About half way through the 98 model year, the Corvette gets a new option called "Active Handling".
The new Corvette Quarterly went out last week to subscribers and it contains an article on the system, so if you read that story, there is nothing new here. But, Chevy gives CQ such a big jump on the rest of the press, if you don't read Quarterly, then you have yet to hear about Active Handling. Magazines like Vette will have in-depth stories on it later this winter. What follows is a preliminary look at Active Handling.
Active Handling is a safety-related system that combines with traction control to further enhance the driver's control of the vehicle in aggressive or hazard avoidance maneuvers. Right now, the car uses rear brake intervention to control some extreme cases of rear wheel spin.
Active Handling takes brake intervention one-step further by using selective, single caliper brake applications to control gross oversteer or understeer situations in which the driver is liable to have trouble maintaining control of the vehicle.
The c5's Active Handling is the first application in the world of this type of system to a sports car. Previously it has only been used on expensive luxury sedans such as Lexus, BMW or Mercedes-Benz.
Additionally, it is the first stability enhancement system that is a performance driving enhancement *as well as* a safety enhancement. Lastly, it is the first of these systems that is switchable between normal (full-featured) mode, "competitive driving" (traction control disabled) mode and system full-disabled mode.
During an oversteer situation, Active Handling may apply the outside front brake to apply a yaw torque to the car, opposite the direction of rotation. During an understeer situation, Active Handling may apply the inside rear brake to apply an opposite yaw torque.
In early December, Chevrolet invited several automotive writers to visit the GM Milford Proving Ground and test the Active Handling system. These tests were run on Milford's Vehicle Dynamics Test Area aka the famous "Black Lake". Black Lake is a huge expanse of flat blacktop intended for handling test work. The closest thing I can use for description would be a large sports stadium parking lot with no light standards, planters, parking space blocks or marks.
At Milford there were a number of specific demonstrations GM engineers had set up.
- A 45mph lane change across two different surfaces. The lane change began on dry asphalt but finished on jenite, a kind of very slick-coated concrete, that had been wetted down.
- A 25mph slalom on wet jenite.
- A 50 mph double lane change
- A 65mph "sudden avoidance" lane change.
- A 55 mph slalom and 6) the Corvette "Challenge" course, a sort of long duration, medium speed autocross course. The first two were on wet surfaces, the rest on dry pavement.
To a driver of average skill level, the enhancement Active Handling offers in inclement weather, on poor road surfaces or in high-speed emergency avoidance maneuvers is significant and obvious.
To a driver with advanced performance driving skills, Active Handling can have that person meeting aggressive driving challenges in a more relaxed and smooth manner. Additionally, there are some avoidance situations were no measure of driving skill can maintain control of the vehicle, but the addition of Active Handling makes the maneuver possible. This is because, with the system off, the driver has steering, throttle and brakes with which to control but he/she cannot apply differential braking. The Active Handling system adds differential braking.
A great demonstration of that was the 65 mph evasive lane change which imitates a situation such as a concrete block or piece of pipe falling off a truck in the freeway or a deer running out on a highway at night.
In this situation, braking was not a viable option. This was a case of turn hard or die
I accelerated to 65 mph and approached an "obstacle" imitated by a four-foot wide line of traffic cones perpendicular to the direction of travel. I could not go straight but could turn hard right or left into adjacent "lanes". To add to the challenge, the GM person riding with me, (happened to be a buddy of mine, Brake Development Engineer, Jack Gillis) would tell me which way to go by shouting "left" or "right" just before I would "hit" the barrier. Each time I tried this with Active Handling turned off, I made the turn-in part of the lane change but then lost it on and "wrecked" ending up in a cloud of rubber smoke, surrounded by scattered cones. Gillis told me that no one, even GM ride and handling development engineers, had been getting through that maneuver with the system turned off.
Each time with the system on, the lane change was accomplished---with a pretty outrageous slide and lots of steering---but, nevertheless, accomplished and with very few cones giving their lives. Let me emphasize, here, that in this situation few humans are capable of controlling a car. You cannot compete with a computer's speed nor can you apply differential front braking.
The other four tests I was able to accomplish with either the system off or on, but it was obvious, particularly in the high-to-low coefficient lane change that Active Handling enhances safety and control of the vehicle.
The Corvette Challenge course is a "test track," marked with cones, Development engineers set up on Black Lake to evaluate the performance ride, handling and braking characteristics of Corvettes and other cars. I had driven C4s on this course several times in the last ten years but never had been on it with a C5.
In this situation, you set Active Handling in the Competitive Mode by bringing the car to a full stop then pressing and holding the traction control button for 5 or more seconds. In this mode, TCS is disabled, allowing you to use throttle to steer the car, but Active Handling's brake intervention remains available.
Unfortunately, timing equipment was not available, so my judgements as to lap time are subjective. I took a few easy laps on the Challenge course with the system off to kind of remind myself what it was like. Then, I took a several hard laps, again with the system off, to set my baseline impression. Next, I put the system in "Competitive" and ran hard again.
There is no question in my mind that with the system on, I got through the Challenge course just as fast but more smoothly and, on the last two or three passes, I may even have been quicker around the course. Bottom line: in a motorsports application that emphasizes handling, especially autocross, Active Handing in the Competitive Mode allows you to drive smoother and perhaps a measure quicker.
Once autocross sanctioning bodies begin to classify C5s, I wonder how they will address the issue of Active Handing on some cars and not on others.
Again, the system works by adding to the ABS/TCS modulator the ability to selectively enable the front brakes. All this is, of course, computer-controlled. The ABS/TCS computer equipment gets two more channels (for the two front brakes) some additional computer hardware and, obviously, a significant software upgrade. Besides the computer enhancements three additional sensors are on an Active Handling car, a yaw sensor, a lateral g-sensor and a brake pressure sensor. With the system fully enabled you have a very powerful combination of ABS, TCS and differential front braking.
I had read the Corvette Quarterly article on Active Handling before I made the trip back to Milford, so I had an understanding and some expectations of the system before I tested it. My expectations of the system's performance were met when I finally drove it. What I did not expect was how seamless its operation was. Only in the most extreme instances of brake intervention did I really feel the system working.
This seamlessness was very appropriate for a performance car.
Other systems of this type, such as Cadillac's two-channel "StabiliTrack" option or those on foreign luxury sedans are designed (perhaps figuring that drivers of those cars can easily get over their heads) to rapidly slow the vehicle with ABS as well as control yaw angles. The Corvette system controls yaw better than any two-channel system but does not attempt to slow the car's forward velocity as rapidly.
Active Handling is just another sign that, as John Cafaro said during C5 introduction video tape, "It's a great car with a great future."
If I was buying a C5, it would have no options other than: Z51, the six-speed and Active Handling.
Editor's Notes: Hib Halverson is currently writing articles for Vette magazine. To read Chevrolet's original press release about Active Handling, click here.
Copyright 1996 Barbara Spear
