Does anyone know where I can find the correct sphere pressure for my Xantia hydractive? I have bought some form AS which state a 55bar but it seems I have 65bar ones fitted (at least, there is 65 stamped on them - I assume thats the pressure). If they are 65 and should be 55, what effect would that have on the ride...harder or softer?
FYDAMF
Correct Sphere Pressure
Moderator: RichardW
A week ago I examined GS spheres, and found number 65 stamped somewhere at the waist, don't know it's meaning, and 55 near the screw, which is the pressure of GS front spheres.
HA2 spheres for Xantia are:
- front, side: 450 cm3 / 45 bar or 400 cm3 / 50 bar
- rear, side: 400 cm3 / 30 bar (berline) or 40 bar (break)
- front, middle: 450 cm3 / 75 bar or 500 cm3 / 70 bar
- rear, middle: 400 cm3 / 50 bar
You can get more info in the download section of this forum. Xantia spheres have identification number stamped on them, so you can check.
The ride is softer if the product volume x pressure is higher, but it also depends on the damper valves on the sphere.
You can get some extra info in this topic:
http://www.andyspares.com/discussionfor ... IC_ID=2002
Alex
HA2 spheres for Xantia are:
- front, side: 450 cm3 / 45 bar or 400 cm3 / 50 bar
- rear, side: 400 cm3 / 30 bar (berline) or 40 bar (break)
- front, middle: 450 cm3 / 75 bar or 500 cm3 / 70 bar
- rear, middle: 400 cm3 / 50 bar
You can get more info in the download section of this forum. Xantia spheres have identification number stamped on them, so you can check.
The ride is softer if the product volume x pressure is higher, but it also depends on the damper valves on the sphere.
You can get some extra info in this topic:
http://www.andyspares.com/discussionfor ... IC_ID=2002
Alex
Alex,
I used your equation to check my sphers (which is very useful when you don't know the history of the spheres -like mine..
The rears, as I suspected, are low , around 18 using you formula
However, the same test on the front reveals something strange..
The resultant pressure using your formula is 55bar when I should have either 50 or 45 depending on the sphere fitted(the i.d. is hidden so I'll have to undo the sphere a little to find out)
Your/anyones comments on this would be appreciated
p.s. Can't get one of the rears undone..any hints (not got a AS removal tool...yet)
FYDAMF
I used your equation to check my sphers (which is very useful when you don't know the history of the spheres -like mine..
The rears, as I suspected, are low , around 18 using you formula
However, the same test on the front reveals something strange..
The resultant pressure using your formula is 55bar when I should have either 50 or 45 depending on the sphere fitted(the i.d. is hidden so I'll have to undo the sphere a little to find out)
Your/anyones comments on this would be appreciated
p.s. Can't get one of the rears undone..any hints (not got a AS removal tool...yet)
FYDAMF
Hi, Hippy!
I'm glad to see there's someone interested in this discussion.
Well, this subject is really tough for me, so I'm about to throw my university grade through the window.
I checked one BX's front sphere at the other garage, and they measured slightly lower pressure, "50 bar", which is a little suspicious, as it was filled to "58 bar" 2 months ago. But, it's still much higher than I calculated. They also told me that spheres are still OK.
So I did some more research. In my calculation, I first made prediction that volume of nitrogen inside sphere is 95% of it's internal volume, as some space is used by the rubber diaphragm. I checked the program on C5 data from J. Marsh site and got very similar results. Than, I gradually lowered that predicted value to 68%, which seemed more realistic. After I returned from that garage, I concluded that 68% was still too optimistic, because the results from program were far lower than measurments in two different places. Then, I opened the screw on that old GS sphere found in father's garage, poured water in it, and measured it's 'effective' volume. It turned out that declared volume IS volume of nitrogen, as exactly 400 ml of water came out from sphere.
I modyfied my program again and the results on C5 2.2 Hdi (from J.Marsh) now matched with less than 1% error (!) on both hard and soft mode, unladen and laden car.
According to that, the formula should be:
p = dh * m * (m + mt) / (2.38 * V * mt)
... so your spheres may have about 12 bar rear, 37 bar front. Are you sure you did the measurment in hard mode?
On the other side, I simply can't believe that pressure-meter can give such an error, although I was told by the friend who works in chemistry that pressure meters of such size (about 10 cm diameter) usually have even 10% error on the full scale (15 bar in this case - it has 150 bar scale). He told me that mechanical pressure-meters with 1% error are reeeeeeally biiiig.
I would appreciate anyone's comment here. It's impossible for me to find a car with new spheres and check the formula in reality, because used cars have very old spheres.
