Existential Xantia Question

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Gregg1100
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Existential Xantia Question

Post by Gregg1100 »

Hi,
Thanks for replies.
Will have a look tomorrow. I still think that it is all so un-necessarily complicated, and car will remain as it is until I sell it. As long as a car starts, goes , stops and is safe, then I am not bothered about the rest. I only bought it because it was in exceptional condition--see pic link below.
Greg

90 Kawa EN 500 A1- was running---now dead again
04 Kawa GPZ 500 E10 -alive and well.
54 Fiat Punto 1.2 Dynamic

Old Xantias- 16v 2litre 1997 VSX, 2 x 1993 TD Lx, S2 SX 1.9TD
Old Bx's--3 x 1.9 D, 1x 1.6 Auto, 1 x 1.9 GTi, 1 x 1.9 TZS
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Re: Existential Xantia Question

Post by HST »

andmcit wrote:
Gregg1100 wrote:Hi All,
I never said that Hydractive was any better or worse than standard. All I repeated was Citroens own words that in Sport mode, ride would be tightened up, --in Normal mode ride should be great. But you still have to switch between them, if you want one or the other, otherwise no point in having a switch. My Hydractive switch is permanently UP, UNLIT-OFF---so in Cits words, in Normal ride mode. Greg
You dont have to switch between the two options, possibly Citroen being 'clever' about what they've done with the suspension!!

In the normal "auto" option the car will electronically phase in and out of the TWO options [sport and auto], "sport" will ONLY give you the option with the corner spheres ONLY.

Could be your centre spheres ARE flat!! Try switching into sport and drive the car for a while and feel if there's any noticeable difference!

Andrew
Incorrect. Whichever position the button is in HA2 uses all the spheres, it just changes the criteria for when to switch to hard mode (i.e. isolate the centre spheres): it does not permanently engage hard mode. Drive down a straight bumpy road at constant speed and press the button. Nothing will appear to happen, the ride will be unaltered! The only differnce is that it will take less vigorous driving to engage hard mode automatically. You cannot select hard mode manually, only tell the computer to engage it more readily. HA1 differs, which may be the source of some confusion.
zxTd

Post by zxTd »

intelligent suspension is the name, used on top of the range mercedes and other marks and all derived from Citroen's ideas
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Mandrake
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Re: Existential Xantia Question

Post by Mandrake »

HST wrote: OK, here's an experiment for you. Find a bumpy road and drive along at a constant speed. Press the sport button. Notice a change in the ride? There won't be any. Hard mode will only engage if you brake, accelerate or corner hard. This is documented clearly in Citroens technical literature.
Actually there is another sensor - the "body movement sensor" which is attached to the front rollbar. If you hit a very large rise or dip in the road which causes either very large front suspension deflection, or very abrupt movement, it will switch momentarily to hard mode to control the rebound, and prevent the suspension bottoming at either end.

Going over a judder bump too fast, or going through a large dip in the road at open road speeds will trigger this sensor and to me anyway, the effect is quite obvious. It operates in both comfort and sport settings with very little change in thresholds.

I'm somewhat in two minds about the action of this sensor - on the one hand its good that if you hit something really sudden and large that it wont allow the suspension to bottom and rebound wildly, but on the other hand I feel its a bit too sensitive and sometimes activates when it shouldn't thus spoiling the ride quality unnecessarily...
Now find an empty roundabout and go round it 'briskly'. You'll notice very little if any roll with the switch in either position. The only difference it makes is how quickly the suspension switches from soft to hard and back again! The only time I engage sport is if I'm on a twisty road with a heavy load on the roof.
Not quite...there is no time delay in switching from soft to hard in either normal or sport, its always "as fast as it can" when a threshold is exceeded, which is claimed to be under 50ms, which is the operation time of the solenoid.

What changes in sport mode is that the thresholds for most sensors such as the steering wheel angle, are reduced by a factor of 1.5, and the time delay before going from hard back to soft again is multipled by 1.3.

So for example in the case of the steering wheel, it requires significantly less angle for a given road speed to trigger the hard mode, and it will take longer after straightening up before going back to soft, which is what makes the sport mode more suited to spirited driving on a windy road.

Maximum body roll is actually reduced in the sport mode compared to normal, but only by about 1 degree - from about 4 degrees to 3 degrees. The reason for this is that because it switches to hard "sooner" when you take a corner, less initial roll can take place before the roll stiffness is firmed up.

But if the car has *already* rolled a certain amount before switching to hard, as can be the case in the "normal" mode, then switching to hard can only minimize any further roll, it can't undo roll that already happened, unlike an Activa.
The system works so well you really can barely tell it's working: only the good ride and roll free handling give it away.

A further experiment. Brake to a stop with moderate to light decelleration and note how much the bonnet dips and then settles when you come to a halt. Now repeat with harder braking. The increased stiffness should be apparent if you stop quickly enough.

