Gold Sinker Mk1

[white exec]

Hi Graeme, and Mike

It's been a couple of years since I did the switch mod to the Hydractive II XM, to knock out the throttle sensor.
Reason for doing this was to make it possible to climb a very long (400m+) and steep, lumpy concrete hill - which required a good bit of varying heavy throttle action (which puts suspension into Firm) - without getting an unacceptably firm ride.

I didn't make any changes to the body movement sensor, and can see (agree with Mike) the risks in doing this, in allowing the suspension to forcibly reach its limits.

Since doing the mod (switch, relay and resistor - the last to substitute a fixed value in place of the throttle pot), I have realised that the cause of the unacceptable crashiness in Firm mode (firm mode just too firm, and transition to it too dramatic) was caused by the gas pressure in both rear corner spheres being lower than spec. This came as a surprise, as the spheres were both less than a year old, and correct genuine Citroen. Valved and re-gassed, the harsh Firm ride has disappeared, and remained that way for over a year. (I now fit valves even to new spheres, which facilitates a check.)

Graeme, what I think you could look at (if you haven't already) is the recent thread here on Xantia II revised Hydractive valves:
http://www.frenchcarforum.co.uk/forum/v ... 29#p494381
including the all-important Citroen service document in Marc's first post*.
Simon's (Mandrake's) analysis is very revealing, and might be able to provide substantial improvement to how your car (and mine!) handles speed bumps and the like, always an Achilles' heel.

I'm trying right now to acquire a couple of the new-type valves (Xan II, from RP8155 to end) to fit to the XM. Fitting them to a Xantia should be very straightforward.

* I had to open this in Internet Explorer.

[myglaren]

For those unfamiliar with them

[CitroJim]

^^ Also, those are Cockney rhyming-slang for something totally unconnected with steering

[white exec]

Only a matter of minutes now, before someone adds that smilie...

[CitroJim]

Only a matter of minutes now, before someone adds that smilie...

[aerodynamica]

hahahah what was I asking about again? I forgot! Anyway, thanks I haven't really been getting the notchiness in the steering, more a clonk at low speed heavy lock with change in camber i.e reaching the top of a ramp in a multi storey and turning. Checked the balljoints and track rods and they're fine. Bit of movement in the rubber bushes (though not as bad as I'd have thought ) so going to change them anyway.

I understand the caution of overriding the body movement sensor but I wonder how the 'forcibly reach its limits' of the suspension would differ from that on non-hydractive Xantia? surely there is nothing to prevent that on the non HA car and so it would hit the limits. There are bump and rebound stops for this. I might be misunderstanding the issue though. The Hydractive system has a greater volume of nitrogen in soft mode sure but the greater part of it is heavily damped (the corner, 'stiff' springs) so I'd have thought it would behave at least as well as non hydractive set up?

As an aside, my last (and most terrible) XM, a 1992 2.0 Turbo SEi had a problem in the Hydractive 1. I finally found that the speed sensor was faulted out and after a process it turned out that on higher spec XMs of the Hydractive 1 genre, the speed sensor sends its signal firstly to a black box in the dashboard that then seperates the signal to send a modified signal to the fuel/ trip computer and then a second output to the hydractive ECU. This was going wrong and the speed info was not getting read at the ECU so the hydractive thought the car was stationary when it was traveling. Apart from any other fault the repeated movement and hence, info from the accelerator pedal sensor was causing the ECU to go to safety mode i.e hard suspension. Basically, the suspension was always soft first thing in the morning or any trip, then after say, a minute of driving it would go hard and stay that way. It turns out that if the ECU gets repeated signals from a sensor such as the accelerator pedal but no speed input it faults out and I suppose it assumes the car is stationary and someone is revving the engine and so to stop the suspesnsion electrovalve constantly activating with the throttle, it 'sleeps' the system until speed info, i.e the car is moving again, is fed into the ECU. Since mine never was getting the speed info it always switched to hard mode and stayed there intil turning off and on again. What's the relevence? well after i found this was the problem, I disconnected (physically not umplugged) the accelerator sensor and the car started up in soft mode and stayed in soft mode constantly as there was no speed info and now no pedal movement info. Basically the ECU thought it was standing stationary with the engine idling. The car drove quite nicely, very soft as you'd expect with all 6 spheres engaged and although it was very soft, it still drove safely, never bottomed out overly heavy, took speed humps as would a CX, you know, like they're not there. and even drove reasonably well on the hilly and twisty backroads you get here if you look for them. So I'm not sure I'm too scared of the 'locked in softmode' suspension since I only need it for short, occasional but lengthy sections of speed hump roads. The speed sensor will still function so technically if the car is set to 'sport' mode but the bypass switch is set as well then it will have increased sensitivity to steering and brake pressure still. It will simply be that the input from the pedal and anti roll bar will be ignored.

