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MagneRide 4.0 is nothing short of magical. Here’s how it works.
Most of the talk around Cadillac’s two new sport sedans has to do with their drivetrains. The Blackwing versions of the CT4-V and CT5-V are likely to be some of the last manual-transmission performance sedans we’ll see; the CT5-V Blackwing is the only manual V-8 sedan on sale today. But the really impressive stuff is found in the chassis.
The CT4 and CT5 share an updated version of GM’s Alpha platform, creatively named Alpha 2. The big step forward is with the dampers. The Blackwings both come standard with the latest MagneRide dampers, and I’m convinced they’re magic.
Cadillac introduced MagneRide on the Seville STS in 2002. Originally developed by Delphi and now made by BWI Group, the fourth generation of MagneRide debuted on non-Blackwing versions of the CT4-V and CT5-V. MR 4.0 is available on the 2021 Cadillac Escalade, and will come standard on the upcoming C8 Corvette Z06. But to understand what makes MR 4.0 so special, we have to explain what MagneRide is in the first place.
A conventional passive automotive damper has a piston that moves up and down within a cylinder filled with oil. The rate at which the piston moves is determined by the shape of the piston itself. (Our colleagues at Car and Driver have an in-depth guide to how dampers work.) Passive dampers aim for compromise, balancing ride comfort against handling. A basic adaptive damper might have a solenoid that can change the piston valving, allowing for two or more selectable firmness settings.
MagneRide dampers are constructed like traditional passive dampers, but they’re filled with magnetorheological fluid—oil filled with tiny iron filings. Electromagnets in the piston generate a magnetic field that alters the orientation of the iron, changing the viscosity of the fluid and altering the damping stiffness. With no current, an MR damper responds like a traditional passive damper, but with enough current, the fluid can theoretically get so thick, the damper would act as a solid element. In between the softest and stiffest settings there’s an infinite amount of variability. And the stiffness can be changed very quickly because all you need to do is alter the current regulating the fluid. Plus, each damper can be tweaked independently, giving individual control over each wheel of a car.
“That’s the biggest thing with suspension tuning and technology, it’s always been a move to decouple motions,” says Bill Wise, technical lead performance engineer on the Blackwing sedans. With passive dampers, “your wheel events, your curb strikes, your heave events, your jumps, your rolls, they all have to be arrested by four dampers that have no idea what the car’s doing.” This necessarily leads to compromise.
Suspension engineers talk in terms of pitch (front-to-back motion, nose up or nose down), roll (side-to-side motion, “body roll”) and heave (full-body up-and-down motions, like you get from cresting a hill or bottoming out.) “The big thing with MR is, you can remove the single-wheel events and the curb strikes from your body motions—your pitch, your roll, and your heave—because MR is so much smarter in knowing what the car is doing,” Wise says. “So you can make the car incredibly stiff when you need it to be, when you need to load the tires or [manage] low speed body motion—your pitch and your roll—when you’re really sensitive to the vertical load on the tire. But at the same time, you can be soft so that when you hit things, those events don’t affect the vertical load and the tire so much. You can really balance the forces better.”
It’s an incredibly powerful tool. “At the beginning of MagneRide, I used to do a little demonstration on a C4 Corvette prototype,” BWI’s Darrin Delinger, a longtime MagneRide engineer recalls. “I would push down on the rear quarter and hold it in place, and turn the damper on and it would hold it there. Then when you flipped it to soft, the corner would spring up.”
On MR 4.0, BWI made some changes to the magnetorheological fluid, but the big improvements are in the new Inertial Measurement Unit (IMU) that identifies body motions. Engineers also got rid of the wheel-position sensors in favor of hub-mounted accelerometers, which Dellinger says provide better input signals.
“With wheel position sensors, we had come up with a patented filtering mechanism to determine heave, roll, and pitch of the vehicle body from wheel position,” Dellinger says. “While that was a very good estimate, there were times in special situations where it would do things that would cause the signal to go out of phase, let’s say, because it’s a filtered result.” Basically, the filtering needed better tuning.
On the latest version, the MagneRide ECU processes a lot more data than before, and that data creates a much clearer picture of what the body and tires are doing. Processing power has also come a long way. “There’s an immediacy to MR that is now available to us that wasn’t there before,” says Wise. “Before, you were almost always trying to catch events, because you had this latency. Now you can be a lot more proactive. You can do a lot more early on. So you can respond to wheel events faster and not have to produce as much control, which in the end allows you to effectively do more with less.”
