If you remove the plugs it goes to firm.
Its a trick used on track days to lock the shocks in Firm mode

Im not sure if there is a difference in the shocks used on the comfort vs sport unit though. Id guess the rates are harder in the sport ones to ho along with the higher rates on the airbags but don't know

Cheers
34by151

 

As far as I have been able to determine, the Jaguar/Bilstein air springs/dampers do not use magnetorheological fluid. Jaguar's CATS and ECATS systems appear to be adaptations of Wabco's CAS and ECAS electronically-controlled air suspension systems. The air suspension schematics in the X350 service manuals are obviously taken from the ECAS publications. Here's an example:

http://www.google.com/url?sa=t&rct=j...93990622,d.b2w


Wabco refers only to "active dampers," so we're not given any clue as to whether the system is designed for shocks that use magnetorheological fluid or other technology, but your thought that they may just be electronically valved would make sense.

Cheers,

Don

 

Good info! Thank you for sharing. Time to cut the shock to sort out all the guesses

 

The attached may be of help.

 

u102768,

Thanks for chiming in! That excerpt from the training manual is perfectly relevant and seems to confirm that the dampers have electrically- or electronically-controlled valves, rather than using magnetorheological fluid.

Looking at the diagram in your link, there is a "pump rod" labeled near the bottom end of the damper (rightward in the diagram), and a pump chamber higher up (leftward in the diagram). There appears to be an even narrower rod that passes down the center of the pump rod. Is it possible that it is this narrow rod that is controlled by the CATS solenoid at the top of the damper shaft, which opens and closes the Control Orifice to control the flow of fluid and thereby adjust the damping rate?

What do you think?

Coupled with reyesl's dissection photos, I think this may be the closest we've ever been to understanding the operation of this suspension!

Cheers,

Don

 

After surviving the explosive dissection of the strut and studying the document that u102768 posted, I might have an idea of how the fluid is controlled.

The strut had a combination of gas and fluid, gas in the lower section and fluid in the upper section. As the outer metal tube was cut, the fluid sprayed out as was expected, I was prepared and had the band saw covered. As the blade made its way to the other side, the gas propelled the shaft and innards about 50 ft out of my shop and I was holding the metal tube.....I was not prepared for that! Sounded like a rifle!

The lower section filled with gas might be an accumulator, not sure on that as there were no bladder material present. There is a valve screwed onto the electromagnet with a disc that moves, the disc is what most likely controls the flow of fluid. When voltage is applied, the disc is drawn toward the electromagnet and thus uncovers 2 ports. The disc is pushed back by a spring, covering the ports in the absence of voltage. No voltage, the strut is in the default or hard mode.

 

Wow, we're very happy you were not standing in the path of the spear when it fired!


Could the diaphragm material be thin metal?


I think you've done it, reyesl! You've explained how CATS works! If I'm not mistaken, your actual shock does not conform exactly to the diagram in u102768's document. I'm not surprised, since the actual shocks also do not conform to the cutaway view of the air spring/damper in the '04 New Model Introduction Dealer Training manual that I have.

Thanks for all your hard (and dangerous) work on this!

Cheers,

Don

 

Yes, thank you reyes! I guess this is the simpler variety of active shock after all. That valve just switches the orifice size giving firm/soft shock action.

This also may explain why owners who abandon the CATS shocks for passive see only a marginal difference... on the Cadillac with the MagneRide if you lost that system (with fully variable shock control) it was readily apparent.

 

I can see now why Arnott only replaces the air bladder portion of the shock and not the gas/oil filled strut portion on a rebuilt air shock. Great surgery job Reysesl.

 

I clamped the rod on the band saw, turned it on and nothing! Just a light scratch, I forgot that the rod is normally made of hardened steel! Oh well, I got it with the chop saw.
The brass electrical prongs go through the rod into the “Electromagnet” where a “Copper Wire Coil” is energized, thus controlling the movement of the disk which in turn varies the flow rate of the fluid. I am wondering if the gas acts as a damper, hmmmmm?
We need a little input from the fellows at Bilstein, Jaguar, Arnott, and Strutmasters!

 

Arnott replace the spring. similar to replacing a broken coil spring on a McPherson Strut unit. Clearly the unit is examined before the new air spring bladder is put on. Any leaking unit is scrap, obviously. I would think the shock electrical contacts are tested for continuity too. Bilstein are a quality manufacturer, not a Joe Noname operation. I have a set of Bilstein monotube shocks on my MG TF.

 

This is standard on nearly all shocks since since the '70s. The gas charge prevents the oil from aerating and loosing its ability to dampen.

 

Come on now, I am trying to get input from the factory....

 

Impressive piece of work. Hats off to reyesl for all his work and all the others who chimed in with their knowledge and information!

Guus

 

This thread needs to be a sticky, it's too valuable to get lost on the list.

 

More photos:



The Dividing Valve separates the Oil and Gas (usually nitrogen), the gas keeps the oil under permanent pressure which prevents foaming/cavitation. The seal appears to be rubber.






The Anti Cavitation Valve, along with the washer combinations, prevent any further cavitation/foaming. The seal appears to be made out of Teflon, similar to the compressor seal.



I believe Bilstein developed the gas pressurized shock for the Mercedes back in the late 50s. I would like to see a cut-away illustration of this strut assembly from Bilstein........

 

Thanks for all the great info. Any way to get some oil on the leaking bushing at the top to cause it to swell? Maybe trans stop leak oil possibly. Anyway I have an Arnott rebuilt front leaking after a 2-3 years. (bought the car recently, 125k mi 2004). Weather warm but just started leaking out of the top center hole. Don't have it off yet.

 

As a new member I found this older Thread extremely helpful. Thank you

 

Reyes! Thanks for all of your work to exposed the air shock components, but looking forward to the companies for input is like snow in the mid Summer, they don't want us to know the secrets, some one might find out the way to fix it themselves, they want you to go buy their parts from the dealers.
Do you think pump the green goo-is stuff like the tire seal in the air hose connector to (not cured) slow down the leak, until the new units is replace? Just a thought. Thanks for all your work and pictures again.

 

Alien artifacts decoded!