V6 in Norfolk

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White Exec
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Orga / RP numbers: RP7165
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Re: V6 in Norfolk

Post by White Exec » Wed Jul 17, 2019 10:21 am

Hi John,

From the write-up of installing the Xantia valves in XM (October 2016)
viewtopic.php?f=7&t=8100&hilit=Evolution

" 10mm pipe connections
The Citroen working paper refers to the old ISO hydraulic union, and this being replaced from RP 8053 (25 March 1998) with a new CITROEN hydraulic union. The difference between the two is that the first type had a bell end to the 10mm pipe, while the second type featured a brass-and-rubber olive to make the 10mm pipe seal.
(The Citroen paper refers to notches on the new-type CITROEN unions; in practice, I found notches on both old and new unions.)
The new ‘internal pipework’ valves you have sourced could be of either type, but if you are going to fit a second type valve to earlier (ISO) 10mm pipework, or vice-versa, all that is necessary is to remove the large threaded unions (#14 in the diagram above) from your original valves, and screw them into the new ones. (The threads, internal and external, are identical, but the internal drilling is of a different depth and profile.) "
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DSCF2783-002.jpg
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I was making the point that the 10mm union design had changed, but if the XM's existing unions were fitted to the new Xantia blocks, the original XM joints would be preserved.

That gets over the issue of the changed 10mm pipes.
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Last edited by White Exec on Wed Jul 17, 2019 4:38 pm, edited 3 times in total.
Chris
1996 XM 2.5TD Exclusive RP7165 Polar White
2003 RAV4 D4D 2.0 5dr LHD Silver WORKHORSE
1989 BX19RD Delage Red Deceased; 1998 ZX 1.9D Avantage auto Triton Green Company car 1998-2001; 2001 Xantia 1.8i auto Wicked Red Company car 2001-2003

Dieselman
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Re: V6 in Norfolk

Post by Dieselman » Wed Jul 17, 2019 11:46 am

Having re-read the original thread on this topic, I note it says there is a spring to hold the shuttle valve in Soft mode, rather than the original design of system pressure.
The reason system pressure was used is to ensure the default is Hard mode, for safety.
Does this change mean the default is now Soft mode, in the event of hydraulic pressure loss?
If the system stays in Soft mode, it could render the car less stable in difficult conditions.
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xantia_v6
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Re: V6 in Norfolk

Post by xantia_v6 » Wed Jul 17, 2019 4:07 pm

No machining is needed to fit the late Xantia valve blocks, it is only necessary to transfer the damper valves and retaining adapters from the original XM valves.
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1997 Xantia Exclusive V6 (RHD) 45,000 miles

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White Exec
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Orga / RP numbers: RP7165
1996 2.5TD saloon, manual, Polar White
Location: ex-Ealing, Cheshire, W.Sussex & Surrey. Now living in Sayalonga (Malaga, Spain)

Re: V6 in Norfolk

Post by White Exec » Fri Jul 19, 2019 7:35 am

Dieselman wrote:
Wed Jul 17, 2019 11:46 am
Having re-read the original thread on this topic, I note it says there is a spring to hold the shuttle valve in Soft mode, rather than the original design of system pressure.
The reason system pressure was used is to ensure the default is Hard mode, for safety.
Does this change mean the default is now Soft mode, in the event of hydraulic pressure loss?
If the system stays in Soft mode, it could render the car less stable in difficult conditions.
Hi Will,

Have had a bit of discussion with Simon (Mandrake) on FCF about this scenario - i.e. when car is being driven, and main hydraulic system pressure were to be lost. This got me wondering about the new-type valve no longer immediately defaulting to Firm.

On the original valves, the suspension is held in Soft by system hydraulic pressure being higher than centre sphere pressure, and so if system pressure falls, the shuttle valve is immediately pushed into Firm.

On the revised-type valves, Simon said: "So the default position of the shuttle valve with the bias spring might be soft mode - but only when the electrovalve is actively held open under power from the ECU and is thus connecting both sides of the shuttle valve to each other. If the electrovalve is powered down it will default to hard mode as before as one end of the shuttle valve will be connected to the suspension pressure and the other to overflow return."

So in the event of hydraulic system pressure failing while driving, the regulators will continue operating normally, under instructions from the suspension ECU. This will include normal commands to temporarily switch to Firm, from all the usual sensors. A collapse of system pressure will throw up a warning/STOP message, and any unusual action by the driver ('difficult conditions' - sudden braking, avoidance, acceleration, body movement...) would bring on temporary Firm as normal.

Even though main system pressure might quickly collapse, the centre spheres would continue to exert hydraulic pressure, and operate the regulator blocks normally.

That's how we're reading it.
Chris
1996 XM 2.5TD Exclusive RP7165 Polar White
2003 RAV4 D4D 2.0 5dr LHD Silver WORKHORSE
1989 BX19RD Delage Red Deceased; 1998 ZX 1.9D Avantage auto Triton Green Company car 1998-2001; 2001 Xantia 1.8i auto Wicked Red Company car 2001-2003

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