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

Hi George, the body sensor - if my facts are right - will trigger the processor when either a displacement of 60mm occurs 3 times or more per second or a rate of change of 0.3mm per millisecond. The hold-off time is 0.4s - unless another change occurs (steering sensor etc) - plus the 0.1s for re-energising the valves, so all in all 1/2sec to switch back to normal mode, hence on broken surfaces the body sensor will likely continue to re- trigger well before the changeover time, holding the valves de-energised.To put the timescale into perspective the blink of an eye takes 15m/s!I think the the problem we are all stuggling with and trying to define is, is the suspension in the right mode? As an aside, i've read somewhere that replacing the hydractive sphere with an accumulator sphere there is an improvement to be had in comfort without detriment to overall performance of the hydractive system.

Hi Robert

So your hypothesis would be on the "rate of change of 0.3mm per millisecond" induced by rough/saggy tarmac, right? On Monday I ll drive the XM again and see if it goes in "hard" over those surfaces.

Don't know about the accu sphere in place of hydractive, could be, as they are similar, however odds show the accu sphere will be "harder" than a standard middle sphere for the front:

accu:
400cm, 62 bar

hydractives, front:
450, 75bar
or
500, 70 bar (depending on year)

At the rear an accu sphere would give a much softer feeling -too much perhaps- as it is same volume -for hatches, estates have 500cc- but much higher pressure, 62 vs 30 or 40bar (can't remember exactly).

Why experiment though since the car can be perfect if all gets to work like it was designed to...

E.g. I often wonder why Cit have specified the accu sphere to be *exactly* 62 bars (why not...60?) for all their models since hydropneumatics exist, well this must be the optimal for some reason...

cheers
George

Hi George,

Ref the accumulator pressure. Without doing the sums I would guess it's for the same reason that aircraft hydraulic accumulators always have air charging pressure of half the system pressure - it gives the maximum volume displacement between cut-out and cut-in of the control vave.

Derek

This post has been edited by DerekW on April 05, 2008 07:09 pm

Hi Derek

...makes sense, yeah. Putting the numbers down (145-170) it shows the accu sphere diaphragm would move in a range between a little above 50% and less that 70%, sounds ideal.

cheers
G

Sorry to hear you've got the 'lergy Dan, looks like you might get some snow tomorrow too. Stay in and warm, or get some fresh air or something! Just saw beeb forecast, if its any good then snow will miss me and I'll get to do the mirror and the hoovering on mine.

regards

Hi Tim and all

Wow snow!!!!! i couldnt resist it today, went for walk with the mrs over the downs this morning, its so pretty in the snow, even when your snotty and red nosed .
Back to the subject at hand anyway, Why substitute spheres?? i dont think this is a good idea, the system would have worked well when new, so if there is any problem with ride quality it would be down to system dirtying, leakage, wear or electrical failure, there can be no other reason and i would say if you want the car to do what it was designed to do it is best to rectify the problem rather than cover it up.

D

Good evening all,

OK, it is definitive, I have arrived at the end of my trip -and a new one, the good one, starts NOW!-

I have driven today the car again, it's been 2 weeks since putting fresh LHM and 3rd time I drive it since. It needed some time to settle down -as always wit hhydraulics, we are not newbies now, are we -. As of today, it is like that one day of March 2006, when tunning the pressure regulator magically opened up the hydractive pistons for the 1st time in my ownership. SILK. Rounds everything. Struts "reading" the road. You only get an *impression* of what u pass over -you only know what it is because u also pass it with other cars-. No rumblings. No crashes. Tyres pressures as on the door sticker (checked today). Just, "roundness". Great.

All that is not there is just the 20% pressure missing on my spheres at the moment (measured). Actually I'd say it doesn't make any perceivable difference, just that it is a fact that I'm aware of.

*Exactly* 6,000 miles on hydraflush did this -with a Hydronet mix towards the end-, and 10 to 30 ups/downs each day I used the car. And some slaloming at the end. I suspect someone driving on curvy roads would have got the result quicker -I'm doing borring motorway 90% of my miles-.

So, it is now confirmed: if you have checked OK all else in your XM and still it is "not-so-soft"; I repeat, ALL ELSE, then it could just be that dirt made your struts sticky. Just that.

Also confirmed: pressure regulator cycling time doesn't matter: mine was absolutely same soft when, at days, it was even cycling as frequently as each 10 secs. If the pressure range is sufficient (cut in 145-cut out 170bar), it seems the hydractive pistons can remain well opened up. My car is not any pressure-keeping champion, it clicks at 20-28 seconds intervals, which is "fair".

I remind that this is a 170,000 miles 3lt XM DIRAVI that I have received with flat spheres and freshly changed LHM, at 138,000. Hydraulics and electronics have all been checked, measured, and fixed. The only repairs the car needed were

2x diodes,

spheres, and

pressure regulator re-tuned to 145-170 bar.


YOO-HOOOOOOOOO!!!!!


cheers
George

ps. anybody wants 3 brand new strut cylinders and 2 height correctors out of the box?? (just joking)

This post has been edited by jorgy9 on April 09, 2008 04:25 pm

Not to leave any questions, I also have to add:

1/ Yes, the suspension has become softer with the fresh LHM than it was with the 6,000 miles-old hydraflush mix. There were still occassions when it would be "crashy" on hydraflush, still some "spikes" in the operation, if u see what I mean. This totally dissapeared with fresh LHM -it's as if everything has been perfectly lubed now-. This would go against theories that because hydraflush is thinner than LHM it will give a less damped, more comfortable suspension. PErhaps this is the case when you add hydraflush in a car-in-need, so in the beginning of the process it will naturally free up the suspension. But after it does that job, it just looks like LHM is by far the perfect formulation for the design. The LHM-effect is weird, not easily described; it's like hydraflush had made it a "very soft suspension" and LHM has made it a "Citroen suspension", where you don't feel anything. And in the same time it feels more controlled at any moment -but you can now also feel a clear, slow, wallowing on the motorway, over the appropriate obstacles, totally a-la-Citroen!

2/ I did not change hydraflush at all over these 6,000 miles. Only have been adding about 1lt of extra oils (LHM, Hydronet) on the way, because mine was getting lower due to a slow leak -that I still have not cared to find-. So it seems hydraflush is easily up to such a task.

3/ I've been a very naughty boy and have not even cleaned at all the LHM tank filters this 6,000 miles- not even now that I've put fresh LHM in-. Still don't know how they look like dirtiness-wise. In May though I'll open everything and clean up.

There you go, some...unorthodox variations in the practice that perhaps prove what is essential and what not.

cheers
George

Can we all quote you on this in 6 months time?

Hope so.

Fingers crossed!!!!

I recently did the sit in the boot thing and it worked, but it was oh so sloooowww! At first I didn't think it was going to work but eventually it did.

You mean with engine running, or off?

G

Off. Had been running then I stopped it and sat in the boot.

That's great then, you have a good presure reserve.

Mine cannot do it with engine off -it used to be able to, before this event of March 2006-. My regulator clicks @ 14secs, was longer before that day. So my low/high pressures are right, but they get wasted through something that got shot on that day.

They HAVE to be able to do it normally.

G

Yes I changed all the spheres apart from the rear wheels, still haven't done them.

I'm coming round to your way of thinking George, maybe I haven't got enough pump pressure due to the regulator being low.
I think the rear "drop" thing after driving a mile or so could possibly be the e valve struggling to open due to low pressure?