Lateral Thinking

Why CT 200h Chief Engineer Sam Sadakata thought long and hard about one key feature: dynamic dampers.

OBVIOUSLY, HE THOUGHT about size. Obviously, he thought about the hybrid drive. And obviously, he thought about what kind of driver would be itching to own a Lexus CT 200h when it hits dealerships in a few weeks.

But not so obviously, at least until you get a chance to grab a test drive, is that the vehicle’s chief engineer, “Sam” Sadakata, spent a great deal of time thinking about suspension—or, more precisely, how to keep it in check.
> Related: Sadakata Introduces the CT 200h

By now, you may have heard about the CT 200h’s version of a selectable driving mode system, which allows you to switch the vehicle between Normal, Eco, and EV modes (aka the “blue light” modes), as well as Sport Mode for the accelerator-inclined—this is the “red light” mode that basically allows the driver to fully capitalize on the CT 200h’s combination of zero-rpm torque and ability to zip around like a jack rabbit.

The sporting proposition is partially the doing of a feature Sadakata and his team spent long hours perfecting: a new kind of suspension damper system that’s key to what Sadakata calls the “fun to drive” aspect of his little luxury hybrid.

THE CONCEPT
The relationship between body rigidity and handling is simple and direct. The more rigid a vehicle’s body, the easier it is to control the unwanted variables of suspension and wheel deflection caused by body flex, or the vehicle’s tendency to lean and sway when you attempt to turn it on a dime.

“So as part of the process of delivering a bit of driving fun, we naturally started off by working on increasing body rigidity,” says Sadakata. “But we ran into difficulties.”

THE CHALLENGE
“You can only go so far with rigidity before you start to encounter vibration,” he explains. “The frequency of that vibration gets higher and more insistent. It’s a common deadlock that every car maker experiences when building a dynamic car.”

The usual solution, Sadakata tells us, is to connect the tops of the front suspension towers by means of a solid lateral link, also known as the strut brace. This is a well-established and popular technique for improving handling.

THE LEXUS SOLUTION
However, the CT 200h takes the strut brace solution a step further. Its individual suspension components (both front and back) are laterally connected to deliver the requisite degree of body rigidity (see illustrations). But rather than the normal solid braces, the CT 200h’s lateral performance dampers are hydraulic.

These dampers bring an element of flexibility and adjustability to the CT 200h’s still-rigid chassis setup, which conventionally braced cars simply don’t have. Better yet, they quell high-frequency vibrations.

“Technically, they are like shock absorbers in that they consist of a spring with oil to attenuate the vibration,” says Sadakata. “They are different from a normal damper in that the lateral damper operates at very high pressure. As the vibration intensifies, the damper works like a shock absorber, turning vibrations into heat energy.”

THE RESULT
“At first I was quite skeptical until I test-drove a vehicle with and without the dampers,” says Sadakata. “It was compelling, a real turning point. Right away I decided to use the system on the final CT 200h.”

You’re obviously going to have to check it out yourself, but Sadakata has no doubt that these dampers can improve handling significantly, making the car sharp, smooth, and fun to drive. They also help reduce road noise, as well as improve steering feel and comfort.

“We’re really happy to have discovered such a great application for the lateral damper mechanism in the CT 200h,” says the chief engineer. “It’s a win-win result.”