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Citroen C6 Suspension Analyser Android / iPhone app |
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jekkeri
 
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  Member No: #1905
Location: Tallinn |
Dear fellow forum members, Having witnessed (and experienced) many times the haunting feeling of not knowing if C6 suspension is working correctly or not, I have a suggestion I'd like to get some comments to. We all know what usually happens when you feel that your C6 is not wafting like it used to - you go to the dedicated Citroen service and they tell you "that's how they all are sir". After all, it would be unrealistic to expect every Citroen mechanic - or even every Citroen service shop - would know exactly how a C6 should feel when suspension is working perfectly. Common problems and doubts regarding C6 suspension are, among others: - pitching: C6 rocks back-forth so much that sometimes the rear bottoms out in "wavy road" conditions. The car feels on some roads like a see-saw - rocking: C6 tilts from side-to-side in roads that have one-sided bumps or is heavily tilted towards gravel - hardness: C6 suspension feels stiffer "than it should" but Citroen mechanics still say "that's how they all are Sir" - AMVAR / Extra spheres: there are many error modes that do not cause any fault codes, just "strange" behaviour of suspension in some specific kind of roads and speeds. One example is read center hydraulic block that may cause one side of rear suspension to be stiffer on real road conditions, even if all Diagbox/Lexia tests show that both AMVAR and extra spheres solenoid are working. Only in the most obvious cases of these problems Diagbox/Lexia fault codes help. Usually the case is, no evident fault codes exist but still the suspension feels "off" or "wrong". After this low prelude, I move to my proposition: I could design a mobile application that uses accelerometers and gyros (found in almost every modern smart phone) to analyze suspension of Citroen C6 on a certain kind of test track, and report what seems to be wrong. Excessive pitching 0-10, Excessive tilting 0-10, Excessive rocking 0-10, Suspension spring constants LF/RF/LR/RR 0-10, Suspesion AMVAR effect LF/RF/LR/RR, suppleness on small bumbs 0-10 LF/RF/LR/RR. The challenge here - where I need help - is the test track configuration. It is obvious that the biggest issue here is the need to create a simple enough test track that (almost) every C6 enthusiast can easily make it with cheap "rubber road bumbs" etc. It should contain left/right separate bumbs of known height and profile, most likely around 12-14 cm, then smaller "sharp" bumps, and at least two consecutive "wavelike" bumps to analyse the pitching. The final app would be sold in Apple app store and Google play. I feel this kind of app would serve as invaluable tool of evaluating C6 suspension problems. Without it, it's difficult - writing to forums how the problems "feels", and every single person feels little bit differently of course, there is no common scale of measuring process to these suspension problems at the moment. So; do you, fellow members of this forum, feel that this kind of app would have a purpose in this world? |
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gmerry
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   Member No: #21
Location: Scotland |
Jekkeri, very interesting proposal. I think Citroen really missed a trick in terms of not building in some of this into either the on-board diagnositics (all the accelerometers are already installed) and/or Lexia. There is a simple Lexia routine to check that the AMVAR actuators are working: (relies on manually rocking the car with AMVAR actuators in their various conditions). They could have added an additional routine to check the centre sphere actuators. One could approach this as comparative response (against a standard good car) assessment but this would require some degree of accuracy in the forcing function (variables are driving speed, driver inputs, the "bump" geometry. This seems to be your approach. Other variables include rubber components such as tyres and suspension bushes, the suspension fluid temperature (depends on ambient and degree of work the fluid has done) and I think very importantly, the amount of dissolved gas in the system - anyone ever had that super floatiness after suspension height changes? Another big variable is the computer algorithms! This might be factored out by a Lexia routine that set the suspension to standard fixed damping factors etc Another approach is to better monitor the actual working components: suspension sphere pressures (sphere micro strain gauges) etc. Nice to know someone is thinking about this stuff. Best regards G |
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C6Dave
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  Member No: #1
Location: Northumberland |
As G says interesting but.... How would you create a 'reference' ride quality point to compare all other cars with, given that there are no 'new' factory fresh c6's available? Plus there are differences between the V6 and non V6 engined cars in suspension set ups |
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jekkeri
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Member No: #1905
Location: Tallinn |
