Hydraflush And "hydronet 2000", ...and the happy ending of an Odyssey!

Guys, check out the new link at my signature, a 2.5td year 2000 from a member of planete-citroen...almost gave me seasickness, so wallowy it is!!!

Ok, in summer I'll seriously deal with my suspension's issues. Mine perhaps has a similar travel but the freedom of moving is definitely not there.

cheers
G

This post has been edited by jorgy9 on April 02, 2008 05:15 pm

I resemble that remark If you saw my post re suspension problems on mine, you may have noticed a sure fire way to tell if the electrovalves are working or not, the fact that you can hear the buzzing, or it's really a whine, 1000hz, doesn't necessaraly mean they are open. You should hear a definite 'clonk' as they open, followed by the whine, and the another 'clonk' as they shut, about a minute after closing the door or whatever. Mine were clonking when the door was opened and they switched on, but not when they switched off, so no soft suspension as they were actually closing almost immediatly after they opened - reason? defective diodes in the solonoids.

Right, I will go back to sleep now.

Peter.N.

Was that XM fitted with comfort spheres do you think?

Steve.

Not as far as I know, I'll ask the guy. He got it right with the help of the other guy whose car in on the first video.
G

Very interesting. Does the first guy say how he fixed his?

Steve.

As far as I remember they both had pretty standard problems, eg diodes, spheres etc, not even something presssure-related. They both have run Hydronet which -they swear- brought the final blow to the stifness. In my car all this and more has been done and it's a mystery why the susp it's not performing like theirs -a "mystery" I say, anyway there's nothing mystirious, just something I've not found yet-. At the end I'll start replacing parts with new till it performs -what I'll do before, in summer, is check the return pipes one by one, I've been postponing it for ever-. On the other hand, my steering is today, with fresh LHM, better than it has ever been, like new I imagine, so this shows it's a localised suspension-related problem.

Personally I estimate in most of your XMs that don't go well, having repaiered all other things, it will be the low pressure effect (regulator), this is what instanltly fixed mine which is far older&worn than most S2s here, now, what hapenned to mine the day I bled the brakes, *this* is the "mystery", but hopefully none of you will have anything similar.
G

This post has been edited by jorgy9 on April 02, 2008 09:56 pm

Evening all
I'd just like to say how absolutely fascinating it is reading this and the other threads running on the hydraulic forum. It's really absorbing following these discussions and then listening out for all the pops, clicks and hissing when I'm playing about with my XM. I'm pretty sure there's a couple of spheres that could do with being replaced but even so it's still the most comfortable car I've ever owned. Anyway, carry on

Bob

Lucky you Bob!

G

Ok, so this guy with tehe grey 2.5td XM has answered that his corner spheres are from Citroen and his middle are IFHS. So, no, it's not comfort spheres....It's not even my spheres -which must be AMTEX or something- as they gave an amazing ride a couple of years back -and the front ones still give a good ride-. Just my rear suspension having something else. I should check the rear spheres though, who knows perhaps one has exploded -although this would be very obvious when car passes momentarily in hard, the car becomes like a cangoroo, had this with one front sphere-. Plus it's extra soft in other occasions, e.g. it crashes the rear when starting from a traffic light. So no, the volume is there. Something else doesn't allow the cylinders to move fast enough. Perhaps I should start thinking of rear arm bearings, although again they've been perfect 2 years ago and no sign now of them being worn -noises etc-.
G

George - if your car squats when you take off from traffic lights then that seems like your rear electrovalve is not closing properly when you plant your foot on the accelerator?


My understanding is that the only differences between comfort spheres and normal spheres is the internal nitrogen pressure - comfort spheres are higher pressure.

f you had the luxury of a sphere charging rig (I haven't ) I suppose you could make your spheres to any specification between normal and really soft by just varying the sphere pressure. Is this too simplistic and am I missing something?, perhaps Noz & Co could comment.

I know it's not big and probably not clever (time will tell), but the ride on both my driveable cars is super soft at the moment, with the hard mode coming in noticeably and as normal. The saloon has a mixture of aircraft hyd fluid (80%) petrol (10%) white spirit (10%). The estate has ac hyd fluid (85%) petrol (15%). I cleaned the filters again last night and loads more black silt had been deposited in the reservoirs. I'll continue with these mixtures until either the summer or until the silt deposits decrease.