You may not think you are enjoying the effects of HA2, but if your car is working properly, you most definitely are, unless you drive at 30mph everywhere. If the hydractive spheres are shot your ride will be hard ALL the time. You can easily check if it is working properly: there are many threads about this.
Even something as simple as pressing the accelerator pedal moderately quickly when taking off triggers a switch to hard mode to minimize the squat at the rear suspension.

I've actually got my accelerator pedal sensor disconnected at the moment as I don't like that behaviour, I'd rather put up with a little bit of squat at the rear end and a smoother ride - like conventional Cit's :)

But you're quite right - people who think they're not getting the benefit of Hydractive 2 because they never push the sport button are misinformed. The computer is switching modes ALL the time as needed even for people that drive fairly sedately.

Bottom line is that the system allows the soft mode to be tuned for a very soft ride but not so that the car is dangerous to handle in extreme circumstances, because the computer knows when to disable the soft mode for safety/handling reasons...and you get the best of both worlds.

There is also another factor that gives the better ride of the Hydractive 2 - the interaction of the three spheres and two sets of damping valves gives a rather interesting property to the suspension -

The centre sphere, being shared by both sides in the soft mode, increases the softness of the suspension only for certain suspension movement "modes". (Not to be confused with hard/soft modes)

If you hit a single wheel bump, that bump gets absorbed by the sphere on that side, and the middle sphere, through two parallel paths. The centre sphere provides MAXIMUM additional softness in this condition.

If you then hit a bump that is equal on both sides, such as a judder bump, because both sides are moving together, they try to "share" the centre sphere, and it works out that from the point of view of each wheel, the additional springing provided by the centre sphere is HALF what it is for a single wheel bump.

Finally, in the condition of body roll or rocking, the centre sphere provides NO extra softness, because the pressure differences are opposite, all you get is a damped crossflow of oil and no contribution from the centre sphere.

What this means is that the centre sphere can make the ride softer with NO increase in body roll. It also means that it gives maximum effect on single wheel bumps and thus helps to improve the independant wheel ride - something which a rollbar works to worsen.

This means that the soft mode of Hydractive 2 can ride a lot softer than a standard model for the same amount of (or less) body roll - before it even switches to the hard mode.

The large volume but well damped crossflow possible in the soft mode also makes the car a lot softer against "warp mode" movements of the ground, thus keeping better ground contact on uneven surfaces.

Finally the Hydractive 2 soft mode gives 3 stage damping instead of conventional 2 stage damping. A normal damping valve in an outer sphere, which is all you have in a standard model, has 2 stages, and one threshold - there is one bypass hole of a given size, and one set of washers calibrated to a certain opening strength.

With Hydractive 2 soft mode there are two parallel paths for the oil to travel, both with different gas pressures, different bypass hole sizes, and different washer valve strengths. (The washer valves in the outer spheres are much stiffer than the ones in the middle)

Below the thresholds the oil only travels through the two bypass holes, but primarily towards the centre sphere as the holes are larger there.

Above threshold one the washer valves in the middle sphere will open, and above threshold 2 the washer valves in the outer spheres will open.

This gives more graduated, progressive damping than you would normally get...

Regards,
Simon
Simon

1997 Xantia S1 3.0 V6 Auto Exclusive in Silex Grey
2016 Nissan Leaf Tekna 30kWh in White

2011 Peugeot Ion Full Electric in Silver
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1978 CX 2400
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Post by DoubleChevron »

tomsheppard wrote:The correct answer is surely that it is there if you think that it is but if you cannot see it then it may not be there at all. :wink:
Actually, *my own* personal VSX is the only one I've ridden in that has good ride quality. The reason being I'm bloody certain the 'center spheres' are dead flat and full of fluid on most VSX car (XM's included). People tend to ignore the hyperactive spheres, yet these *are* your extra suspension dampening. Without them fully charged you have hard mode ... and hard mode ie: NO soft mode.

Next time I see the guy one of the guys here in Ballarat, I'm going to force him to run his Xantia up on the ramps in my shed. His VSX rides like cr@p, and the "Citroen Specialists" (I used that term very loosely) that he purchased the Xantia from have assured him the spheres are all fine :roll: :roll: Yet it rides like my car did with flat hyperactive spheres ... ie: much WORSE than a VSX.

seeya,
Shane L.
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and of course, lots of old Citroens, slowly rusting away in pieces ;)
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Re: Existential Xantia Question

Post by DoubleChevron »

Gregg1100 wrote:Hi,
Thanks for replies.
Will have a look tomorrow. I still think that it is all so un-necessarily complicated, and car will remain as it is until I sell it. As long as a car starts, goes , stops and is safe, then I am not bothered about the rest. I only bought it because it was in exceptional condition--see pic link below.
Greg
Remember the CX, GS and DS (all of which I have here). The Xantia VSX's bum should be SOFTER than all of these. You should be able to effortlessly push it's back suspension down to it's bump stops with two fingers.... It's THAT SOFT. If it's not your h/a *and* possibly the wheel spheres are flat.