Otherwise, I'll have to give up and buy Volkswagen next time. Or even Yugo ...
And the hint about removing a sphere - hit it tangetionally somewhere at the waist with a chisel and hammer. It usually works.
I'm glad to see there's someone interested in this discussion.
Well, this subject is really tough for me, so I'm about to throw my university grade through the window.
I checked one BX's front sphere at the other garage, and they measured slightly lower pressure, "50 bar", which is a little suspicious, as it was filled to "58 bar" 2 months ago. But, it's still much higher than I calculated. They also told me that spheres are still OK.
So I did some more research. In my calculation, I first made prediction that volume of nitrogen inside sphere is 95% of it's internal volume, as some space is used by the rubber diaphragm. I checked the program on C5 data from J. Marsh site and got very similar results. Than, I gradually lowered that predicted value to 68%, which seemed more realistic. After I returned from that garage, I concluded that 68% was still too optimistic, because the results from program were far lower than measurments in two different places. Then, I opened the screw on that old GS sphere found in father's garage, poured water in it, and measured it's 'effective' volume. It turned out that declared volume IS volume of nitrogen, as exactly 400 ml of water came out from sphere.
I modyfied my program again and the results on C5 2.2 Hdi (from J.Marsh) now matched with less than 1% error (!) on both hard and soft mode, unladen and laden car.
According to that, the formula should be:
p = dh * m * (m + mt) / (2.38 * V * mt)
... so your spheres may have about 12 bar rear, 37 bar front. Are you sure you did the measurment in hard mode?
On the other side, I simply can't believe that pressure-meter can give such an error, although I was told by the friend who works in chemistry that pressure meters of such size (about 10 cm diameter) usually have even 10% error on the full scale (15 bar in this case - it has 150 bar scale). He told me that mechanical pressure-meters with 1% error are reeeeeeally biiiig.
I would appreciate anyone's comment here. It's impossible for me to find a car with new spheres and check the formula in reality, because used cars have very old spheres.
Otherwise, I'll have to give up and buy Volkswagen next time. Or even Yugo ...
And the hint about removing a sphere - hit it tangetionally somewhere at the waist with a chisel and hammer. It usually works.
Alex hi!
I didn't check it hard mode..whats the reason for this? Also, should it be on normal ride height as the suspension gets stiffer in higher mode. Also, I measure at the wheel arch, vertically above the axle line and not the bumper...that ok?I'm hopefully going to change the rears tomorrow and I will post the old and new results taken from your revised formula
Another note, we 'spoke' about the bigger the pressure*volume gives a softer ride but the bore must also be considered. Am I correct in assuming that the bigger the bore, again the softer the ride and so in order to select the softest ride from the variation of suitable spheres, the highest product of pressure*volume*bore should be used...is this the case you think?
thanks for your help
FYDAMF
I didn't check it hard mode..whats the reason for this? Also, should it be on normal ride height as the suspension gets stiffer in higher mode. Also, I measure at the wheel arch, vertically above the axle line and not the bumper...that ok?I'm hopefully going to change the rears tomorrow and I will post the old and new results taken from your revised formula
Another note, we 'spoke' about the bigger the pressure*volume gives a softer ride but the bore must also be considered. Am I correct in assuming that the bigger the bore, again the softer the ride and so in order to select the softest ride from the variation of suitable spheres, the highest product of pressure*volume*bore should be used...is this the case you think?
thanks for your help
FYDAMF
Hippy,
both pressure x volume and damper valve(s!) affect the ride, but on different way.
Nitrogen in spheres acts like the spring. Higher the product p x V, lower the "spring rate" and the car's "eigen frequency". Citroen vehicles have with new spheres eigen frequency somewhere around 0.8-1 Hz, depending on load (higher the load, higher the frequency). Vehicles with conventional suspension have higher eigen frequency (usually around 1.5 Hz), especially on the rear axle, because when the car is fully laden, most of it's load is supported by rear axle, and most cars have no self-leveling. On such vehicles, eigen frequency is lower with higher load, so ride is more comfortable in bigger (and heavier) cars. If the spring rate is high, ride is 'bouncy' on longer road irregularities.
Damper valves damps oscilatory movements of the car and of the wheels also. If the valves are small, the ride is more "damped", but also more "harsh" on shorter and sharper road irregularities. Construction is essentially the same in both conventional and hydropneumatic suspension. In the case of Citroen, damper valves are on the spheres. There's one small central bore (in fact - not very important), and also 8 bigger holes, which open under pressure.
