Shape and performance of the Mercedes-AMG ONE
The Aerodynamics of the AMG ONE are not just elegant in design, they are elegant in their function. Every detail, curve, and surface of the outward appearance of this excellent machine is geared to achieve the highest performance possible.
What comprises the look of the AMG ONE is much more than just simple aesthetics. In our interview, Dr. of Engineering and Technical Lead of Aerodynamics, Gustavo Estrada, tells us about how ‘form follows performance’ in the AMG ONE.
The Aerodynamics of the AMG ONE are not just elegant in design, they are elegant in their function. Air is directed and moved around its form like a maestro directing a superb orchestra. An optimum of balance is required between drag, downforce and air massflow for cooling requirements to achieve the utmost this vehicle is capable of.
Could you tell us about the process of development of the aerodynamic features and modes on the AMG ONE? Which different modes are available on the vehicle?
Our Mercedes-AMG team has the know-how and the access to equipment like wind tunnels, computer simulations (CFD) and drive simulators for the development of such a vehicle in order to achieve the maximum possible efficiency.
This development process started at a very early point, way back before we presented the car at the IAA 2017 in Geneva. The coordination between aerodynamic, packaging, design and the definition of the proper technologies are the basics at an early point in development. We started generating a lot of interesting ideas to achieve the ambitious goals that we set for ourselves, and always with street legal certification in mind. We had to keep that in focus during the development of the vehicle’s shape and its aerodynamic features in order to fulfill these requirements.
Not only was “form follows function”, but “form follows performance” one of the main tasks to be accomplished together with the design department. The result is a shape that expresses this “performance personality” that we have achieved: each part of the vehicle interacts not only in an elegant way, but also shows, to the experienced eye, functionalities that generate aerodynamic performance.
From an aerodynamic point of view, it is almost impossible to lay focus on only one feature; we view the car as a whole. In the aerodynamic development of a vehicle, two meters in front of the car and three or four meters behind the car are included due to the air interaction with the object. This flow washes over not only the visible surface, but through the cooling ducts, underbody, hotspots, and engine compartment.
Any modification at the front will have an impact on the rear, and the other way around as well. The active aerodynamic features are developed specifically to maximize, minimize, or to correct some flow phenomena, to produce the needed forces applied to the car to achieve the maximum performance.
Now I can begin to answer this question regarding the three defined drive modes: “High Way” as street-legal, “Race Max Downforce” for maximal driving dynamics, and last but not least, “Race DRS” for a high downforce level with a reduced drag coefficient for reaching top speeds. From an aerodynamic point of view, we needed to develop not only one, but three cars in one! This was the same situation with our AMG GT Black Series (WLTP: Kraftstoffverbrauch kombiniert: 12,8 l/100 km | CO2-Emissionen kombiniert: 292 g/km | Emissionsangabe ), but at an even higher level.
These different driving requirements were the impetus for us to develop the various active aerodynamic features for this vehicle.
As an example, the vehicle body has fender louvres outlets that increase downforce massively on the front axle when they open, as well as the rear wing concept. The rear wing’s camber in stowed position wasn't enough to get the maximum efficiency that we wanted to achieve, so we developed an extra active extension that increases the load and the rear downforce with it. These active devices are also present on the underbody. They are very small, lightweight, compact but with a huge amount of influence on this area, especially the front diffuser.
What amount of downforce is possible with the AMG ONE and at which speeds?
We are not allowed yet to comment regarding the amount of downforce we have reached with this car, but we have fulfilled our own requirements. What I can tell you is that we set targets at the beginning of the development process and we have even increased those targets. We learned that, with the power of this engine plus the electric motors in interaction with torque vectoring, we could increase the downforce targets that we had already met for better driving dynamics. The wind tunnel and CFD results, in combination with the feedback from the drive simulator and the track, pushed us to go even above the limits we had defined. From an engineering point of view, that's great, that's a dream, because we always want more and we don't like limits.
We needed to achieve the right amount of aerodynamic load and get the right ratio between the front and rear axles: the so call aerodynamic balance. The ratio of this downforce on the front and the rear axle must be modified when driving in the three different modes because of the diverse requirements.
Can the different modes, highway traffic, maximum downforce and track DRS be combined?
Each driving configuration of the vehicle requires a specific aerodynamic balance. Each of the features interact with the object to produce the balance that is required. We are not able to combine the three different modes, it would be a mistake to try to do that because the car has specific needs for each of these extreme configurations.
This vehicle produces so much power with a very fast response. That is also why the active aero features need to respond quickly to be able to provide the right amount of force on the ground for the power produced by the engines.
Which of these features are parts of the design of the AMG ONE are also found in Formula 1 or other racing series? Which aerodynamic design elements are common between the two?
