I have been searching here about this but couldnt find really solid answer. So I will do it here:
Does CATS work with Arnott airsuspension or not really? Is it only Bilstein shocks that are compatible with that system?

 

No and yes.

 

Therefore, if I get this right, it would make less sense to keep the air suspension with shocks that don't work with CATS rather than converting to high quality coil dampers.

 

That is most definitely a matter of opinion and depends on how much you value your Air Suspension. For me, the answer was simple. I have a LHD car here in Dubai which I will not be shipping to the UK when I leave here in the next few years. So, cost of maintaining Air Suspension too high for me? Personally, I have not really noticed any appreciable harshness or deterioration in comfort or handling with my adjustable coilovers (they adjust 15 stops to soft or 15 stops to hard as well as for ride height). But then, that is unsurprising, since the actual oil-filled struts part of my air springs were 18-odd years old and well past their prime?
It's a personal decision. I may have made a different decision if I intended to keep my Jaguar forever?
As an afterthought, I do have to say that I have enjoyed my Jaguar far more since the risk of finding it floored in the morning or bursting an airbag enroute has gone!
I hope this is of some help...

 

I have not doen a big research about it, as I prefer to keep my car original with the air suspension, but the main problem that I see here in Germany and maybe that is a topic in Switzerland, as well, is: are there coilover kits available that do not compromise the road legality of the car, meaning that they have the necessary official certification?

That is an issue for me, apart from personal preferences.

Best regards,

Thomas

 

You are absolutely right, they would need to be approved here in Switzerland also. However, I was making just a general point, as my original air suspension works flawlessly so far.

 

Then let's keep fingers crossed that it stays that way

 

Understood sir, if my original air-suspension was still in place and in a working condition I too would post about it from time to time to let everyone know 😁

I am on air Arnotts. Only later I learned they don't support CATS. But I would've probably gone with air anyways.

 

The Arnott metal spring retrofit works extremely well. It is a bit firmer than OE air system on XJR. Mine has been faultless for the past 60K+ miles. Arnott kit includes air suspension fault defeat board.
I would not suggest any of the cheap Chinese alternatives.
Retaining CATS means OE Bilstein struts, which are NLA for XJR last time I checked. These are a good solution for non XJR cars, but figure $3,500 - $4,000 before labor, plus you may need to renew compressor as well.
I initially went with rebuilt XJR air struts, which was an unmitigated disaster. Wish I'd gone straight to Arnott in the first case.

Hope this helps...

 

Unsurprisingly, I'm confused.

I've replaced two air shocks, both fronts, one 10 years ago and one recently. The first was Arnott, the second was quickly purchased on Amazon...

The up & down leveling seems to work great - does this mean that the CATS is working & these additions are CATS compatible? In each case, both were said to be for my 04 R.

Carpe diem,

Steve S.

 

Very helpful, we'll keep in mind when the time comes. Thanks!

 

Air suspension and CATS are two different things?The air suspension controls the air in the air bags within your air springs and CATS is the electronic control of your oil-filled dampers?

 

Thanks, ESRay.

Oil? What oil? Engine, transmission? Am I supposed to have added or checked the oil in the oil-filled dampers? If so, where is the dipstick? For that matter, where are they?

Thanks, best & GO IRISH!

Steve S.

 

Steve,
Oil-filled suspension dampers have been around forever? A damper is like a piston within a cylinder. The cylinder is full of oil and the piston pushes against and tries to compress the oil within the cylinder and this dampens the pistons movement up and down the cylinder? CATS simply uses an electronically controlled and motorised solenoid to open up or reduce the size of the oil gallery within the cylinder, thereby increasing or decreasing the resistance felt by the piston? A larger oil gallery creates a softer ride and a smaller gallery a firmer ride.
It is a sealed unit; you leave it alone!
The point is that just because your air suspension is working does NOT mean that CATS is still working?
Please can I suggest you read Don B's excellent write up in the stickies? Air Suspension & ECATS System Summary: Components & Operation - Jaguar Forums - Jaguar Enthusiasts Forum

 

Thanks again, ES Ray!!

Such erudition on such an esoteric subject! I will reread and investigate further what you have sent and will delve into Don B's Thread on the subject.

Best,

Steve S.

 

As stated, CATS has nothing to do with air suspension or the car levelling. It's a binary setting in the damping of the shock absorber, soft or firm. Only OEM Bilstein struts have the CATS system. All the aftermarket air struts can work just fine for the car's level and ride quaility, but CATS will not function, as the struts do not have the dual setting. If the CATS is not disabled properly on later XJ8s, you get a permanent ACTS error and yellow LED on the dash. Arnott struts come with the module to clip onto the controller wiring to disable that, and somewhere around here is how to wire resisters into the connectors that went on the OEM struts to activate CATS.

Non-functioning CATS is not deal-breaker, it just means the car won't firm up the shocks when you toss it around.

 

Hi, Steve,
Here is some for your homework:
Traditional suspension
This video describes approximately how CATS (Computer Active Technology Suspension) works. I could not find video describing CATS actually.

Modern advanced hydraulic suspension systems

This is what that never went beyond prototype:
This uses computer and voice coil motor (electromagnet) instead of hydraulic liquid and valves.

There are many different technologies how to make car suspension stiffness adjustable according to driving condition and drivers intentions.

Our cars' original suspension is conglomerate of air suspension, responsible for leveling the car and keeping it at certain height above the road AND stiffness management, this is a binary function: soft or comfort and stiff or sport. The latter is CATS responsibility.
Hope this gives you some clarity.

 

Steve, do you have the XJ 2004 Model Year technical guide? I've attached it below. It has some good info on the air springs.
Your Arnott's won't work with CATS. Not sure why you don't have an error message. The only difference will be that you don't have the soft and firm settings. The shocks others are talking about are on the XKR for example. Magnetorheological. XJ's don't have those.

 

I should have read the guide through myself. The shocks are adaptive, alternating between soft and firm depending on conditions. CATS controls the shocks, ASM (Air Suspension Module) controls the air springs.

 

2004 won't produce the CATS error when the ASM is unpowered. I don't recall if it's 2005 or '06 and up that need an override module, or even mid-'05, Maybe.