If you are checking the spheres with my equation, you must do just as I wrote. The "dive" on the wheel arch will be lower than on the bumper, so the results won't be correct. Also, the car must be in the hard mode, when middle spheres are not in play, as I said. But, I don't know if it's possible to measure the dive in the hard mode, because of very small central bores in HA spheres, so the car will dive slowly. If the car has anti-sink, rear mesurment must be taken some time after switching off the engine, when rear anti-sink valve is closed.
I think it's also possible to check the middle HA sphere this way, using the difference in dive in hard and soft mode as dh, and half of the middle sphere's volume as V.
Complicated, isn't it? It's more simple to check the spheres in some garage, hoping their pressur-meter is OK.
Alex
both pressure x volume and damper valve(s!) affect the ride, but on different way.
Nitrogen in spheres acts like the spring. Higher the product p x V, lower the "spring rate" and the car's "eigen frequency". Citroen vehicles have with new spheres eigen frequency somewhere around 0.8-1 Hz, depending on load (higher the load, higher the frequency). Vehicles with conventional suspension have higher eigen frequency (usually around 1.5 Hz), especially on the rear axle, because when the car is fully laden, most of it's load is supported by rear axle, and most cars have no self-leveling. On such vehicles, eigen frequency is lower with higher load, so ride is more comfortable in bigger (and heavier) cars. If the spring rate is high, ride is 'bouncy' on longer road irregularities.
Damper valves damps oscilatory movements of the car and of the wheels also. If the valves are small, the ride is more "damped", but also more "harsh" on shorter and sharper road irregularities. Construction is essentially the same in both conventional and hydropneumatic suspension. In the case of Citroen, damper valves are on the spheres. There's one small central bore (in fact - not very important), and also 8 bigger holes, which open under pressure.
If you are checking the spheres with my equation, you must do just as I wrote. The "dive" on the wheel arch will be lower than on the bumper, so the results won't be correct. Also, the car must be in the hard mode, when middle spheres are not in play, as I said. But, I don't know if it's possible to measure the dive in the hard mode, because of very small central bores in HA spheres, so the car will dive slowly. If the car has anti-sink, rear mesurment must be taken some time after switching off the engine, when rear anti-sink valve is closed.
I think it's also possible to check the middle HA sphere this way, using the difference in dive in hard and soft mode as dh, and half of the middle sphere's volume as V.
Complicated, isn't it? It's more simple to check the spheres in some garage, hoping their pressur-meter is OK.
Alex
Hi Alex,
is the calculated dive not effected by the distance from the bumper to the axle and would therefore vary depending on which model(xm/bx/xantia/gs etc)?
Also, when you mention test in hard mode, do you mean (1) engine running with 'sport' setting on (HAII) or (2) you mean with engine off in normal setting after 30secs or so(of engine stopping)
I need to quantify this as If the results show the spheres are ok, I'll return the unused new ones and get my money back.
When on motorway, the ride is ok (I prefer my bx tho') but on slower country roads it feels harsh and this is why I am not sure wether to replace them or not.
Thanks for your help and prompt replies on this..
FYDAMF
is the calculated dive not effected by the distance from the bumper to the axle and would therefore vary depending on which model(xm/bx/xantia/gs etc)?
Also, when you mention test in hard mode, do you mean (1) engine running with 'sport' setting on (HAII) or (2) you mean with engine off in normal setting after 30secs or so(of engine stopping)
I need to quantify this as If the results show the spheres are ok, I'll return the unused new ones and get my money back.
When on motorway, the ride is ok (I prefer my bx tho') but on slower country roads it feels harsh and this is why I am not sure wether to replace them or not.
Thanks for your help and prompt replies on this..
FYDAMF
Hippy,
don't rely on my equation too much anyway. It's true that, it seems, currect results on C5 can hardly be coincidence, but on the other side, I still can't believe that two pressure-meters (altough, it seems, from the same manufacturer) can show twice the real pressure, as in the case of my BX. It would be fine if someone with new spheres can confirm if I am at least near the reality with that.
As you notice, correct result depends on the ratio:
distance from measuring point to one axis
-------------------------------------------
distance from measuring point to other axis
In my program / equation, this ratio is presumed to be 1:5.5 . Depending on the model, it's somewhat different, but not much, so there could be some 5% error because of that.
In the case of HA2, suspension can be in soft or hard mode in both 'sport' and 'comfort' setting, depending of the computer decision. So, you must switch off the engine and close the door. After about 30s the system will switch the suspension to hard mode (disconnect the middle spheres).