gmerry: It would be impractical to build in, if there was no "standardized test track", and it would be highly impractical to Citroen shops doing service. Plus, it is not in Citroen's main interest to keep the suspension working for 2nd and 3rd owners, as we know nowadays unfortunately. So in-board diagnostics for this in unrealistic to expect. On the latter part of your comment I can state that usually the problems in suspension would show in the accelerometer data in such degree that any effect of dissolved gas or worn bushes etc would be nearly irrelevant to my experience. Lexia/Diagbox tests are not really useful in many real situations where sensor input problems are the key. It does not help you to know that stiff/loose or AMVAR 0-16 scale works if sensors provide wrong information to BSI/CSS and therefore AMVAR or centre ball remain in stiff mode. For example, if height setting is incorrect or some height potentiometer readings are wrong because of wore out shaft, all Lexia tesst show correct results - but car wheels stiff or pitching back-forth all the time. Bad! C6Dave: Reference ride quality would not have to be build-in the app, it would be uploaded to internet when any car was tested. And, for the "first reference", there are 2012 cars with known good ride quality that some of us "the experts" can confirm, so this problem is not impossible to overcome. Regarding non-V6 cars, yes, they don't have AMVAR and are different. So what? Most of the enthusiast cars are V6 exclusive that all have AVMAR. We don't have to help the whole world, just provide some help to people close to us. This is by no means a perfect solution. But still I think it would be greatly superior to the current system - everyone trying to "write to forum" how they feel the suspension is not behaving correctly, based on the gut feeling. No diagnostic data, not comparative measurements can be done by a layman at the moment. I think you might agree this is not a preferable situation? |
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gmerry
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Member No: #21
Location: Scotland |
Hi all, some more thoughts:- The accelerometer inside the phone would give rubbish readings. An external fixed accelerometer, say mounted on the body/chassis near the top shock absorber would give a signal not compromised by the compliance between the source of the vibration and the instruments in the phone. Perhaps a better way of monitoring the suspension would be to fix the AMVAR damping at a fixed rate. Then lockout the stiffness regulator, drive the car and collect the suspension frequency response. Repeat with the suspension regulator locked in, drive the car and collect frequency response for the new condition. Regards G Note, the phone may still be of use as the data collection instrument but a PC would be better and a Fast Fourier Analysis programme would probably be used. Note this is all standard industrial stuff, would need some programming to control the suspension damping and stiffness regulators to the fixed settings. Note also, I pretty confident in the ability of my Mk I backside after driving a C6 for 6 years and sorting sphere and suspension bush problems. I'm sure there are good mechanics out there, who specialise in C6 maintenance, who would be able to offer similar accurate diagnosis |
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speedfix
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 Member No: #1043
Location: south west |
Maybe when time pemits I wiil get the old Hartridge shock tester up and running and do some tests on my cars in their different modes. The s/tester shown is all I could find and it is incomplete. I still have a box of paper feeds to show and compare results - Click Here - |
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speedfix
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Member No: #1043
Location: south west |
Just had a look for the test cards 200 in all don't know if one can still get them.  The tester looks complete, have not used it for years, stuck under a 500k in the back of a large building. Time to extract it and give it a going over with the c6s me thinks. Should point out any weak spheres and balance with testing of the working stiffness regulators and spheres. |
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Tjensen
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 Member No: #954
Location: Bergen |
Important to have a C6 Reference and not looking to other cars. You will measure "AMVAR + Hydractive at rest" ? Not so long ago my charging system was tested as faulty by a Citroen dealer. Saved 1200£ by checking further (this site very valuable)and the "problem" was that the C6 is more intelligent than other cars: no charging when its not needed and using braking/downhill energy for charging (3,0 Hdi. and some Rovers and other Citroens ?). |
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speedfix
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Member No: #1043
Location: south west |
IMO Amvar[road hook sky hook] will not be active with the static testing. This will be a shock sphere test in the different modes and balance between n/s and o/s [pointing to a failing sphere or both,] f/r testing. Seem to think some BMW minis have a clever charging system! |
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C6Dave
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Member No: #1
Location: Northumberland |
Tjensen wrote ... Not so long ago my charging system was tested as faulty by a Citroen dealer. Saved 1200£ by checking further (this site very valuable)and the "problem" was that the C6 is more intelligent than other cars: no charging when its not needed and using braking/downhill energy for charging (3,0 Hdi. and some Rovers and other Citroens ?).  You'll probably find more cars with the system to meet Euro 6 emission limits. No charge = less engine load so less fuel required = less emissions
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jekkeri
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Member No: #1905
Location: Tallinn |
