C6 on Top Gear (in uk only) Sunday 4th June

Richard Gallagher · Post by **Richard Gallagher** » 05 Jun 2006, 22:54

Try the following link for the video http://parkeerplaats.citrofiel.net/Top% ... 6_2006.mpg Hopefully it works outside of the UK as well

wheeler · Post by **wheeler** » 05 Jun 2006, 23:51

Mandrake wrote:
wheeler wrote:
Kowalski wrote:
Is there anything to say that the 4 spheres on the "rear axle" are all ride related though ?

Perhaps the 4th does some other function - like the anti-sink sphere on a Xantia...which is connected to the suspension, but doesn't actually affect the ride.

If there were 4 directly associated with controling the ride, I would have thought they'd use 4 at the front as well...

at the rear there is one for each strut & the other 2 are for stiffness regulation,on the front there is only one for stiffness regulation

bxbodger · Post by **bxbodger** » 06 Jun 2006, 00:09

The reality is that it'll be down to the beancounters what the business user gets and its going to be German every time.

The C6 is just too expensive to take a risk on when there's doubt about its resale value already, and nobody wants something that'll plummet faster than an Omega......

Mandrake · Post by **Mandrake** » 06 Jun 2006, 08:11

Richard Gallagher wrote:Try the following link for the video http://parkeerplaats.citrofiel.net/Top% ... 6_2006.mpg Hopefully it works outside of the UK as well

Yep that worked.... although the quality is so-so... looks ok on static scenes but anywhere with lots of movement (like the horse race at the end) it starts blocking and getting jerky, making it hard to actually judge the ride of the car...(it's about 80MB, for anyone not wanting to download too much...)

I grabbed the one from uknova though and its dvd quality

Thanks all..

Regards,
Simon

ACTIVE8 · Post by **ACTIVE8** » 07 Jun 2006, 12:28

Well thanks are due to those who provided the links, to enable us all to see the Citroen feature on Top Gear.

rossnunn · Post by **rossnunn** » 07 Jun 2006, 13:56

I have to admit I was a little dissapointed, I was hoping for more. More detail, more proper driving. I do hope TG isn't going how 5th gear has gone, loads of little mini test's that don't really tell you anything

406 V6 · Post by **406 V6** » 07 Jun 2006, 14:21

Chaps, one thing that intrigued me on the official C6 site: "for the firts time, variable damping". Doesn't an HA car have variable damping and springiness? I mean, on a regular HA2 car you control a central sphere with no damping. So you get the damping area of the 2 corner spheres and the 0 damping from the central one, plus the addition of the total volume of the 3 spheres...right?
What's escaping me then?

deian · Post by **deian** » 07 Jun 2006, 17:45

i think it's more technical than that... what i think they mean is like this...
there is a certain amount of pressure in the speheres that make them fall into pot holes, but also compress nicely up when going over bumps in relation to the cars weight...

But damping is (in spring cars) all about keeping the wheel on the road rather than letting it bounce on with the springs, and damping in hydropneumatic cars (as i understand) is controlled by the size and shape of the hole(s) in the strut spheres.

So I think there is a 'technical' difference (somewhere) between hard/soft ride (switching in the center sphere to give a softer ride) and damping.

I suggest it is all down to how harsh the ride will be, some people do prefer a harsh ride or they feel sea sick. But I myself don't think this is the reason, why they wanted to complicate the suspension by giving it variable damping is beyond me, the ability to switch between soft/hard ride and controlling the height (automatic lowering at high speeds in the hydractive 3+) is enough for me. Anyone else got any suggestions?

wheeler · Post by **wheeler** » 07 Jun 2006, 18:19

406 V6 wrote:Chaps, one thing that intrigued me on the official C6 site: "for the firts time, variable damping". Doesn't an HA car have variable damping and springiness? I mean, on a regular HA2 car you control a central sphere with no damping. So you get the damping area of the 2 corner spheres and the 0 damping from the central one, plus the addition of the total volume of the 3 spheres...right?
What's escaping me then?