I am also not satisfyed with harsh ride in my BX on country roads. On your Xantia, the reason can also be in HA2 system not working properly, sticking to hard mode most of the time. Try using this trick from Tramontana site:
"As H II systems use a 1 kHz chopper to form the current operating the valves, this leads to an interesting way to learn the current status of the suspension: this chopped current actually disturbs the radio reception. Tune your radio to a spot somewhere near 700 kHz where there is no incoming broadcast. When the solenoid valves are energized (that is, the suspension is in soft mode), you will hear a characteristic buzzing sound from the radio. As you drive around, you can observe what triggers the hard mode erroneously."
Alex
don't rely on my equation too much anyway. It's true that, it seems, currect results on C5 can hardly be coincidence, but on the other side, I still can't believe that two pressure-meters (altough, it seems, from the same manufacturer) can show twice the real pressure, as in the case of my BX. It would be fine if someone with new spheres can confirm if I am at least near the reality with that.
As you notice, correct result depends on the ratio:
distance from measuring point to one axis
-------------------------------------------
distance from measuring point to other axis
In my program / equation, this ratio is presumed to be 1:5.5 . Depending on the model, it's somewhat different, but not much, so there could be some 5% error because of that.
In the case of HA2, suspension can be in soft or hard mode in both 'sport' and 'comfort' setting, depending of the computer decision. So, you must switch off the engine and close the door. After about 30s the system will switch the suspension to hard mode (disconnect the middle spheres).
I am also not satisfyed with harsh ride in my BX on country roads. On your Xantia, the reason can also be in HA2 system not working properly, sticking to hard mode most of the time. Try using this trick from Tramontana site:
"As H II systems use a 1 kHz chopper to form the current operating the valves, this leads to an interesting way to learn the current status of the suspension: this chopped current actually disturbs the radio reception. Tune your radio to a spot somewhere near 700 kHz where there is no incoming broadcast. When the solenoid valves are energized (that is, the suspension is in soft mode), you will hear a characteristic buzzing sound from the radio. As you drive around, you can observe what triggers the hard mode erroneously."
Alex
I tried the radio 700khz test yesterday and today but cant find a spot that picks up any difference between sport and comfort..
Is there a way of using a meter to test for signal to solenoid that switches between sport and comfort?
Anyway, thanks alot for your input, If you need results from my bx (I know the history of the spheres) I am happy to send them to you but the spheres are not new..they have been recharged once and have covered 27K since...my local garage rekons if you recharge around every 50K miles then you should prevent any perforation of the diaghram
FYDAMF
Is there a way of using a meter to test for signal to solenoid that switches between sport and comfort?
Anyway, thanks alot for your input, If you need results from my bx (I know the history of the spheres) I am happy to send them to you but the spheres are not new..they have been recharged once and have covered 27K since...my local garage rekons if you recharge around every 50K miles then you should prevent any perforation of the diaghram
FYDAMF
I think the suspension mode changes can be observed using a volt-meter, with one wire connected to one of valves (or ECU output to valves), and other wire grounded, if the "radio trick" doesn't work. Valve's nominal voltage is 2.6 V. Alternate current is used to minimise heat buildup.
Where is the hydractive ECU in Xantia anyway? Can't find any info in Haynes manual.
Of course, if you drive aggressivly on a winding country road, the suspension will probably spend most of the time in hard mode even in "comfort" setting, because it will be constantly triggered by body movement, steering wheel, accelerator and brake sensor.
If it turns out that everything is OK (spheres and HA system) and you are still not satisfyed with the ride, you have the last option - you can fit non-hydractive spheres and disconnect the ECU - you will get non-hydractive Xantia. Or even leave ECU connected, as some C5 owners does.
Please, write the "measurments" for your BX anyway, so I can compare them with mine. So far I found two BX-es which were softer than mine on the rear, although the spheres were not new (don't know how old). Under my weight (70 kg) rear end dived about 8 cm on first, and 7 cm on second one, while on mine 6.5 cm was maximum with renewed spheres, and now, after 10 months, it's about 5.7 cm.
Huh, is this all really worth the effort? I'm really considering buying an 'ordinary' car and spending my time to something more usefull ...
Where is the hydractive ECU in Xantia anyway? Can't find any info in Haynes manual.
Of course, if you drive aggressivly on a winding country road, the suspension will probably spend most of the time in hard mode even in "comfort" setting, because it will be constantly triggered by body movement, steering wheel, accelerator and brake sensor.
If it turns out that everything is OK (spheres and HA system) and you are still not satisfyed with the ride, you have the last option - you can fit non-hydractive spheres and disconnect the ECU - you will get non-hydractive Xantia. Or even leave ECU connected, as some C5 owners does.