Anyway, it's not an urgent job. I was out today and went over some fairly terrible local speed bumps. I've developed a technique of avoiding accelerator movements just before hitting the bump and it glided over almost CX like. It must be the overall height of the speed bump and the effect on the axle was less than the 80 or so mm needed to activate the hard spring setting.

Just thoughts above, Anyone have any cautionary thoughts on the switching out of the ECU (and hence switching to perma hard mode) of the system? This is after all the 'safe' mode as set up where faulted out components are detected. I can't see any real problem with having a Hydractive 1 style 'sport' mode so long as I remember to switch it back at the end of the journey to equilise the pressure in the spheres (probably the main reason HA1 had the system switch back to soft below 18mph)

The hydractive Xantia is among my favourite hydraulic Citroens (that I've driven) I just want to make it a little more excellent

[xantia_v6]

I understand the caution of overriding the body movement sensor but I wonder how the 'forcibly reach its limits' of the suspension would differ from that on non-hydractive Xantia? surely there is nothing to prevent that on the non HA car and so it would hit the limits. There are bump and rebound stops for this. I might be misunderstanding the issue though. The Hydractive system has a greater volume of nitrogen in soft mode sure but the greater part of it is heavily damped (the corner, 'stiff' springs) so I'd have thought it would behave at least as well as non hydractive set up?

A non-hydractive car has stiffer spring rate and damping than a hydractive car (in soft mode), and the spring rate is less linear (due to the smaller effective sphere volume), so by the time the suspension on a non-hydractive car has become fully compressed by a bump, it has already exerted considerably more upward force to the body, so the body is already rising, compared to a hydractive car, where the ride is essentially flat until the system switches into firm mode.

[aerodynamica]

Gotya, I agree about this but I just wonder if it's such an issue on 30mph or less urban roads.

It's funny because all the CXs I've owned; CX 2400 C-Matic x2, CX 2000 Reflex and CX 20 Pallas all quite happily slammed onto their bump stops on twist back roads without ill effect. I always wondered what it would be like to fit 400cc spheres to the CX, ideally of the right pressure, 75 bar front, but the best I had were 55bar BX fronts. I fitted these to the front of the CX 20 Pallas and went for a spin and found that the bump stops were rarey struck and the ride quality was still smooth albeit without the kind of disconnected float you get on the old school Citroens. It did however still roll as much as with the standard spheres so there was no improvement there.

I might still make the modification to the hydractive 2 but only after running the car for a day with the two sensors concerned disconnected to see the effect of this in the real world.

[white exec]

Mike is quite correct there.

Hydractive cars have far more "give" in the suspension when in Soft mode, and so will ride very flat (with a large vertical wheel excursion) when a speed bump is encountered. Locking the car into Soft mode is fine for moderate undulations (CX-like) - but would allow a potentially massive vertical wheel movement when meeting a large hump, causing the bump stops to be hit.

This is ok in theory and on a brand new car maybe, but if you look at the condition of bump stops on elderly Xantias and XMs, they tend to be somewhat tired, disintegrated, or even missing! The quality of these items isn't up to much, being rather fragile polyurethane foam, and something not to be brought into play with any regularity, I would have thought. XM and Xantia suspension is designed to operate against sphere gas pressure, not the stops.

A non-Hydractive car is sprung quite differently, as Mike describes, in particular the damping characteristics of the spheres. As he says, a sudden hump will cause upward body movement far more quickly and dramatically, thus limiting suspension squash. Comfort is sacrificed, compared to Hydractive.

