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From Hydropneumatic to Hydractive 3 | What are the key differences? |
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Stealth
 
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   Member No: #986
Location: Sydney |
Having owned several Citroens from the CX through Hydractive 2 (Xantia) and now the C6, I'm curious about the source of hydraulic pressure and some of the 16 laws surrounding the AMVAR system (what does AMVAR stand for?). The suspension guide, downloaded from the technical documents area, is very interesting and explains quite a bit, but doesn't answer all my questions. Q1. Is the electric pump responsible for powering the hydraulic circuit 100% of the time or only when the engine is not running? In other words, is there a separate mechanically powered hydraulic pump, as with Hydractive 2? Q2. Is there any information available concerning the parameters of the '16 laws' governing both comfort and sport modes? There's an expansive explanation of the rear spoiler's operational laws but I can't find specifics for the suspension. Q3. 'Sky Hook' and 'Road Hook' modes seem to be referred to in some articles covering the C6's two chief suspension modes, but if find this reference nowhere in official Citroen documentation. Is this just journalistic license? Q4. Is one of the key differences between Hydractive 2 & 3 the 'actuator' connected to each sphere or were actuators introduced to Cit's hydraulic systems as computer ECU's joined the club i.e. with Hydractive 1 on the XM? Q5. Does anybody know what the official park position is meant to be? Sometimes, when I pull a door handle, the car will drop to its entry position. Not sure why it wouldn't have dropped to the park position when I get out. Other times, generally after a longer period of settling down, the electric pump kicks in and lifts the car to the entry position. I should point out that I do understand the grand design and intentions of AMVAR i.e. the different heights at different speeds etc. Just wondering about some of the detail. Look forward to your answers. 
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travlician
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  Member No: #350
Location: Paradera |
Hi Stealth, here are some answers: Q1: The C6 is 100% pressured by the electric pump. Q2: The 16 "laws" actually refer to the 16 positions that the value that controls the flow between suspension cylinder and sphere can be in. Q3: Knowing physics, it would not be impossible to have something like "Road hook" or "Sky hook" just by measuring the thing they do. So yes, it seems to be journalistic license (aka nonsense). Q4: The new thing for the hydractive 3 is the actuator that controls the flow capacity between the suspension cylinder and the sphere (the core of AMVAR forgot the frensh acronyms words but they are documented in Citroën's descriptions). Q5: The C6 has it moments to control height: 1) Whenever engine is on, based on computer calculation of speed and road quality (and stationary this is a little higher then parked) 2) Upon opening locks (to it's parking position). As a result, when you leave the car there is some driver/passenger weight upon opening the door, so the car is put in its parking position with this weight present. Since driver/passenger leaves the car, the car will rise and this will not be corrected until the door is opened again. Therefor after parking you will see the car slightly higher than usual and since mostly just driver by 1 person you will see the front relative higher than the rear. My problem is, I know how the software works and I'm very anxious to change it but I don't get the source code to work on it... |
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smihaialex
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  Member No: #1031
Location: Bucharest |
1. No! There's only HP pump  2. The only laws are these: - the rougher the road, the softer the suspension, the better the road, the stiffer the suspension - the lower the speed, the softer the suspension, the higher the speed, the stiffer the suspension - at motorway speeds, and if the road is good, the suspension adjusts the car's height making it almost 1cm lower Note: the stiffness and hardness are not linear and continuous, meaning that it doesn't get softer and softer when the road gets poorer and poorer, and it does not get stiffer and stiffer if road is great and speed increases... Instead, there are predefined intervals (stiffness and hardness steps), and upper and lower limits (it doesn't get softer than x, and it doesn't get harder than y). 3. Most likely yes, either journalistic license, or an overly enthusiastic translation from French. All of the official documentation and tech specs are in French. AMVAR, for instance, which should actually be written AmVar, stands for nothing more than 'Amortisation Variable', which is French for 'Variable Dampening'. And the design is very simple and straight forward - a computer measures the oscillations of each of the front wheels (due to road surface conditions) 15 times per second and adjusts the softness/stiffness accordingly - the higher the oscillations, the softer the suspension, the lower the oscillations, the stiffer the suspension. This is why, sometimes, when road conditions are almost perfect, but all of a sudden a bump or a pothole is tackled, there's tons of noise and some shock on the front wheels (there was no way of predicting that that was going to happen) and no noise and hardly any shock at the back (the suspension has instantly adjusted its softness to absorb that particular imperfection). Benz has addressed this issue on their latest S Class, by also fitting the car with a high res camera constantly scanning the road surface. It is able to detect imperfections in the order of centimeters and adapt the stiffness of the suspension waaay before the front wheels have to tackle them. 4. Actuators are only present on AmVar equipped C6s. (V6's) 5. There's no absolute parking position - there are several parameters that the suspension ECU takes into consideration when setting the height of the car, including but not limited to, car load, parking incline, other priority items running through the BSI. This is why sometimes, when leaving the car it seems not to adjust its height, but when coming back to it the next day, you find it in a different position and upon unlock it does adjust its height Battery tension also has an impact. During winter for instance, if battery tension drops below 11V, the ECU only sends the wake-up signal to critical start-up components, suspension not being one of them  Hope that's what you wanted Cheers, Sam |