Yes, every residential street has one........I'm that bloke who tinkers with cars and always has his bonnets up!! Perhaps it's 'cos I don't care much for TV ball sports, alcohol or gardening - I find enjoyment in just tinkering.

Both hyd systems appear healthy judging by the tiny amount of fluid in the return pipes and my cars bounce like the french car in George's youtube video links.

"My understanding is that the only differences between comfort spheres and normal spheres is the internal nitrogen pressure - comfort spheres are higher pressure".

Not quite, comfort spheres also have a larger orifice so as to reduce the damping stiffness.

Peter.N.

I drilled out the orifice in an old pair of Xantia spheres as an experiment. It certainly made the car softer. However you can't alter the flap valves as far as I know. Or have I got the wrong end of the stick here?

Does anyone have a definitive explanation of the sphere valving/damping operation?

Steve.

Not exactly. Each sphere is inflated to a static pressure, and then when LHM is pumped as the car goes up, the sphere will be further pressurised. It will be pressurised exactly up to the pressure that each wheel receives because of the car's weight. Ok , that's not exact for hydractive cars as they have 3 spheres/axis. So these 3 spheres will be equally pressurised when the car is up and steady. If a sphere is e.g. 40bars static pressure, then for an XM it could go to 70 bars perhaps. For a lighter car it woudl go to less than 70 bars, car steady and in normal drive height. I guess calculations from kilos to bars should be possible, but cannot do it myself (a task for Derek?). But if we wanted we could calculate to how many bars a sphere on a car will be pressurised at, when car is steady.

The bottomline is that the static pressure of a sphere is precalculated taking into account the weight of the car it is going to be on, so as to the sphere's diaphragm to be more or less in the middle position when the car comes up and is steady. This will give more or less an equal travel of the suspension to both directions.

If you take a sphere that has been specified for a car and inflate it more (higher static pressure) this sphere will give greated comfort on compression of the wheel (there will be a greater upward travel available and pressure in sphere (=suspension hardening) will rise less quickly for each cm movement of the wheel). But you will have the opposite effect at the extension direction, ie for holes. Not to mention adverse effects when cornering. Further, all the above is only valid in a car where each sphere serves each wheel, and the spheres don't communicate with each other. In the Cit layout of the system each axis is united, so this makes it even more complex to calculate what the effects will be -not impossible at all, just difficult with the human mind-.

So, if you wanted a softer suspension the indicated paths are two: 1/less damping, 2/put a larger volume sphere, again with its static pressure appropriately calculated as to the diaphragm to be in the middle when car is "in position". That's not difficult to find, I had done an Excel some time ago where I was comparing the effects of different pressures and volume combinations. I should post it sometime soon but it needs a good narrative which I don't have time to write now. This option will simply make your car indulate pretty much uncontrollably (assuming equal damping with standard sphere) as the suspension travel will be greater, suspension bottoming out easily etc. You would need really carefully calculated alterations to achieve a real good compromise -e.g. don't even think of putting 500cc corners on an XM-. XM's have a posibility at the front as there's been a 450cc sphere for the V6 for some period, but then I guess this would have been more damped, even more so for the needs of a 2lt car, so you gain some, you loose some. If you really want something softer and you have e.g. a 2lt Turbo, you can try the simple 2lt front corner spheres, which are same pressure&volume, but -I assume- less damped -so will give you exactly what you need-.

If you want more wallowing you could try drilling the middle orifice in 0.1mm steps -each 0.1mm really make a difference-. I had comfort spheres with about 0.9mm (when standard V6 is about 0.5) and it was wallowy like a CX (but not pleasant at all in cornering, most vague car I'd driven -and my father had a Volvo!-).

Overall the XM doesn't need comfort spheres if it works as it should. Plus, with Hydractives, there's a lock: with the front sensor for antiroll bar movement, the XM's wheels are limited to a specific speed of travelling up/down. If you fit seriously un-dampened spheres, the car will be entering hard more much more often, if u see what I mean, thus you'll be loosing your precious middle sphere...

cheers
George

No, it squats with easy take-offs, if u thrash it hard mode enters and it doens't move at all. Precisely, I shoudl say it USED to squat and crash and bottom out the rear easily with the hydraflush, now with fresh LHM there's a distinct increase in damping rate.

cheers
G

That's great news, glad for you, hope it's definitive!! Let's see how it goes, I might try it too in summer.
G