you don’t lose the grip completely (both in tarmac and gravel) cause, otherwise, people would end up against the wall all the time.

K.Abbring, UNKORRUPTED Renault Mégane RS, 2021 Catalunya RX

When you have combined loads in the corner, if you want to apply the throttle you need to calm down the car again, because obviously, the car works best if it is pointed into the straight line. Tyres are made to go straight, not to go on corners, otherwise, it would be a boring sport.

With the amount of aero that we have, we would love to had a similar driving style of WRC these days, even if they have a bit more aero, but we would not be fast because we would not get the maximum from the tyres.

Thank you Kevin for your very interesting comments, and all the best for the 2021 season!

K.Abbring, UNKORRUPTED Renault Mégane RS, 2021 Catalunya RX

 

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