Big Leagues

Tradition dictates that state-of-the-art automotive technology arrives first in expensive luxury cars and after many years then filters down to more mainstream models.

So it's encouraging to see a high-volume, inexpensive vehicle debut with a technology every Ferrari and Maserati driver started enjoying only recently.

Such is the case with Adam Opel AG's new Astra compact car, which offers an optional semi-active electronic chassis control system that is nothing short of remarkable.

ZF Sachs AG supplies the Continuous Damping Control (CDC) suspension, which Opel markets under the name IDS Plus. The vehicle went on sale March 20 in one of Europe's most competitive segments.

ZF Sachs supplies the MacPherson struts for the front wheels and twin-tube shock absorbers for the rear, as well as three body acceleration sensors, two wheel acceleration sensors and an electronic control unit to serve as the brains behind the system.

The ECU processes signals from the five sensors, interacts with the antilock brakes and electronic stability control (ESC) unit and integrates information such as steering wheel angle, brake pressure and engine torque.

With all that information, the CDC controller is capable of tuning the necessary damping force — via proportional valves at the base of each hydraulic damper — for optimum handling, regardless of road conditions.

The continuously variable system reacts to inputs within milliseconds. Accelerate hard, and the system increases damping of the rear wheels, counteracting the vehicle's natural tendency to “squat.” Brake hard, and the damping is boosted in the front, preventing excessive “nose dive.”

On the Astra, a button on the instrument panel allows drivers to choose between a normal, comfortable ride and a “sport” setting that instantly tunes the dampers for a stiffer feel.

On the software side of the equation, CDC employs the “Skyhook” strategy. Its goal is to suspend the vehicle from an imaginary straight rail in the sky, allowing it to float effortlessly above any potholes, bumps or uneven pavement. The control module provides the proper level of damping to ensure the smoothest possible ride.

In aggressive driving situations, CDC keeps the vehicle on a stable course during hard cornering, even before an intervention of the ESC system.

Some drivers are more apt than others to force the ESC into action.

Germany's Joachim Winkelhock, who had a long career in racing, including a 1989 Formula 1 stint, demonstrated the extreme capabilities of the CDC-equipped Astra at the ATP Proving Ground in Papenberg, Germany, a small northern shipbuilding town.

Winkelhock took journalists on a tight handling track at the proving grounds and showed how the Astra stays stable and well composed, even when dashing into a tight curve in excess of 70 mph (110 km/h). In a hard right-hand curve, the CDC tightens the damping force on the left-side wheels, and vice versa.

“ESP keeps the car stable,” Winkelhock tells Ward's after a test drive. “It makes the car much safer and easier to handle for average drivers.”

In other driving maneuvers at the ATP Proving Ground, journalists performed double-lane changes, drove through a slalom course and traversed a handling course with cambered and uneven pavement.

The Astra executed each maneuver as well as or even better than more expensive (and admittedly larger) vehicles, including the Audi A8, BMW 7-Series, Maserati 3200 Coupe and the Volkswagen Phaeton.

All of those luxury vehicles feature CDC, which first appeared on the market in 2001.

CDC is standard on the A8 and Phaeton and all Ferrari and Maserati vehicles, and it's optional on the 7-Series, Porsche Cayenne and VW Touareg. Take rates for CDC have exceeded 50% for Cayenne and Touareg and are as high as 60% on the 7-Series, ZF Sachs says.

With its continuously variable nature, the system maximizes wheel contact with the road, which minimizes braking distance and reduces lateral acceleration.

ZF Sachs worked on CDC with Astra's brake supplier, Continental Teves AG & Co. CDC is exactly the type of “global chassis control” that brake suppliers Continental, RobertBosch GmbH, Delphi Corp. and TRW Automotive are striving for in an attempt to minimize vehicle rollovers.

The price is one of CDC's most attractive features: IDS Plus sells in Europe for €395 ($484) and can be had on a nicely equipped vehicle that sells for less than €17,000 ($20,800).

With CDC, Astra has raised the stakes in its European battle with Volkswagen AG's all-new Golf, which has been roundly criticized in Germany for being overpriced, and it doesn't offer a semi-active suspension such as Astra's.

With the Opel contract, ZF Sachs predicts 8% of all Astras sold in 2004 will have CDC, and that the take rate will rise to 12% in 2005. Werner Balandat, ZF Sachs' director-Advanced Chassis Systems Suspension Div., tells Ward's he expects the take rate to reach 20% within two years.

The company's Schweinfurt, Germany, plant has capacity for 1.3 million CDC dampers on two assembly lines, and Balandat says the company is ready to boost capacity in the 2006 timeframe. “We are prepared to expand,” he says.

The supplier is charting impressive growth for CDC, from 15,100 units in 2001 (the first year of production) to 121,000 units last year. By 2005, ZF Sachs expects to produce 226,000 CDC units.

To date, ZF Sachs has no U.S. contracts for CDC, but it is eager to land one. Company officials say they have installed CDC on a Cadillac Seville STS as a prototype for General Motors Corp. in hopes of winning business with the No.1 auto maker.

Cadillac already has a similar semi-active suspension, supplied by Delphi Corp., called MagneRide. The system uses magneto-rheological fluid, supplied by Lord Corp., to instantaneously vary the pressure within the dampers.

Cadillac offers MagneRide as optional on the SRX cross/utility vehicle and STS sedan, and it's standard on the new XLR roadster. GM also offers MagneRide as optional on the Chevrolet Corvette.

It's curious that GM opted for ZF Sachs' CDC system for the Opel Astra, even after several years of experience with Delphi's MagneRide. It's possible the two suppliers will be in stiff competition for future Cadillac business.