Old-Guy wrote:The VSX's suspension is still a bit of a mystery to me.
As I understand it:
- In the VSX, the standard 6 sphere arrangement, which (I think) I understand thoroughly, is supplemented by two extra spheres, one in each (front and back) suspension circuit,
The four corner spheres (which have been replaced not that long ago) are harder than standard,
Correct. The main difference in the corner spheres from a standard model is the damping valves - the bypass hole is much smaller and the leaf valves are stronger as well. Together it makes the damping MUCH stiffer. The front suspension has 5 bar lower pressure but the rear is the same as standard, so the spring rate isn't much different.
The supplementary spheres are normally in circuit,
There's a suspension ECU, that can lock out the supplementary spheres by means of an electrovalve in each circuit,
The ECU energises the electrovalves either when the console button is in 'Hard' mode or when the roll angle measured from a pair of sensors, one at each end of the front ARB, indicates that that the driver is pressing on.
For a 30sec after any door is opened.
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Is this right, as far as it goes?
No not really.
The supplementary spheres (officially called "hydractive regulator sphere", or sometimes "centre sphere") are normally in circuit during driving yes, but the hard mode is actually the hydraulic/electrical default mode, so that's what you'd get if you unplugged the fuse to the Hydractive computer. It's only by keeping the electrovalves energised for the majority of the time that you're driving does it enable soft mode.
No power to the electrovalves puts the system in hard mode - not only is the additional sphere isolated, but the left and right sides are cut off from each other as well, which means oil can't flow from side to side which further reduces body roll.
With power to the electrovalves the additional sphere is connected to both sides through two damper valves. The sphere itself has no damper valve (its basically an accumulator sphere at a slightly different pressure) but the block that it screws into has two normal sphere like damper valves - the sphere connects to the junction of the two, and each damper valve goes off to one side of the suspension.
These damper valves are quite softly tuned compared to the ones in the corner spheres so in the soft mode you have much softer damping but you also have a softer springing rate as well because the extra gas volume switched into circuit changes the springing rate.
There's a bit more to it than that, for example large bumps are mostly absorbed by the corner spheres even in soft mode, while the additional sphere provides most of the soft/floaty ride quality and absorption of small bumps, which means that the rebound rate is actually dynamic depending on the intensity of the bump - the rebound from small undulations is gently damped (good ride quality) while the rebound from large undulations is heavily damped. (good body control)
As for when it switches between modes, no the computer does not measure actual body roll (not even on an Activa!) as there is only one roll bar sensor on the front roll bar. This so called "body movement sensor" is there to detect situations where the suspension might bottom out and instantly switch to the hard mode - for example if you're going fast and hit a sudden rise or drop the sensor will detect this and the suspension will switch hard for a couple of seconds to prevent bottoming the suspension and also control the rebound.
The body roll is estimated based on steering wheel angle, velocity and road speed, the faster you go the less you have to turn the steering wheel away from straight ahead before it switches to hard. It also monitors the movement of the accelerator pedal so when you stamp on the accelerator it switches to hard to limit rear suspension squat. Heavy braking also triggers hard mode by way of the road speed sensor measuring deceleration. On the Series 1 it also switched to hard with a brake pressure switch triggered by more than 30 bars in the front brakes, but that was removed in Series 2.
The "normal/sport" mode switch does not directly put the car in soft or hard mode, gentle straight ahead cruising will always been in soft, hard cornering etc will always be in hard, what the switch does is control how "sensitive" the system is. In normal mode you can turn the steering wheel a fair way before it will switch to hard, meaning you tend to stay in soft unless you drive quite aggressively, in sport mode relatively small steering wheel movements will trigger hard and thus sharpen the feel of the cornering and tend to keep you in hard mode a lot more often. Likewise with the throttle sensor, in hard mode almost any small quick movement of the throttle will trigger hard, while in normal mode you have to stomp on the pedal for it to switch. (Other than acceleration from a standstill, where it always switches to hard for 3 seconds)
It changes a few other thresholds and logic decisions as well that aren't too important.
The suspension does some apparently strange things: When stationary, the front (only) sometimes goes to High/Intermediate (can't tell which) and stays there until the control lever is moved to Low and then back to Normal. I've thoroughly lubricated the whole height control linkage and done several rounds of Citaerobics to no avail - the front suspension goes up and down nice and smoothly.
This won't be anything to do with the Hydractive system it'll be the height corrector linkage. I'd check to see if the manual override adjustment is correctly in the centre of the slot.
Finally, I can't find the front supplementary sphere!
It's on a bracket down at the bottom of the radiator on the battery side of the car.
In front of the accumulator sphere roughly.
