Is there

rossnunn · Post by **rossnunn** » 01 Jul 2006, 23:21

any way of setting the standard ride heigh of a xantia lower & no loose the raise & fall of the system using the leaver?
I have a mad idea to retro fit the activa system on a kit car, but it needs to be lower.

Mandrake · Post by **Mandrake** » 01 Jul 2006, 23:28

rossnunn wrote:any way of setting the standard ride heigh of a xantia lower & no loose the raise & fall of the system using the leaver?
I have a mad idea to retro fit the activa system on a kit car, but it needs to be lower.

Browse back through the forum a few days as this exact question has just been discussed in length....

Regards,
Simon

jeremy · Post by **jeremy** » 02 Jul 2006, 09:58

Its all regulated by the linkage to the height corrector - so if you're making a kit you have full scope.

The difference between AIR suspension as fitted to Range Rovers and other cars and hydropneumatic as fitted by Citroen is that the height with air suspension is controlled by the pressure in the air bags. With hydropneumatic the height is controlled by the AMOUNT of the LHM (which is of course incompresible) not its pressure.

deian · Post by **deian** » 02 Jul 2006, 11:38

So if the height is controlled by the fluid, why does the hydropneumatic suspension not bounce when on full height (assuming the nitrogen is still pushing compressible)? Is it because the LHM compresses the nitrogen in the sphere's making it incompressible?

I think it would be a great idea if citroen continued with the hydractive suspension, and have a nitrogen canister to keep the nitrogen in the spheres topped up or to have it increased, so the lhm can lift the car, but you could also pump in more nitrogen for to increase bouancy at height.

Or maybe someone could do this kind of idea? Connect pipes to the recharging valves of the spheres with nitrogen in a canister?

AndersDK · Post by **AndersDK** » 02 Jul 2006, 12:45

Deian have a look on this site, not too much text - very easy to understand :
http://web.actwin.com/toaph/citroen/work/work.html

Note that LHM is a fluid - and can never ever be compressed.
Nitrogen is a gas - HIGHLY compressable and flexible.

Any gas works as a coiled spring : the harder its compressed - the less soft it feels in a suspension. Thus you can apply the spring constant to gas spheres - calculating on suspension setups and softness.
(Though at some very high pressure point the gas is finally compressed to a fluid)

deian · Post by **deian** » 02 Jul 2006, 13:13

so you can't just pump in more nitrogen into the sphere to make it spring more at full height? thats my idea you see, i understand how it works (maybe my words weren't choosen well)

i understand it's the lhm that controls the height and transfers the forces around the car for stability and the nitrogen is like the spring, i also understand that gas is compressible and liquid isn't but does act as a perfect medium to transfer forces (hydraulics) as it doesn't compress but fills any shaped volume, therefore distance or shape isn't an issue.

AndersDK · Post by **AndersDK** » 02 Jul 2006, 14:28

deian wrote:so you can't just pump in more nitrogen into the sphere to make it spring more at full height? thats my idea you see, i understand how it works (maybe my words weren't choosen well)

i understand it's the lhm that controls the height and transfers the forces around the car for stability and the nitrogen is like the spring, i also understand that gas is compressible and liquid isn't but does act as a perfect medium to transfer forces (hydraulics) as it doesn't compress but fills any shaped volume, therefore distance or shape isn't an issue.

And I guess thats why you have the ideas fitting a hydraulic system to a kit car - or a BMW.
As you are right : its a lot more versatile and easy to adapt the hydraulic system - than any mechanical rods/spring system.

Basically you fit the active components - then find a suitable route for the piping - and you're done 8)

vanny · Post by **vanny** » 02 Jul 2006, 16:33

will the weight of 8+ spheres, control unit, ecu, piping, regulators, HC's HP pump and all the other gubbins not reduce the benefit against springs?

I've looked into this recently and i figured it would add anything upto 50% extra weight onto the car im building, however i only have a 600cc engine and need the weight under 400kg to be competetive!

deian · Post by **deian** » 02 Jul 2006, 16:45

Precisely AndersDK, such a cool idea yea.

Vanny: up to 50%! I seriously doubt that, unless you were adding it to a mini or something. I was thinking of adding it to a 170bhp 2.5 BMW, i doubt it will make much of a difference in terms of power/weight.

vanny · Post by **vanny** » 02 Jul 2006, 16:58

well the activa rams weigh a good 15kg each so theres 60kg before anything else, pump is a good few kg and before you know it it starts to really add up!

Bear in mind this is a tiny weeny 1 seater that proably wont get much above 70mph! Can't remember the specs for the first design, but the current winning team have a car that is only a little over 360kg! Doors on a CX weigh almost that much each

I'm looking at trying to fit it to a BX, and i think the biggest problem is doing to be room to fit all the various bits in especially all the extra spheres, thinking that the only way to go with them is in stead of the spare tyre?

jeremy · Post by **jeremy** » 02 Jul 2006, 20:42

You're right - compressing the nitrogen gas in the sphere does make a Citroen bounce. This is why there is a damper valve in the neck of the sphere - and why accumulators which have no dampers must never be fiitted to struts.

rossnunn · Post by **rossnunn** » 03 Jul 2006, 22:55

vanny weight won't be the problem as it would be producing 250+ bhp.

rossnunn · Post by **rossnunn** » 28 Jul 2006, 00:25

the old man has come up with a nice simple & cheap solution, cut more slots in the slider inside the car. will run it lower & a little stiffer without being rock hard.

Mandrake · Post by **Mandrake** » 28 Jul 2006, 00:34

vanny wrote:well the activa rams weigh a good 15kg each so theres 60kg before anything else, pump is a good few kg and before you know it it starts to really add up!

15x2 = 30 ??

Or did you think there were 4 Activa rams in an Activa

Regards,
Simon

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