Please, write the "measurments" for your BX anyway, so I can compare them with mine. So far I found two BX-es which were softer than mine on the rear, although the spheres were not new (don't know how old). Under my weight (70 kg) rear end dived about 8 cm on first, and 7 cm on second one, while on mine 6.5 cm was maximum with renewed spheres, and now, after 10 months, it's about 5.7 cm.
Huh, is this all really worth the effort? I'm really considering buying an 'ordinary' car and spending my time to something more usefull ...
Alex - it's nice to see someone trying a mathematical approach to this problem - otherwise it's nearly all down to "feel". Your input is appreciated.
There is at least one other extraneous factor, but forgive me if you have already discounted this. If the rear arm bearings are at all worn, or starting to corrode due to water ingress, then the travel of the rear suspension can be restricted, which might cause problems with your test.
My totally unscientific test is to see whether the rear of the car can be lifted easily by grabbing under the bumper and bouncing the rear upwards and downwards. There should not be any obstruction or stiffness to the travel of the rear suspension if the rear arm bearings are in good condition. Any stiffness in travel should become apparent with this "test".
There is at least one other extraneous factor, but forgive me if you have already discounted this. If the rear arm bearings are at all worn, or starting to corrode due to water ingress, then the travel of the rear suspension can be restricted, which might cause problems with your test.
My totally unscientific test is to see whether the rear of the car can be lifted easily by grabbing under the bumper and bouncing the rear upwards and downwards. There should not be any obstruction or stiffness to the travel of the rear suspension if the rear arm bearings are in good condition. Any stiffness in travel should become apparent with this "test".
I know how you feel, I've almost lost intrest in the bloomin spheres on the xantia myself BUT I like the car (love my BX much much more) and I guess thats why we do it..I for one would not be satisfied with an 'ordinary' car (with the exception of Alpha Romeo - cos at least, like cits, they have character) Nearly sold the xantia in favour of a classic and use the trusty bx for all the workhorse stuff (i.e. lugging the family round) but the xantia is quieter and above safer so it stayed..it was shown the exit door but crawled back under my skin and made itself comfortable next to my wallet!! So, it stays, and there we have it, we moan like crazy but we love them, we enthuse and would be lost without them..we wouldn't know what to do with our spare time..
Anyway, will post bx measurements for you but may take a few days..maybe this weekend
ciao for now
FYDAMF
Anyway, will post bx measurements for you but may take a few days..maybe this weekend
ciao for now
FYDAMF
DLM,
I have sorted the rear arm bearings about a year ago. The ride improved, but it's stil harsh on the sharper bumps. Unfortunately, there's the same construction and problems on Xantias.
The problem may also be in front cylinders, althoug one was also replaced 5 years ago. Fortunately, construction on Xantia is different here.
Hippy,
Talking about Alfa, my father bought one (Alfa 156 1.6) 4 years ago and retained GSA as a second car. Nice car, but really firmly sprunged, although I must admit, the ride over the potholes and similar things is smoother than in my BX. But, it's really a car for two. Rear suspension is, in fact, softer than in other cars (dive = 3 cm under my weight), so the car is overloaded with 4 adults on board, and you can frequently feel rear bump stops on undulated roads. So, Nivomats on the rear are worth considering if buying 156. Otherwise, the car really rails, it's very quiet, and the A/C is superb, better designed than in most other cars. Only, 1.6 engine is to weak for it.
Don't hurry with bx measurments, I'm planning to sell it anyway and buy, huh, maybe Xantia, maybe something else.
I have sorted the rear arm bearings about a year ago. The ride improved, but it's stil harsh on the sharper bumps. Unfortunately, there's the same construction and problems on Xantias.
The problem may also be in front cylinders, althoug one was also replaced 5 years ago. Fortunately, construction on Xantia is different here.
Hippy,
Talking about Alfa, my father bought one (Alfa 156 1.6) 4 years ago and retained GSA as a second car. Nice car, but really firmly sprunged, although I must admit, the ride over the potholes and similar things is smoother than in my BX. But, it's really a car for two. Rear suspension is, in fact, softer than in other cars (dive = 3 cm under my weight), so the car is overloaded with 4 adults on board, and you can frequently feel rear bump stops on undulated roads. So, Nivomats on the rear are worth considering if buying 156. Otherwise, the car really rails, it's very quiet, and the A/C is superb, better designed than in most other cars. Only, 1.6 engine is to weak for it.
Don't hurry with bx measurments, I'm planning to sell it anyway and buy, huh, maybe Xantia, maybe something else.