On HA3+ you only have hard or soft,with the AMVAR system there are 16 levels of dampening (controled automaticaly hundreds of times a second) & each strut can have a totaly different level of dampening at the same time depending on road conditions.

406 V6 · Post by **406 V6** » 07 Jun 2006, 18:25

But keep up with me on this.
A year back or two, when i got the C5 and changed the spheres, we had this bit of talk in that the damping area and spring effect on a regular HA suspension is increased when the central sphere is at service (i proposed too add a central sphere and comute manually between settings) - let's say the central sphere has also dampers. So instead of an area of 3sqcm for 2 spheres we have a total area available for fluid to pass with the central sphere of 5sqcm.
Normal hydraulic shock absorbers work using the same basic principle of fluid passing through orifices/rings, the amount of resistance the fluid has to overcome through the orifices determines the damping factor. Common, why is a HA car off harder and more bouncy than when it's on?
If we now add the central sphere volume/pressure to the system, the springing medium is also increased. And if we consider pulse width modulation of the electrovalves, the whole system has a miriade of spring/damping rates, felt by us.

What they probably mean is independant damping for each wheel. Having 4 spheres per axle may mean 2 spheres er wheel, thus different settings per wheel too.

Edit: saw your post now Wheeler. but am i not correct of the PWM technic? i believe i read somewhere (Tramontana?) that there are damper incorporated along the tubing on a HA car system.

rossnunn · Post by **rossnunn** » 07 Jun 2006, 19:14

cricky! 2 per leg? imagine the cost when they start going wrong.

Mandrake · Post by **Mandrake** » 07 Jun 2006, 20:45

406 V6 wrote:Chaps, one thing that intrigued me on the official C6 site: "for the firts time, variable damping". Doesn't an HA car have variable damping and springiness? I mean, on a regular HA2 car you control a central sphere with no damping. So you get the damping area of the 2 corner spheres and the 0 damping from the central one, plus the addition of the total volume of the 3 spheres...right?
What's escaping me then?

Its not variable... theres only a hard and a soft mode with nothing in between. The soft mode is rather soft, and the hard mode is very firm.

Presumably the C6 has variable inbetween damping rates. Also the hard and soft mode applies to all wheels at once, and it sounds like the C6 can adjust it per wheel.

By the way there is not "0 damping from the central one" in Hydractive(2), there are two damping valves in each of the Hydractive regulator blocks which interrupt the flow between the centre sphere and either side.

These valves are very much like (ok, identical to) the the damping valves in normal spheres, except they're tuned with relatively soft opening thresholds, and have a 1.1mm bypass hole. This low threshold is what gives the HA its comfy soft ride compared to the standard Xantia's...

The strut spheres on a Hydractive(2) car have stiffer than normal opening thresholds and small bypass holes, (About 0.7mm and 0.6mm) which gives you your stiff "sporty" damping in the hard mode.

In Hydractive(2) these central damper valves also control the side-to-side oil flow during body roll, and if they werent there, then the large gauge pipe between the sides (10mm) would allow the car to "flop about like a boat" as Clarkson put it

(To say nothing of the vertical oscillations that would happen as well....)

Regards,
Simon

Mandrake · Post by **Mandrake** » 07 Jun 2006, 21:06

406 V6 wrote:But keep up with me on this.
A year back or two, when i got the C5 and changed the spheres, we had this bit of talk in that the damping area and spring effect on a regular HA suspension is increased when the central sphere is at service (i proposed too add a central sphere and comute manually between settings) - let's say the central sphere has also dampers.

Which in fact it already does

(see my previous post)

So instead of an area of 3sqcm for 2 spheres we have a total area available for fluid to pass with the central sphere of 5sqcm.
Normal hydraulic shock absorbers work using the same basic principle of fluid passing through orifices/rings, the amount of resistance the fluid has to overcome through the orifices determines the damping factor.

Yep, although its not quite as simple as that because most hydraulic dampers are deliberately non-linear devices. If you just have holes, you get a linear damping effect where the damping increases with the oil flow velocity - hence not enough damping for very small/slow movements causing the car to "float".

