"Sky Hook," Mike Neal told us, "is one of MR's main algorithms. Based on it, MR commands some force level at each shock, separate at each corner and specific to compression or rebound. This is done in an attempt to make the car not heave, pitch, nor roll. Sky hook is a body control algorithm. We have others for wheel control which give us different damping forces.
"Separate from those fundamental algorithms, we have a bunch of others. If you're getting to the end of the travel, we have algorithms which recognize that then do something to reduce impact on the bump stop. We have algorithms that compensate for temperature...algorithms which condition the signal to smooth transient spikes and things like that."
Once MagneRide's sensors gather data and its controller processes it with the proper algorithms, four electrical drivers adjust current flow to the electromagnets in the shocks, which vary the magnetorheological effect to provide the correct damping. This could be damping to improve ride, to improve handling, or to limit frontend lift during acceleration or dive during braking.
The driver has some input to the controller via a two-position switch. In the "tour" position, the MR controller emphasizes the sky hook algorithm when setting shocks and when switched to "sport", it emphasizes wheel control.
What's it Like Out There?"If you're on a smooth road," Mike Neal told us, "while you'll notice better isolation, MR's advantages to handling are minimal. It's on roads which cause large ride events and body motion where it has huge benefits.
"Go to a place like the Nrburgring (a famous race track) in Germany, where the track has lots of dips and undulations and you're takin' every turn at 100 mph or faster. At that speed, it doesn't take much of a ride event to really heave the car, pitch it and roll it around. In a place like that, MR is a huge advantage."
North of Los Angeles are the San Gabriel Mountains. About 8 miles into the San Gabriels on State Route 2, hang a left on LA County N3. After about 30 miles, you're in the desert town of Palmdale and you'll have been over some of the better roads for high-speed touring west of Nrburgring.
I drove an MR-equipped '03 Convertible, a perfect choice to see how MR works in the real world. N3 had lots of heaves and undulations of different depths, heights and lengths. There were a few Nrburgring-style, bumpy 100-mph turns, too.
It was easy to feel Magnetic Selective Ride Control doing its thing. Compared to a base Corvette, it was like night and day. Compared to the '97-02, Real Time Damping system, MR has improved wheel control over the higher frequency (10-15 Hz) ride movements because it can bring more damping authority to bear and it can switch damping levels more quickly. The system effectively damps the big heaves, pitches, and rolls that come from bumps and dips or low spots on the edge of the road. Thirty miles, running hard over N3 sold me on MagneRide.
Does MR have shortcomings? Really high frequency (17-20 Hz or more) stuff, little ripples on concrete highways or washboard/chatter-bump surfaces, are a slight problem. In a straight line, the ride is a little harsh over sufaces like that. At high speed and at high lateral acceleration over chatter bumps, the car wants to skate sideways.
MR seems to be less effective in damping this kind of harshness presumably because, even with a 10 millisecond response time, with the car moving fast, it can't react quickly enough to bring the most ideal damping to bear. While this harshness is a shortcoming, the types of surfaces that cause it are rare and it might not be entirely an MR issue. The stiff sidewalls of C5's run-flat tires amplify harshness to the suspension. C6 will arrive in 2005 with a new, Goodyear EMT having improved harshness qualities, which might solve this problem.