Thank you for all the comments. Please forgive me for being so persistent in disagreeing on some of your points - I have professional experience in building accelerometer/gyro/magnetometer sensor solutions and sw for over 15 years, so I think I know what I am talking about. gmerry:"The accelerometer inside the phone would give rubbish readings..." Incorrect. With right fixation position - I am thinking center console upper box with flat rubber "floor" - the sensor data gathered from phone would reflect well the vibrations and motions the car body does. All the better that it would be centrally mounted, so left/right results can be directly compared. gmerry:"Perhaps a better way of monitoring the suspension would be to fix the AMVAR damping at a fixed rate..." Unfortunately, this is mainly dreaming. There is no fixing anything outside what Lexia and Diagbox do, and as you all have tested for sure, they are not so helpful in many cases. Protocols are not open so building "own" version of Diagbox to control C6 suspension just the way needed for testing would request too much work - manmonths or more. To my experience, only reliable tests with Diagbox are the suspension hard/soft valve STATIONARY function (does not tell how it works on the road!), and AMVAR valves stationary function (does not really separate inbound/outbound and different "stuck" modes). Somebody suggested stationary shock absorber testing. It can maybe tell if some sphere has flat-out collapsed or other similar "clear" errors that can be detected otherwise quite easily too, but it would not reveal the dynamic problems that occur when driving. I wrote about those problems in my first post. Most "subtle but annoying" C6 suspension problems manifest in speeds of 30-90 km/k, with certain road conditions. Rear bottoming out in wave-like bumbs and wafting too much, tilting from side-to-side, etc etc. These are currently impossible to diagnose outside "backside feeling", and like stated, many Citroen shops just blantly state "that's how they all are sir.". And yes, I know there are some guys who can tell right out of the bat what is wrong with certain C6 ride quality. Having driven these ultimate Citroen primadonnas for years I too have quite extensive "feel" at least to tell if something is wrong or not. However I dare say not many of them can state with high accuracy what causes the problems, since symptoms for many problems are similar. Wrong height settings (2 mm can cause dramatic difference), worn out height potentiometer links, sticking AMVAR, sticking rear center hydraulic block, the list is long! Finally, about the app itself. The processing power and screen quality of modern smart phones is such that there is no need at all to have that app in PC. It would run smoothly on mobiles - and results and analysis would be instant of course. This kind of tool would naturally give interesting opportunity to compare ride quality and bumb absorbtion capabilities of "normal" cars to C6, but this is secondary concern here, of course. However, if you all feel there is no need for such an app, I will probably not do it. |
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speedfix
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Member No: #1043
Location: south west |
"Unfortunately, this is mainly dreaming. There is no fixing anything outside what Lexia and Diagbox do" jekkeri , sorry I'm in total disagreement on that statement. Many suspension problems can diagnosed and repairs carried out without the use of lexia etc. You have stated problems with your c6 that are staring at you to fix. Go put your car on a track day at speeds in excess of 100mph to confirm the active suspension is working. Your other faults described can be delt with without to much of a problem. I to had a bump/rebound prob on my C6 2.2. after purchase but was told from Citroen nothing wrong, finally got round to checking the ride hieghts f/r, re adjusted the front link to a lower position, just under a mm and made all the difference. As for your side to side motion I would first check your shock spheres on a shock machine. The centre hydraulic block sticking you will know when that happens ie solid fixed position etc. Out of intrest what sort of mileage has the car done and have you changed the LDS fluid at all. I wish you all the luck with your app idea if you do proceed with it , it will of course be above my head on the workings! When all is well with the car IMO the car is a total winner. |
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Tjensen
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Member No: #954
Location: Bergen |
The app would be a very welcome addition. Especially after 1989 (XM) and Hydractive it became quite difficult to link strange behavior to actual problems that can be fixed. With Hydractive III+ and AMVAR it would be very nice. And could help a lot of PSA cars , not only C6. (AMVAR also in other PSA cars, Hydractive in millions of XM, Xantia, C5 and C6) |
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BillTodd
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 Member No: #1775
Location: Colchester |
I like the app idea  I Discussing the ride quality of my friends 2010 c5 exclusive estate. It seems ok, but well, how do you know? His wife complaints about riding in the back (with their one year old) - she says it makes her seasick. To me there is more bump 'shocks' (as you say difficult to explain!) than I would have expected (not much better than my ancient honda), although the ride is very smooth. An 'app' (I'm of an age where I find such abreviations irritating) could help quantify and identify the problem itself (if not its cause) . How accurate are the accellerometers in a cheap tablet? (I assume they can be calibrated using earth's gravity) Bill |
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Jodyone
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Member No: #1240
Location: Cornwall |
jekkeri- I won't comment on the technical feasibility, as I'm simply not qualified to..! If it could exist, I'd love it. However, even if technically possible, is it even a remotely sound business proposition? C6 is a rare car, and the average age of owners is -ahem- probably approaching the "bewilderment" category regarding smartphones..! How many people would realistically buy this app that you might develop for two platforms? | ||
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