Make the holes smaller to give more damping for small movements and now you restrict the oil flow for large movements. (eg big bumps) On these big bumps the suspension simply couldn't travel over the bump and you'd hit it very hard. (and maybe damage the suspension) Not good.

To solve this the valves have threshold plates which give "2 stage damping", which is the standard used in most cars, including standard Hydropneumatic.

Basically you have two paths for the oil to flow through - a small "bypass" hole which is always open, and some much larger holes which are blocked by some spring steel washers. For small movements (read oil velocity) there isn't enough pressure differential built up to bend the washers, so the oil flows only through the bypass hole.

For a large sudden bump you get a large instantaneous pressure differential which can't be equalized by the small bypass hole, so the washers bend and open the large holes to allow the oil to flow. The bending of the washers is progressive too.

Generally the best ride is achieved when the natural rebound force is not QUITE strong enough to open the washer valves, but bumps can open the valves. This gives a very steady ride, and is approximately how many Citroen's are tuned.

This can only be achieved with a fairly soft springing rate, with stiffer springing a threshold valve can't differentiate between the force of a bump and the rebound force, since stiffer springing gives a stronger rebound. Most conventionally sprung cars can't be sprung softly enough for this to work.

In Hydractive(2) you now how two paths for the oil to flow - to the centre sphere through a damper valve with a large bypass hole (1.1mm) and soft washer plates, and into the strut spheres which have a smaller hole (0.7mm) and stiffer washer plates.

This means in Hydractive(2) soft mode, you effectively have *3 stage damping* which gives more progressive control. Very small movements (undulations) flow only through the bypass holes, and primarily into the middle sphere due to the area differential.

Moderate bumps open the washer valves in the central block but not the ones in the strut spheres, while very abrupt bumps open both the central and strut washer valves.

The neat thing about this is that it makes the rebound more progressive too - a soft bump which causes oil flow mainly into the centre sphere also has a soft rebound because it returns back through the same valve, while a large sudden bump forces a significant percentage of the oil into the strut spheres which means the rebound for the oil coming back out of those spheres is strongly damped too.

So - soft bump, gentle rebound control = comfortable ride, while a violent bump automatically gets its rebound more heavily damped = better body control. This all happens without the computer even switching modes.

In the hard mode the centre sphere is blocked off, as is the flow of oil from left to right, and you're left with stiff 2 stage damping, which gives the characteristic hard mode feel.

Common, why is a HA car off harder and more bouncy than when it's on?
If we now add the central sphere volume/pressure to the system, the springing medium is also increased.

Yes, but remember that in switching between soft and hard mode both the springing rate AND the damping rate are changed.

And if we consider pulse width modulation of the electrovalves, the whole system has a miriade of spring/damping rates, felt by us.

No, there is no pulse width modulation of the springing/damping going on. The valve is only ever hydraulically open or closed. There is a pulse waveform driving the valve but that is ONLY to reduce power dissipation, its not used to provide variable damping rate in any way.

What they probably mean is independant damping for each wheel. Having 4 spheres per axle may mean 2 spheres er wheel, thus different settings per wheel too.

Edit: saw your post now Wheeler. but am i not correct of the PWM technic? i believe i read somewhere (Tramontana?) that there are damper incorporated along the tubing on a HA car system.

In the hydractive control block

Regards,
Simon

406 V6 · Post by **406 V6** » 07 Jun 2006, 22:05

Ah, great posting Mandrake, hats off!

I really thought that PWM was used also to variate the valve opening times, like you do with an electric motor, for instance, on a Segway.

BTW, i saw the C6 video from Jeremy. I just looove it when he says "This is un-be-LI-veably smooth" and "it's like driving over silk!"

:D

Clogzz · Post by **Clogzz** » 08 Jun 2006, 12:58

406 V6 wrote:Ah, great posting Mandrake, hats off!

Sensational expertise, isn’t it ?
I often wonder if Simon is working in a secret studio, doing work for Citroën, and collecting ‘reparation’ payments for France’s past crime against New Zealand.