The car reads the road surface 1000 times a second and reacts to changes almost instantaneously. This speed allows the MR system to mitigate body roll without the rough ride of stiff stabilizers. The system even has temperature compensation so the responses stay the same no matter the temperature of the damper itself.
Of course, your input signals are only as good as what you do with them—”with great power comes great responsibility,” Dellinger quips—so the hardware is only part of the magic. It takes deft programming to achieve the right balance, maximizing tire grip without creating unnatural sensations. In the Blackwings, MR 4.0 doesn’t keep the car perfectly flat all the time. There is still body roll, heave, and pitch, but it’s very precisely controlled. This makes the driver aware of what the car is doing, while still keeping bigger motions in check. The result is almost unbelievably good body control, with nice soft edges and no abrupt sensations. On the road, the ride-handling balance is Lotus-esque. In other words, magic.
Cadillac invited journalists to drive the CT4-V Blackwing and CT5-V Blackwing on track at Virginia International Raceway. On the track’s short and not-entirely-straight front straightaway, the CT5-V Blackwing was approaching 150 mph before a hard brake down into turn 1, where entry speed was around 45 mph. In a 4100-pound car, this could be terrifying, even with the optional carbon ceramic rotors. In heavy braking events like this, the IMU increases front rebound and rear compression damping to generate extra stability. Very clever.
I won’t soon forget the way both Blackwings launched over the jagged curbs on VIR’s fast climbing esses. Both models handled that roughness with stunning grace. “That’s where the ability to decouple the ride events really comes into play,” Wise says. “There’s a base level of control that we basically always run. But then as you see these other events, we start passing the baton to other parts of the algorithm that then take over.”
The aggressive line through the climbing esses has you basically flying over the curbs. Wise breaks down how this looks to the IMU. “It starts as a roll because you’re pretty heavily loaded. So the roll tables are taking over at that point and they’re giving whatever output that we’ve requested them to do. Then when you see the curb strike—and effectively what ends up being four wheels up in the air and then back down—the heave table starts to take over, and we can shape that curve such that the velocity of the body motion is taken into account. That’s a very high speed event with a very sudden vertical input, and what we do is add a bunch of control right at the beginning. So when we see the real quick deviation, the real fast motion of the body away from the wheels, we can add a bunch of control…. Then, based on the fact that that curve is velocity-based for the body motion relative to the wheels, as the car comes back down and the velocity settles, we can start pulling that control back out.” (Note: When Wise talks about “control,” he basically means damper stiffness.)
Wise likens it to catching a bowling ball. You put a lot of force into slowing the ball immediately, then relax.
As with all of GM’s hardcore performance cars, the Blackwings come with Performance Traction Management (PTM), among the most sophisticated traction control systems available on a production car today. With PTM activated, the engine, brakes, electronic locking differential, steering, and MR dampers all talk with each other, the various systems making adjustments as needed to maximize grip. Wise says the quicker responses of the MR 4.0 dampers led to some big changes in how PTM works.
“Corner exit is a specific case where the car is loaded up, you’ve got roll in the car, you’re going to apply throttle, so you’re going to get squat in the rear axle,” Wise says. “So that’s one of those spots where we’re able to […] decouple the motions of a corner-exit event from a mid-corner heave event. That’s one of the huge advantages there. We can get really specific with how the car is going to put weight on the rear axle, how it’s going to load those tires, such that we don’t blow the tires off too quickly.”
In the case of the CT5-V Blackwing, which sends 668 hp from a supercharged V-8 to the rear tires, this is quite important.
“To tell you the truth, sometimes I say that driving MagneRide cars makes me a little bit lazy,” Dellinger says. “When I get into other cars that aren’t as smooth or whatever, it’s like, ‘Oh my goodness, all this is going on?’ And my workload goes up a little bit.”
That’s the amazing thing here. MR 4.0 dampers change so much in real time, but the end result is just a really well-sorted car. There’s a lot going on beneath you, but it all feels so natural, you tune it out and get on with the business of driving. First you revel in the way a Blackwing takes the curbing on VIR’s climbing esses; then you focus on carrying more speed, taking more curbing.
Perhaps the most exciting thing is that this is only the beginning for MR 4.0. As mentioned earlier, the new Corvette Z06 gets these shocks, and Bill Wise is on the development team. As for me, I’m still not convinced they’re not magic.
The Suspension Technology That Makes the Cadillac Blackwings Drive Like a Dream – RoadandTrack.com
Our car experts choose every product we feature. We may earn money from the links on this page.