The front will still feel firm without a lot of give. this is normal, however it's the rear of car that give the vastly better ride (IMO).

As a test do you have any spare gassed accumulators there ?? Possbily pinch some gassed accumulators from you BX's and fit them to the Xantias center spheres (after all they are only accumulators with a slightly different pressure).

The Xantia hyperactive is the closest you'll get to *proper* Citroen ride quality (ie: CX, GS, DS, SM) in a modern car.

seeya,
Shane L.
'96 Big BX 2.1TD exclusive slugomatic (aka XM)
'85 CX2500 GTi Turbo Series II (whoo hooo)
'96 Xantia VSX slugomatic (sold !!)
and of course, lots of old Citroens, slowly rusting away in pieces ;)
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Re: Existential Xantia Question

Post by Mandrake »

DoubleChevron wrote:Remember the CX, GS and DS (all of which I have here). The Xantia VSX's bum should be SOFTER than all of these. You should be able to effortlessly push it's back suspension down to it's bump stops with two fingers.... It's THAT SOFT. If it's not your h/a *and* possibly the wheel spheres are flat.
Yep, mine is/was like that too. In fact I find the back a bit too soft, so yesterday when I had the rear hydractive valve unit out for a good clean I reduced the damper bypass holes in the central damper valves from 1.1mm to 0.9mm to firm the rebound damping slightly in the soft mode.

So far I'm impressed... the slightly underdamped floaty feeling has gone from the back, but with seemingly no loss of ride quality. It's pretty close to critical damping now - well controlled rebound with no overshoot.
The front will still feel firm without a lot of give. this is normal, however it's the rear of car that give the vastly better ride (IMO).
Yes the back is also very important for the ride. Mine came with the rear centre hydractive sphere punctured and the difference in overall ride quality in the front seats of the car when I replaced that sphere was stagering.
As a test do you have any spare gassed accumulators there ?? Possbily pinch some gassed accumulators from you BX's and fit them to the Xantias center spheres (after all they are only accumulators with a slightly different pressure).
Good as a test, but too soft IMHO for long term use. I ran mine with an actual acummulator sphere there for a week or two while I waited for a suitable replacement, and the ride was very smooth, but boy was it too soft at the back for handling :)
The Xantia hyperactive is the closest you'll get to *proper* Citroen ride quality (ie: CX, GS, DS, SM) in a modern car.
I'll believe that if and when I get my front strut issues sorted out.... :( I hope you're right...

Regards,
Simon
Simon

1997 Xantia S1 3.0 V6 Auto Exclusive in Silex Grey
2016 Nissan Leaf Tekna 30kWh in White

2011 Peugeot Ion Full Electric in Silver
1977 G Special 1129cc LHD
1978 CX 2400
1997 Xantia S1 2.0i Auto VSX
1998 Xantia S2 3.0 V6 Auto Exclusive
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Existential Xantia Question

Post by Gregg1100 »

Hi All,
Two things have come about since I answered a post here today.
1st. That you are a great knowledgable bunch of helpful people that one could ever wish to meet.
2nd. My Xantia will shortly be going up for sale. Because I have not the time or money to spend to get a magic carpet ride.
I only need a car for 10 miles a day-to work at 05.00 and home again. I will get my Volvo back on road. No Abs, no cats in sight, a damper and spring in each corner. Easy street.
I may look out for another Xant, later on,---but with a TD engine and only Lx spec--less to go wrong. I will post it in this forum when ready. See pic of car in links underneath this post end.
Besides which, I need the money to get house roof fixed.
Greg

90 Kawa EN 500 A1- was running---now dead again
04 Kawa GPZ 500 E10 -alive and well.
54 Fiat Punto 1.2 Dynamic

Old Xantias- 16v 2litre 1997 VSX, 2 x 1993 TD Lx, S2 SX 1.9TD
Old Bx's--3 x 1.9 D, 1x 1.6 Auto, 1 x 1.9 GTi, 1 x 1.9 TZS
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Re: Existential Xantia Question

Post by HST »

Mandrake wrote: Not quite...there is no time delay in switching from soft to hard in either normal or sport, its always "as fast as it can" when a threshold is exceeded, which is claimed to be under 50ms, which is the operation time of the solenoid.
I know, I wasn't being totally clear. What I meant was how soon it chooses to switch modes not the speed of the actual change. I was avoiding to much detail as people can start to get a little lost.

I suspect my centre spheres may be on the way out as, though fairly smooth, I don't think it's as soft as others are describing. Hard mode in my car is so roll free it makes me wonder why bother with Activa for sane road driving. I suspect Citroen feel the same.
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