Designing for Downforce | Lexus Monterey Peninsula

With an engine that delivers more than 450 horsepower,* the RC F—arriving in dealerships soon—will be the fastest Lexus outside of the LFA supercar. Several technologies will contribute to such performance, but one feature in particular benefits from more than 10 years of Lexus supercar research: the active rear spoiler.

Sometimes referred to as a “wing,” the active rear spoiler is an airfoil that pops up above 50 mph to create downforce—in other words, it helps press the vehicle toward the ground for enhanced grip and handling at higher speeds.

What makes the RC F’s active rear wing especially superb is both its elegance and its design history. It’s a direct adaptation of the LFA’s racecar-style active rear wing, which Lexus designed during endless 200-mph-plus test drives on Germany’s Nýrburgring race circuit. According to Paul Williamsen, national manager of strategic educational support for Lexus International, to fully understand the dedication Lexus puts into active rear spoiler design, and the experience it creates, one needs to understand how the systems came about.

During every heart-pounding minute spent flying around the Nürburgring, Lexus LFA test drivers helped shape the car’s final design by relying, as pro drivers do, on tactile feedback through their hands, seat and feet. In highly engineered cars like the LFA, this feedback gives professional drivers a subtle, almost sixth sense of what the vehicle is doing at any given moment, and how much further they can push it.

Working against them was aerodynamic lift, a phenomenon experienced by objects moving at high speeds over the ground. At initial test-track speeds, lift reduced the downward force on the LFA’s tires—the vehicle essentially rose, similar in principle to an airplane taking off.

“Drivers began to lose that tactile feeling of what the tires were doing on the roadway surface,” explains Williamsen. “It compromised the accuracy of the information coming to the drivers.”

As a result, the LFA track drivers and engineers developed the type of rear spoiler system found in the racing world, and designed it to provide maximum downforce—and therefore superior handling—for LFA owners. The final street-legal design is active: it stays tucked away at low speeds when lift is negligible or nonexistent (to avoid drag), and it automatically rises as the car approaches highway speeds.

Fast-forward to RC F development on the Fuji Speedway, which drew from this supercar design. Here, engineers and pro drivers took their supercar knowledge and designed a more subtle production version of the active rear spoiler. Like the LFA’s wing, the RC F’s active rear spoiler engages automatically at 50 mph and disengages at 25 mph; the lower threshold is to prevent the wing from rising and lowering repeatedly when the vehicle’s speed hovers around 50 mph.

In high-speed situations, like a track environment, RC F drivers can delay the wing’s deployment by selecting the Eco driving mode (less drag equals less fuel burned). There’s also an override that allows the driver to raise or lower the spoiler—useful, say, if there’s glare coming off the wing while cruising the highway at sunset, or when washing the car.

The RC F’s active rear spoiler comes standard, but note that there’s an enhanced version that comes with the optional RC F Performance Package, which includes an active rear spoiler that’s partially constructed from the same tough but light carbon fiber as the LFA’s wing. As with the supercar, this helps reduce overall weight for enhanced performance

Looking to the future, Williamsen expects to see the active rear spoiler appear on other Lexus performance models. “Our designers and aerodynamicists have learned a lot about the active wing working with the LFA over the past years,” he concludes. “It makes sense for the technology to trickle down like this.”

Post courtesy of Clark Heideger.