2011 Porsche Cayenne S Hybrid: Suspension Walkaround
This time we're trying something different. Instead of shooting the 2011 Porsche Cayenne S Hybrid in my driveway, Kurt Niebuhr and I took it to our new garage space in Marina Del Rey, about 10 minutes from the office.
Yep, the Suspension Walkaround is going pro, first with a pro photographer and later (fingers crossed) with a real pro two-post lift so we can see EVERYTHING.
Yeah, I know it's kinda cool and ironic to see a 3-bazillion dollar sports car up on $10 jack stands in my driveway, and I'll miss that, but this setup should allow us to do more of the short-term loaners that come through our hands, like this one right here.
It won't happen right away and I still have a handful of driveway-shot walkarounds shot and waiting their turn, but for now I give you a peek at the future.
With a pro shooter like Kurt, who has a tripod and everything, we can do stuff like this. (wait and watch)
Yep, our Cayenne S Hybrid has air suspension with 5 height settings.
Position 3, the middle setting, is your normal everyday ride height setting. A step below that is Position 2, a sport setting that is automatically activated at higher cruising speeds to improve aerodynamics or it can be manually selected at any time by engaging sport mode. Position 1, the lowest setting, can only be used while stopped to ease entry and exit.
On notch above the midpoint is Position 4, a setting that provides a little more undercarriage clearance at normal speeds, such as you might want in fresh-fallen snow situations. Position 5 is the maximum clearance setting, and it can only be engaged in low speed off-road driving.
Compressed air is either injected into or released from the air springs to make these changes. We'll see more of them later.
We get our first glimpse of the front air springs directly behind the high-mount upper control arm of the Cayenne's double wishbone front suspension.
Here we can see almost everything, and most of the important bits are made of aluminum. The brake, brake rotor and wheel bearing all sprout from a large aluminum knuckle that spans from the upper control arm (green) at the top to the lower control arm (red) at the bottom.
A large stabilizer bar (black) comes in from the front, and the "coil over" air spring and adjustable damper (yellow) angles between it all and attaches to the lower control arm by means of a fork assembly that surrounds the front drive axle.
The air spring isn't really a coil over, of course, but it does surround the damper assembly in more or less the same way. But instead of a looping coil of spring steel, this Cayenne has a donut-shaped air chamber surrounding its dampers -- a 5 or 6-inch tall donut-shaped air chamber, that is.
You may have noticed the brake calipers were sitting forward of the axle centerline in the last shot. Here's why: the steering rack (yellow) acts behind the axle centerline, as it must in nearly every application where the front wheels are driven, be they front-drive vehicles or four-wheel drive machines like the Cayenne. The presence of hard metal fluid lines (red) tells us the Cayenne uses hydraulics to provide steering assistance.
The classic shape of the Cayenne's lower wishbone explains exactly where that name came from.
Every looked at a stabilizer bar and wondered exactly what's going on? The Cayenne's straightforward setup gives us a clear view. The stabilizer bar itself is a four-foot wide U-shaped piece of bent metal, with a broad straight middle section linking this side to the other.
When the body rolls, or tries to, the stab bar provides resistance to limit the speed and the amount body of roll.
In a right turn, the suspension on this side compresses relative to the body, and this compression raises the stabilizer link attachment point (yellow) which in turn pulls up on the arm of the stabilizer bar. The bar pivots in it's bushing (red) and that creates a torque that tries to rotate the straight central portion that spans to the other side of the car.
But the opposite is happening on the other side, where the body is lifting up, lengthening the shock and pulling down on the bar via its link.
And so suspension compression on one side and extension on the other create opposite forces in the arms of the bar, twisting the middle section and creating torsional resistance. That resistance is proportional to the diameter (to the fourth power) of the stabilizer bar's central span. We'll sometimes see weird bends to clear other components; they don't alter the basic operating principle much, but they do add a degree of inefficiency.
When both wheels hit a bump together, the links move in the same direction and no torsional resistance is generated; the bar pivots freely in its bushings. But if one wheel hits a bump, a torsion reaction will be momentarily created, which can magnify the jolt or twitch felt in the cabin. This is one reason (of many) why cars designed to provide ride comfort do not use large stabilizer bars, which in turn is one reason (of many) why they tend to have less than stellar handling. But too-big bars can also hamper handling if the surface is uneven and suspension impact movements are large. It's all a balancing act.
Air is added or removed from the air chamber via this hard line (white). The process is regulated by height feedback sent to the computer control unit from height sensors (yellow) located at all four corners of the suspension.
Stopping power, and there is a lot of it, comes from these 6-piston Brembo brake calipers.
These particular 6-pot Brembos use a closed-window design with two fixed bridges (red) for extra caliper stiffness. The downside of this design is the need to remove the caliper entirely (yellow) to change brake pads.
Functional brake cooling ducts are found in the Cayenne's front fascia.
In back, the Cayenne uses a multilink setup consisting of a stamped steel lower A-arm (green), a pair of aluminum upper links (yellow) and a toe link we can't yet see.
Here's your missing link, a stamped steel toe link (red). Easy toe-in and camber adjustments are made possible by these eccentrics.
Here we can see just how much the rear air spring/damper assembly is reclined. We can also see how much longer the rear-mounted toe link is in comparison to the lower control arm that sits farther forward. We see variations of this theme a lot on rear suspensions because the length difference creates dynamic toe-in as the car rolls onto the loaded side, which improves cornering stability.
Here's another look at the stamped steel lower control arm and the steel subframe to which it attaches.
Most of the tricky details of the air springs (green) are hidden inside the aluminum housing and dust bellows. Meanwhile, the rear stabilizer bar (white) is chock full of those crazy bends we talked about when we were looking at the front one.
It may take a few seconds to get your bearings. Here's a hint: you are looking straight down at the point where the stabilizer bar connects to its drop link (green).
Like we saw in the front, each rear wheel has a height sensor to help the air suspension system know how high everything sits.
Four-piston fixed Brembo calipers clamp onto ventilated rear rotors. Like the front, they use a closed window design with a pair of fixed bridges.
The Cayenne we've been looking at is a hybrid, so it rides on modest tires compared to other Cayennes: Michelin Latitude Tour HP in size 265/50R19. No tire and wheel weight this time; we're trying out a new shop and we haven't bought it its own scale.
Germans prefer lug bolts to lug studs, but then again they also like to go to Death Valley in summer and are known to wear black socks with shorts. *shrug* I'm not a fan.