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dsharples
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  Member No: #119
Location: Woodbridge |
I'm sure there are some early marketing videos for the C6 which refer to Road Hook and Sky Hook. The ideas do conceptually work. Road Hook = Sport Mode. I.e. a mode that enables to car to optimise itself road-holding/handling. Sky-Hook = Normal. I.e. a mode that optimises the car for comfort. i.e. the car body stays level irrespective the road surface and imperfections, as if "hooked" to an invisible line from the sky. Perhaps the Sky-Hook promise could not be actually realised, and was quietly dropped? The C6 does not really float at some pre-determined distance from the ground irrespective of road surface does it? But I assume that it could technically be made to "float" a lot more than it does? Or was the C6 simply too wallowy/sickening ride when in that mode - or was it unsafe due to weight transfer without the physical characteristics of an anti-dive geometry suspension etc. and it was tuned out - so "Normal" became only marginally less damped Sport" - but just with all spheres generally in circuit to make it feel "softer". Finally, I always think of AmVar as giving you a sphere with a variable diaphragm - and I thought that was the actuator does. It gives you a wide aperture, allowing lots of fluid flow (soft damping) into the sphere or a small aperture, allowing little fluid flow (firm damping), and/or both 15 times a second. So it should be able to give a soft and floaty less damped ride, or a firm and fully damped ride - which the XM really couldn't. The XM was always firmly damped unless you played around with the spheres. I used front ones with wider diaphragms to give a more floaty ride, and used saloon rear spheres on the estate rear... The irony is of course that we all had our C6 suspensions updated to "stop the rock" which I think also removed a good bit of the "float"... |
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Stealth
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Member No: #986
Location: Sydney |
Gentlemen, You certainly are a well informed bunch.  Thank you @Travlician, @smihaialex and @dsharples for taking the time to give such detailed answers. Travlician - your description of the parking position and its variability makes perfect sense. I now understand what causes the differences I observe.  smihaialex - what a pity Citroen didn't choose to put high res cameras to scan the road ahead rather than the lane change driver alert system (which, sadly, is de-selected for Australia... we must have different white lines).  dsharples - I suspected the AmVar actuator system worked that way so thanks for the confirmation. How cool would it be if we could see exact details of suspension settings being displayed, live, on the main display! 
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C6Dave
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  Member No: #1
Location: Northumberland |
Stealth wrote ... smihaialex - what a pity Citroen didn't choose to put high res cameras to scan the road ahead rather than the lane change driver alert system (which, sadly, is de-selected for Australia... we must have different white lines). I suspect that most owners that have cars with Lane Departure (like me) have it switched off anyway as it's very annoying in everyday driving. Don't forget the original design spec for the C6 is now circa 10+ years old so 'high spec' cameras would be prohibitively expensive at the time. Be interesting to see how they actually fair on Northern EU roads over time. I suspect they will have as high a failure rate as LDS sensors
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dsharples
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Member No: #119
Location: Woodbridge |
I think this explains it well: - Click Here - And even mentions Sky-Hook and Road-Hook! |
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smihaialex
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Member No: #1031
Location: Bucharest |
Yes! I had seen this particular video... I think it describes more what they wanted to achieve, rather then what they have actually acheived. It's still one of the best designs in the World, but it would have severely benefited from bigger spheres, more suspension travel, and a road scanning radar or camera. I will at some point in the not so distant future change all spheres and AmVar actuators, to bring the suspension as close as possible to its brand new state and see how the ride compares, but I doubt it will be any less noisy when tackling potholes, or that the promise of effortlessly glinding absorbing all of the road's imperfections will become more of a reality rather than a goal, but we'll see... | ||
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Tjensen
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 Member No: #954
Location: Bergen |
