How the Mercedes-Benz Vision EQXX scores its incredible 0.17 Cd
The Mercedes-Benz EQS already has the lowest coefficient of drag — 0.20 Cd — of any current production car on sale, but Mercedes can do better, and it’s done exactly that with the Vision EQXX. This technology project achieves a final Cd of just 0.17, and it does so with a body that is even more aesthetically pleasing than that of the EQS.
In fact, the Vision EQXX looks much more like a sports car than it does a blob of efficiency. That’s downright commendable, but it’s also less of a surprise than it may seem. After all, the shape of a supercar tends to be a rather aerodynamic one if you remove the giant wings and splitters that typically adorn them. Going even further, the Vision EQXX’s design isn’t way out there in concept land. This legitimately looks like a car that Mercedes-Benz could put into production. It even has mirrors and door handles! Will Mercedes ever do such a thing? The company has given no indication that it will, but be that as it may, this design is serious enough that we wanted to know everything about how designers and aerodynamicists achieved the 0.17 Cd.
For starters, there’s the car’s shape/silhouette. The Vision EQXX might technically be a four-door sedan, but it’s not shaped like any traditional three-box design you might expect from an S-Class or C-Class. That’s because the traditional three-box sedan design is not the most aero efficient shape you can make — Mercedes-Benz Chief Design Officer Gordon Wagener even told us that EVs could very well mark the end of sedans as we know them today for that reason. See both the EQS and EQE as Mercedes-Benz examples. To be more aero efficient, you’re much better off with a teardrop roofline that tapers all the way back to an abrupt tear-off edge in the rear. Mercedes optimized that teardrop shape for the EQXX Vision, perhaps to a fault.
The lower roofline in the rear appears to directly cut into rear passenger space, as headroom is compromised. That’s less of a problem for a compact car like the Vision EQXX that may not often carry rear passengers, but for cars like the EQS that are meant to have luxurious rear seats, that roofline needs to be punched far higher up. It’s a game of give and take, and it’s one we expect to play out as manufacturers attempt to reduce drag to gain more range for their EVs. One way Mercedes says it’s able to combat that roofline is to simply lean the seats back at a more aggressive angle, which it does in the EQXX to allow more headroom.
Beyond the obviously slippery shape, there are details aplenty in the Vision EQXX that help it achieve the 0.17 Cd. Up front, the frontal area is less than the CLA and the Smart EQ ForTwo. The subtle breathers on the sides of the front bumper are meant to pair with the wheels to reduce drag. Wheels and tires are big pain points when it comes to drag, but the Vision EQXX adopts super thin and tall (20-inch) wheels and tires. Bridgestone Turanza Eco tires are further optimized with special aerodynamic sidewalls, and the wheels themselves are made of forged magnesium with covers to allow smooth airflow over them. Mercedes being Mercedes, those covers are transparent so as to still allow viewing of the rose-gold-accented wheels below them.
You may be wondering, where are the wheel spats? Turns out, Mercedes trialed that idea, then threw it out for aesthetic reasons. It would force the already 50 mm track reduction in the rear to be an even larger track reduction, so Mercedes decided to go without. The goal was to make an efficient and beautiful design, and beauty won this round.
“The spats have a problem that you need to increase the boat-tailing in the rear even more, so the difference between front and rear gets even bigger,” says Teddy Woll, head of aerodynamics at Mercedes-Benz.
One neat piece of technology in the rear of the car is the active rear diffuser. It allows Mercedes to optimize the tail end of the car no matter the speed you’re traveling. Once you hit 37 mph, the diffuser moves out in two steps and improves higher speed drag.
“It folds down into a ramp angle, and then it folds out to ensure the perfect tuning of the rear,” says Woll.
It’s even designed to retract when it senses an impending crash, though Mercedes won’t say if it’s considering the active diffuser as a production item yet.
There’s also the matter of wind tunnel development. Mercedes says that it used about one-third of its usual wind tunnel development time for the Vision EQXX, because of its ability to do development work using augmented reality and virtual reality. That Mercedes was able to accomplish this low Cd with even less wind tunnel time than usual makes it all the more notable.
Perhaps what’s most impressive of all when it comes to the EQXX is that Mercedes has put together an incredibly efficient car that looks like something you’d want to be seen in. It’s alluring, attractive and everything we’d expect a Mercedes-Benz to be.
“In line with our philosophy of Sensual Purity, we created spectacular proportions that combine beauty with efficiency,” says Wagener. “The resulting body flow delivers revolutionary aerodynamics. The fact that the end result is as beautiful as it is bears testament to the skill of our design team working in close collaboration with the aerodynamics experts.”
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