Graeme - Any thoughts on the Xan II valve thread and technical paper?

[aerodynamica]

Hi Chris, I've yet to look at that - will report back in due course!

[aerodynamica]

Had a read of that again (I had read it previously) and simon's analysis is good but I don't think it would be easy enough to fit these later variants to an early Xantia without antisink (?) the different pipe unions notwithstanding. Shame though as it does sound like the ideal solution.

I might instead check the pressure regulator settings and add shims to the cut out/ in if needed. At least that way the supply pressure should be right.

[white exec]

On the thread changes, it appears that the difference is only in the female unions that screw into the valve body. I am assuming that the existing unions on the car's OE valves can simply be used instead, in order to match up with pipework.

The Citroen paper does include specific instructions for fitting these new valves to vehicles without anti-sink, so you should be ok there. The conversion effectively just involves deletion of a system supply pipe (6a and 6b), which the new internal drilling of the modified valve then provides, and this can be done whether car is anti-sink or not.

Simon also makes the point that the modified valve also makes the correct suspension action no longer influenced by a drift in system pressure. It does all look very interesting, and it's easy to miss bits (I did) on first reading.

[aerodynamica]

Just changed a ball joint and all better - in fact the lower wishbone bushings are all in good condition... I bought the full set and now don't need them (well if I'm being more honest the OSF P- bush rubbers ae begining to 'swell' a bit but no perishd rubber) I'll keep them in 'stock' for when they definitely do start to go.. Anyway, I now confirm that the rear trailing arm bearings are going so that's next on the list. I confirmed today that both arm-pushrod pins are free. I do this well in advance of arm bearing work after a dreadful experience of a stuch arm pin on a CX 10 years ago.. At least on the CX you can actually remove the arm and rear strut together with great care.. Anyway the ball joint was surprisingly straightforward even without the right Citroen tool but I was fortunate that the balljoint was not corroded in the hub carrier as that's a horrific job when it is..

You'd think after all this attention Old Katy would be happy but she's showing her thanks by continually giving me an electric shock on leaving the car. Why is this happening? I have new battery leads etc and no real sign of any electrical malfunctions. Is this caused by static build up or something maybe due to the larger ampliture vibrations from a diesel engine or something? I thought shocks from car bodies was a thing of the past and that was the reason for those old 70s/80s kind of earth trailing strap accessories people used to fit to the back of the car (?)

[Mandrake]

Just changed a ball joint and all better - in fact the lower wishbone bushings are all in good condition...

I haven't been keeping up with this thread, but what problem did you have that the balljoint solved, and was it the lower balljoint in the hub ?

You'd think after all this attention Old Katy would be happy but she's showing her thanks by continually giving me an electric shock on leaving the car. Why is this happening? I have new battery leads etc and no real sign of any electrical malfunctions. Is this caused by static build up or something maybe due to the larger ampliture vibrations from a diesel engine or something? I thought shocks from car bodies was a thing of the past and that was the reason for those old 70s/80s kind of earth trailing strap accessories people used to fit to the back of the car (?)

It will be an electrostatic discharge. What kind of seats and seat coverings do you have ?

My first S1 Xantia had fabric seats and it was a nightmare for shocks in the summer (especially on a dry hot NZ summer day) to the point that I just got used to firmly grasping and holding the metal corner of the door before I swung my legs out onto the ground, and maintained a grip on the door metal until I was standing. This gradually discharges the static charge without giving you a shock.

If I didn't do that I'd get a hell of a belt, almost every time.

My two Xantia's I've had since I moved to the UK have both had leather seats and the weather is not as hot and dry here so I haven't really had any shocks except for the rare one on an unusually hot day. Leather doesn't build up much charge compared to fabric.

[white exec]

Static build-up while in a car aggravated by all sorts of things - lack of humidity, seat coverings and clothing, cabin heating settings, choice of tyres (some are more conductive/grounding than others), choice of footwear, underwear . . .

I used to get a real 'belt' when getting out of the car and opening our steel driveway gates, especially in dry weather. Now make a point of touching the steel bodywork of the car first, and no more shocks.