Agree with smihaialex. Bigger spheres and longer travel would be better, but probably difficult to achieve with the PSA plaform restrictions. But, I think the TopGear test on the horserace-track is saying something about a good result of the design ! (YouTube). Remember, the DS did not like potholes either. Probably the lack of rubber bushings and the radial tyres made sound and small sharp obstacles transfer through the construction. The CX was better, with the whole chassis isolated from the frame with a number og rubber cushions. And the XM introduced adaption to different driving conditions. We want DS wheel travel and spheres, CX isolating tehcnology and XM/C6 adaptive suspension set-up and electronics ! And why not add Activa from Xantia, then we will also have the worlds' best stability in sharp cornering, |
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travlician
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Member No: #350
Location: Paradera |
I used Lexia (diagnostics tool) on a 10" net-book to monitor the suspension parameters (like actuator setting, stiff mode, ride height). If you find a VGA to composite interface you could link it to the car screen (or find a small laptop with composite video output). Honestly it takes too much attention to be driving safely... | ||
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smihaialex
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Member No: #1031
Location: Bucharest |
Indeed, the Top Gear horserace track stands On poor roads, the ride is unparalleled. I haven't had a run at it in the 2013 Benz S Class with Magic Body Control, but still, I think ride quality in such poor conditions is great in our French presidential limousine. It's the sudden pothole on otherwise perfect road that the C6 has issues tackling!!! And this is why I'm a bit unconvinced by marketing statements such as "effortlessly gliding along and absorbing all road imperfections...", but otherwise, it is a great riding and handling car... When I remember the Top Gear horserace track episode featuring the C6 and the BMW 5 Series (or was it an M5?!?), I can't help but think back to my previous 2010 5 Series BMW (a direct competitor and a car that cost almost the exact same price when new at +/-65,000€)... I kind of did my own version of this test, and there's absolutely no comparison. And not just in terms of riding and handling, but on every front. At the almost exact same price: - engine: C6 - refined 2.7 twin-turbo 200 BHP diesel V6 vs 5 Series - basic, noisy 2.0 inline 4 160 BHP diesel (not even a diesel Skoda Octavia vibrated that much at idle) - transmission: C6 - smooth 6-speed electronic autobox vs 5 Series - clunky 7-speed electronic autobox (the car would effectively jolt on switching from P to D, or when downshifting - it would always behave much like the C6 autobox behaves when in Sport mode) - equipment: C6 extras vs the 5 Series: HUD, TPMS, LDWS, Hydractive 3+ Suspension, Directional Bi-Xenon Headlights, Memory Seats, Heated Back Seats, Sunroof, CD Changer, Phone, Video Mode, Diffused Climate Control and possibly more that I can't remember of the top of my head... - trim: C6 - lush full leather interior vs 5 Series - rather dull leather-velour mix - wheels: C6 - superb 18" drug dealer alloys with 245/45 tyres vs rather common teutonic design 16" wheels w 225/50 runflat tyres - design: C6 - fit of a presidential saloon vs 5 Series - anything but presidential - ride & handling: C6 - one word to describe it - smooth, even though a bit noisy when encountering the odd pothole (you can hear it, but it doesn't scar your kidneys) vs 5 Series - solid & sharp, but very harsh (you could feel every crack in the road in your hands via the steering wheel, in your lower back via the hard seats, and at the back of your head via the headrests - maintenance: despite its Sybaritic luxury, C6 parts & labour are on par with other regular cars, even less expensive than most (in Romania, they are the 3rd least expensive after Fiat and Skoda, waaay less expensive than Ford, Honda & Renault) vs the 5 Series where everything is priced like it comes in a package with a golden nugget) It is and always will be a complete and utter mystery to me, how come, during it's lifetime, the C6 got outsold tenfold by the 5 Series in its home-country of France, and probably even more so in other countries!?! It just goes to show you that when buying cars, most people tend to overlook hard facts like the ones above, and go for badges like crazy regardless of the real value (or lack of), much like when buying designer jeans Regardless, getting back to the subject at hand, why I may feel that the marketing videos represent a bit of an over-promise, I don't for a second lack appreciation for this amazing feat of technology called Hydractive 3+ AmVar, and even more so for the amazing packaging it comes in - the Citroën C6. Cheerios, Sam |
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C6Dave
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Member No: #1
Location: Northumberland |
smihaialex wrote ... It just goes to show you that when buying cars, most people tend to overlook hard facts like the ones above, and go for badges like crazy regardless of the real value (or lack of), much like when buying designer jeans Regardless, getting back to the subject at hand, why I may feel that the marketing videos represent a bit of an over-promise, I don't for a second lack appreciation for this amazing feat of technology called Hydractive 3+ AmVar, and even more so for the amazing packaging it comes in - the Citroën C6. Shhhhhhh, you'll make everyone want a C6 and drive prices up  |
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Rettopian
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 Member No: #1195
Location: Wiltshire |
I don't mind prices rising......... | ||
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smihaialex
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Member No: #1031
Location: Bucharest |
@R: You wanna sell yours, I take it?!? Regards, Sam |
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Rettopian
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Member No: #1195
Location: Wiltshire |
Tempting......... | ||
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