Slip slidin' away: Cadillac ICCS keeps you on straight and narrow

PHOENIX -- While Cadillac's big news for the '97 model year will be the German-built Catera, engineers from General Motors Corp.'s Cadillac/Luxury Car Div. have been busy refining the integrated chassis control system (ICCS) for up-level versions of its front-drive models: Seville STS, Eldorado ETC and DeVille Concours.

Antilock brakes and traction control have reduced collision risks, but when you remember that the footprint of even the newest and cutting edge tire is about the size of an 8 1/2 by 11-in. sheet of paper, losing control on snow and ice, or sand-swept desert roads, remains a real possibility.

Developed by GM's Delphi Chassis Systems, ICCS goes one step beyond antilock brakes. By using a "yaw rate sensor" located beneath the parcel shelf and above the rear axle along with another computer chip known as a "lateral acceler-ometer," tucked underneath the passenger seat, ICCS automatically corrects for oversteer or understeer.

Imagine taking a sharp hairpin curve to the left on an ice-covered country road and the rear end begins to fishtail. Speed sensors attached to each wheel detect a difference between the speeds of the two front tires and send that information to the yaw rate sensor, which, in turn, responds with a signal that applies the brake at the right front wheel. That enables the left front wheel to pull the rear out of its skid.

During a recent ride-and-drive at Phoenix International Raceway, writers tested the system on a challenging course that included soapy water, tons of sand, gravel and a variety of crash-avoidance maneuvers.

Taking a 140-degree turn into a sudsy puddle guarantees that you'll lose control. Then as the Seville STS skids to the right, suddenly the car is heading into a 100-ft. (30-m) stretch of sand nearly a foot deep. As careless as I want to be, there's no way I could do a 360, or even a 180-degree spinout.

To provide more vivid evidence of what these little computer chips can do, some test cars had a switch that could turn off the ICCS. Now, a 360- or even a 450-degree spin becomes a piece of cake.

For a competitive perspective, the folks at Cadillac offered a Mercedes-Benz S500, equipped with the German automaker's Electronic Stability Program (ESP) -- similar to, but more aggressive than, the Cadillac package.

Developed jointly with Robert Bosch GmbH, the ESP recently captured the 1996 Discover Award for Technological Innovation. It is standard on Mercedes' V-12 powered models and optional on its V-8 cars, including the new '97 E420 sedan.

Although the ESP system seems to seize control of the car, especially in a 360-degree turn on a slippery surface, Cadillac's ICCS gives the sense that a driver's performance still matters.

"The basic goal was to find a way to intervene to maintain control only as certain dynamic limits are exceeded," says Robert L. Reuter, group manager-chassis electronics for Cadillac/Luxury Div. "And we wanted that feedback to be as gentle as possible."

The final dimension in ICCS's refinement is another computerized feature called road texture detection. This enables the car to measure the road roughness and adjust the brakes in 0.001 to 0.002 second, or about 1,000 times faster than traditional antilock brakes. That translates into shorter stopping distances on rougher surfaces.

None of this eliminates the chance to overcome the laws of physics through extremely aggressive driving, but it shrinks the risk significantly. In a couple of months, when Cadillac releases its '97 prices, we'll see how much Caddie thinks it's worth to front-drive luxury-car customers.