Air Suspension & Active Suspension Mangement

[CTS]

Question for those in the know:

I would appreciate someone explaining some of this system's functional intricacies, as I find my observation of its operation troubling. For example, when you adjust the ride height at a standstill or at slow speed, the movement is very slow and seemingly labored. This reaction time seems 'adequate' for moving from the highway to an off-road environment. But in PCNA literature, they say that "in high performance road scenarios, the system automatically suppresses the pitch and roll"...etc., etc.). How is it that a system, which takes a half hour to move 4", is going to compensate for plunging into a massive understeer situation with significant suspension loading in a fraction of a second?

Given my lack of knowledge, I could only hope the system, while stationary or at slow speeds, "saves itself" operationally for times of real need??? (Is this turn "Pressureworthy"? -- Sienfeld Reference)

Thanks!

[stumpjumper]

Question for those in the know:

I would appreciate someone explaining some of this system's functional intricacies, as I find my observation of its operation troubling. For example, when you adjust the ride height at a standstill or at slow speed, the movement is very slow and seemingly labored. This reaction time seems 'adequate' for moving from the highway to an off-road environment. But in PCNA literature, they say that "in high performance road scenarios, the system automatically suppresses the pitch and roll"...etc., etc.). How is it that a system, which takes a half hour to move 4", is going to compensate for plunging into a massive understeer situation with significant suspension loading in a fraction of a second?

Given my lack of knowledge, I could only hope the system, while stationary or at slow speeds, "saves itself" operationally for times of real need??? (Is this turn "Pressureworthy"? -- Sienfeld Reference)

Thanks!

if I remember correctly, you're actually talking about two different pieces of the suspension, the air spring which controls height, and the electronically controlled hydraulic shock absorber, which controls bound and rebound by opening and closing internal valves

my understanding is that it's the shock absorber that's adjusted in those situations, the same as it would be in normally spring adjustable suspensions

[CTS]

Yes, I understand the function of variable damping and the effect of it, but I was under the impression (from the dealer) that in etreme situations that the air suspension would actually work to make adjustments as well (fully active suspension). Simlar to a sway bar perhaps (tucking into wheelwell on inside wheels or raising outsides). This is what the dealer seemed to represented -- I may have also misunderstood.

So, the air suspension does nothing except raise and lower the vehicle in a very slow way to achieve a level ride height at the predetermined height, and the PASM is varible shock damping only. This supports my observation. Thanks.

[stumpjumper]

Yes, I understand the function of variable damping and the effect of it, but I was under the impression (from the dealer) that in etreme situations that the air suspension would actually work to make adjustments as well (fully active suspension). Simlar to a sway bar perhaps (tucking into wheelwell on inside wheels or raising outsides). This is what the dealer seemed to represented -- I may have also misunderstood.

So, the air suspension does nothing except raise and lower the vehicle in a very slow way to achieve a level ride height at the predetermined height, and the PASM is varible shock damping only. This supports my observation. Thanks.

I can't comment on the Cayanne specifically, but for Audis that's how it works on the A8 and RS6, the air suspension works the same way on the allroad but it doesn't have active dampening

[mudman2]

The active suspension does use the air springs to control attitude, reaction times are better than analogue (steel springs) as it uses force and motion sensors to predict action / reaction. It does lean into the curve as you describe.

The Porsche Cayenne Technick is a great book which describes its operation.

The raise lower function is seperate.

Its slalom type manouvers it thrives for such a beast.