So all of them and none of them, especially regarding Formula 1. What we share is the physics, components, materials, and the technology. Formula 1 has very strict and specific regulations, but we did not have to adhere to these with the AMG ONE. The design of Formula 1 cars is influenced by these changes in the regulations from season to season. In our case for the AMG ONE, we needed to fulfill certifications for road legality. We are very proud that we have achieved this, while also fulfilling the track requirements that we wanted to achieve. This was made possible by the use of active aerodynamics. There are no Formula 1 features that we can just ‘plug and play’ here, nor the other way around. We have to be very clear about the fact that this car is its own unique design. The features are more similar to our AMG GT3 race cars with a front diffusor, fender louvres, cooler positions, dive vanes on the underbody, wing, and rear diffusor. Its shape is optimized based on its own individual requirements and we didn’t want to replicate the look of a Formula 1 car.
Which of these features are you most excited about and which make the most difference for speed?
There is no single feature responsible for everything, each of them must work in conjunction with many others for this vehicle to drive properly and optimally. I am truly excited about the whole package, I can’t be excited about just one element here. Aerodynamics includes the entire car; we work with it as a whole. This entire vehicle, every hot spot, the battery, pumps, combustion system, all of these are provided with fresh air - this doesn't just involve the body of the car. It’s like having many children: you don’t prefer one over the other, it’s about the family. As a simple example, the connecting pillar for the rearview mirror at the door; it is curved in a specific way, not only for its effect on drag, but also for aero acoustics and rear downforce by redirecting this flow to the wing. Again, it is honestly impossible to be excited about just one feature.
Could you tell us about the usability of these modes during driving and how these look and feel for the driver?
There are three modes, one for driving legally on the street and the two others for driving on a racetrack. Pressing the “aero button” sets the vehicle at a lower ride height and creates the optimal conditions for the underbody to operate at maximum efficiency. The front diffusor flaps stow and provide the front diffusor with the proper shape, allowing the underbody to operate at its best. For the maximum downforce configuration, the fender louvres also are deployed in the same way as the wing and flap. This also, of course, creates a higher drag penalty. In the context of today's development, when higher speeds are reached where these driving dynamics features no longer need to be deployed, the fender louvres will stow to reduce drag, continuously providing the right aero balance and keeping the car “predictable”. In this case, this also means reaching VMAX faster.
The driver will not only feel this action, but will also see it, such as when the louvres change position. It's truly an exciting moment when we develop something that visibly produces the forces we're working for. Early on in development, we did consider hiding the fender louvres so that they would not be visible to the driver but we decided to make them prominent and design accepted the challenge.
What were the greatest challenges and triumphs in designing these features for the AMG ONE?
The challenge began when I got that phone call inviting me to the kick-off meeting. From seeing the concept for the first time, to shaping every single edge for efficiency and searching for functionality; from going through new ideas for higher performance, to defining the logic of the interactions – this whole project has been a challenge. Working together with the team that was built within this project, a family grew around this car. We wouldn’t have been able to reach the point that we have right now without the trust of our managers: we needed to make changes, go over limits and modify what we had already developed for series cars. In this case, we joined again the best of both the racing and street-legal worlds.
Could you tell us about the aerodynamic action of the air inlets on the body of the vehicle?
We have an engine compartment at the rear which requires a certain amount of air. We began with a great deal of discussion and brainstorming about how to get the amount of air that is required for this and the hot spots to the rear in an efficient way. There were many, many ideas. In the end, we came up with an aeronautical solution. We integrated it in a cohesive way with the rest of the car and gives it a personality that is visible from the rear. The two NACAS are placed above the engine compartment and rotated to get the right amount of air around the Green House - this is all integrated into the bodywork of the car. This air produced is in these areas and flows into heat exchangers underneath the cover tool. The air is released at the rear, drawn by under pressure behind the car.
How does the body shape of the AMG ONE compare to other low drag coefficient vehicles?
This cannot really be compared. We have very round shapes, expressive inlets in the front and rear, and the drag coefficient is not really lower in comparison to other models from Mercedes-Benz. There is one simple reason for this: In our High Way Mode, we want and need downforce. More downforce correlates with more drag. This is then not only about drag, but also about the Aerodynamic efficiency defined as the ratio between downforce and drag. We don’t have an extremely low drag coefficient, but it is low relative to the amount of downforce that we are generating. This is a very important point of relation between the two.
We see quite a lot of carbon fiber used in the AMG ONE. What is the advantage of using this material versus other lightweight but very durable materials?
From an aerodynamic point of view, we define the forces on the elements. The air goes through and around the elements of the whole car to produce these forces. We pass these forces on to the different departments that decide which materials to use. Please allow me to say something really extreme: The material matters less to me than the efficiency of the aerodynamics of the vehicle. Whichever material can achieve the forces needed, that's what should be used. For aerodynamics, whether carbon fiber is used or not, it's just a matter of efficiency of the weight and whether it needs to be reduced. An increase in stiffness and a reduction in weight are always needed. These two different directions require the use of new materials or new combinations of materials. That's how we get the best result for the whole package, meaning the lowest possible weight for this amount of force with the right amount of stiffness. This means that the lower the weight, the better the downforce can be applied. The same amount of downforce is then not compensating for a heavier vehicle, but on a lighter vehicle, can be applied to the wheels through the aero forces to achieve better performance.
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