Damper and sphere sizes

[marc61]

Hi

Would anyone have the XM corner and centre sphere sizes in cc's and the damper hole sizes for the corner spheres and for the hydractive valves? Also what's the logic in changing damper hole sizes on the front corner spheres of different XM models - does it relate mainly to engine weight differences?

I'm playing again with the hydractive valve I fitted to front end of my DS and would appreciate above info if anyone has it.

Thanks

Marc

[Andmcit]

this link downloads the aswas andyspares sphere table:

http://www.attfield.dircon.co.uk/sphere_table.pdf

TBH, I've no idea who's site it's attached to although the following
Activa spheres table is Jim's from FCF:

http://www.eastment.net/forum/activaspheres.pdf

trust this shows you the sphere volumes/jets and pressure options to suite your experiments!
The Xantiae spheres (whilst very similar to the Xm hydractive ones) do offer some alternatives.

Andrew

[marc61]

Thanks Andrew that's really useful.

I see damper size went down on front spheres from 0.7 to 0.6mm and pressure from 55 to 50 bar for models with heavier engine. I wonder if they changed the damper sizes in the hydractive valve for the centre sphere too? I've only collected selection of dampers from XM 2.5 hydractive valves and all look same size holes but I don't trust my eyesight and cant measure holes that small. They've got what looks like 0.4 and 4.6 engraved crudely on them - does that correspond to rear and front hydractive valves I wonder?

Happy to share experience of running DS with hydractive front end if it's of interest to anyone.

Cheers

Marc

[eduFX]

Hi...somo pictures...

To the front..hole 5 - 1



To the rear...hole 3 - 2



Rear central Hidractive...



Front central Hidractive (green)...big metalic hole!!



eduFX

[xmexclusive]

Hi Marc

I bought a cheap set of fine metric drills to use to check damper hole sizes.
20 drills - 0.3mm to 1.6mm from Machinemart cost £4.69

www.machinemart.co.uk order code 060238304.

John

[robertmnorton]

Hi Marc,if you have access to the citroen service website you can download the mechanics handbook for any model(well almost) which includes the sphere and h/a valve configurations.If not i've uploaded the xm/xantia one here.It may be of interest to download the c5 as well.The c6 has variable damper suspension cylinders,so no use for comparisons.
robertm

This post has been edited by robertmnorton on April 29, 2011 12:14 pm

[marc61]

Thanks gentlemen thats useful info, much appreciated. I've now measured the damper holes in front and rear hydractive valves from my old 2.5 and can confirm that what the book says is correct, 1.25mm holes both sides both axles. I don't know what the 04 engraved on the dampers means any more than the similar marks on the sphere photos from eduFX. What does strike me is how marked the differences are between the HA damper size and the corner sphere damper size - when the centre sphere is in circuit it's doing a lot of the absorbing, and when out of circuit the "springing" provided by the corner sphere really is very different. No wonder we complain if the electrovalves aren't working!

On a conventional hydropneumatic Citroen when turning a corner or a sharp bend a bit too fast, there is nothing to stop LHM transferring from one front cylinder to the other and this accentuates roll - one cylinder compresses, the other expands and fluid rushes across. Then along comes the XM and its a revelation, well maybe not but after several years its arguably a bit better than what went before! So I've been interested in whether an older Citroen can be improved, hydraulically (i.e. minus the XMs electronics).

At various times I've plumbed the HA valve on the front suspension of my DS in both modes, with centre sphere permanently in or out of circuit. Where the large diameter hydraulic pipe on the XM screws into the HA valve is an adaptor below which is the centre sphere damper (one each side). What I did was make exact copy replacement adaptors except they have M9 holes to take 4.5mm pipe so that standard pipes can be used to connect to each front suspension cylinder. This provides the equivalent of XM hard mode in that the HA valve stops cross wise flow of LHM between the spheres. It cuts the amount of roll by a huge amount on a DS! Have done about 15,000 miles like this without any problems. Id do this on a CX if I still had one but there we go. The only disadvantage I've found is the car is slower to rise at the front from a cold start due to the restrictive passageways of the HA valve. Im thinking about putting an anti-sink valve on the front to compensate.

The other way I've done it is with the centre sphere permanently in circuit. I unscrewed the shiny electrovalve assembly from the HA valve and made an M18x 1.0 plug to fit instead and used a Dowty washer. That's the equivalent of putting an XM in permanent soft mode. On the D it's supersoft, but you still get the anti roll benefits of having the HA valve on board. In this mode with the right corner sphere volumes and dampers I reckon there's an optimum to be found, without resorting to electronics.

So the HA valve from a Mk2 XM is a very useful thing if you drive older Citroens too. I'm in the process of doing a spreadsheet to understand how the spring rates and suspension frequencies vary across the big Citroens of old. I can see it's very sensitive to damper size, sphere volume, front end weight and whether an HA valve is on board. If anyone has the front and rear weight values for XMs, CXs and the D would much appreciate the info.

Cheers

Marc