I have a shock dyno and have just dynoed my x358 xjr shocks...

https://www.facebook.com/media/set/?...1&l=df18ac09b4




Front Left and right shock, one is obviously broken...

Just my input on this.

Best regard
Ole Mobeck
Norway

 

Hello Ole,

I have moved your post from an old unrelated thread to start your own new thread since your topic is unique and very interesting. Is there any chance you could post a photo or two of your shock dyno in action?

Cheers,

Don

 

Excellent! I was just about to post in another thread that we don't have any shock dyno data.

so 150000km is about 93k miles. Are these both originals?

 

Ole,
Could you say if you changed your shocks preventively or after failure and give more details on your testing (testing conditions and data/units reported in the axis)?
Also in the graph of your link, there is another curve, does it correspond to a rear shock?

 

The shocks should actually mirror the same valving in both front and rear. On eCATS shocks, the profile for un-energized (not plugged in and the vehicle not moving) it will be the "stiff" profile. The vehicle has to reach a predetermined speed before the PWM to the shock will be the "comfort" setting. If the valve is stuck in "comfort" or the valve is damaged, leakage of the internal gas, or other failure, it would cause the difference in the graph above.

 

Hi, I will explain why and how as I know it.

The car is a XJR from 2008 With original shocks, its my car and I have had it for 4 years. When I bought it it had 100 000km on the meter and I guess it have been used mostly at autobahn in Germany by the previous owner.

I drive it all year around up here in Norway and in the summer I take it to the track ocationally. I would say it was sharp and superfine when I bought it but after a trackday where I actually jumped with the car I also weared out the tyres and bougt new cheap ones. This was summer 2015

After this I could not feel anything wrong during normal ethusisatic driving on the road, but early this summer I attended a Autoslalom event and just could not get the presision, and the front of the car (tyres) had a tendency to vibrate/jump/wobble at the griplimit. The griplimit was also too early. I thought it could be the new cheap tyres. As normal driveing the car was just fine. And on a Jaguar its wery difficoult (impossible) to check shocks by pushing th wing/fender.

But right now I put on wintertyres and the car feels just fine, but I am not able to push the limits with these tyres so.. normally i would say its fine.

But then I desided to do a big service on the car right now, Mount a Quafe diff, bigger crank pulley for the supercharger and fix the VVT rattle.. Big job.

So I took off the shocks while I was at it. Easy job, thanks a lot Jaguar.
And these unists are real light, amazeing.

I have to say i am Bilstein Motorsport dealer here in Norway and I have a Shock absorber dyno. So to learn and be able to knoe I took the shocks apart to run them in my dyno. Nice to know if its shocks or cheap tyres that troubles my car. It is not so easy to run the shocks in the dyno with the airspring on, so i took everything apart to ahve full control and also learn.

Many People think they can dyno test a shock and say if it is firm or soft just by pressing then against the floor, but sorry to say it is not possible. The forces and speed you can obtain by that just tell us nothing.

But one thing it can tell us is if there has been any gas leak from the reservoir in the shock, passt the divider piston and into the shock oil.
If so you can hear the Bubbles og past the piston when you press it together form extended as the gas collects at the top. You also feel that there is less force at this point. But these front Jaguar items there is a internal spring that limits the extension of the shock so its a bit difficoult to ectend it fully. But on one of my front shocks I could feel it actually was a little bit gas in the oil. Thats trouble... The other three was fine.

So Into the dyno with them. The dyno measures the force in newton relative to the shock speed in mm / sec.

The vertaical axis on my graph is Newtons and the horisontal is shock speed in mm /second. The compression fore is above the line and rebound is below.
Standard Bilstein measurements has been done at 520mm per second for many years (forewer) If you find a old Bilstein Motorsport shock marked forexample 110/320 it means it holds back your movement at a fores of 1100N at 520mm/sec in compression and 3200N in rebound.
This number say nothing about the lowspeed forces, Witch I would say is below 150mm/sec.

So The two graphs you see is my left and right front shock...
This means the Blue one is ok and the green is not.

These are Bilsteins With the elecromagnetic valve in the piston, to Control these forces as we drive. But in my dyno I run them without this Control (cats) and without Control they are in Firm mode. That is ok with me in the dyno.

The fault we see could be gas in the oil or a open Control valve in the piston.
My Guess is the Control valve. As you can see the force at 520mm/sec is just about the same, and With gas in the oil this would be affected moore I think. But the green line show a moore linear or progressive shock With low lowspeed Control With would be the way to build a comfy shock...

And the blue line had wery high (good) lowspeed control, its wery degressive, and this looks like a race shock for flat nice asfalt.

So I thing this almost represent the difference of firm and soft setting, this means the electomagnetic valve is open on the green shock... I think.

I have not opened them yet, will do soon, I have moore work on the car to finish first.

I include some moore Pictures and a link.

And almost allways on a front engine rwd car the front shocks is firmer than the rear. You can see this on this graph where one rear shock is included. Light blue or maybe turquise..
You can see the compression of front and rear shock is almost the same but the fronts have stiffer rebound than the rear.





Here are the shocks shocks during dismantling




Here a video of my dyno, not with a Jag shock..


If someone know what the Control signal look like I may be able to make it and thes tthe valve... I have heard something like 400Hz and +-5V but I am not shure..? An I need to know that to chage on that Hz or volt to do what. If you know pls let me know.

Ole Martin Mobeck
Forside - mobeck.com

 

The PWM is @ 400Hz, and duty cycles greater than about 50% provides enough voltage to change the electromagnetic coil. Full voltage across the coil continuously can lead to overheating of the coil windings, but for short term testing I doubt it would create a real issue on those taken out of service.

 

Ole Martin,

This is a fantastic job, congrats.
Gives additional insight to understand how these air struts behave and may wear.

 

Ole,

Thank you for your very enlightening work!

I can add some information to David's reply to your question about the ECATS PWM signal, and I hope you will be able to answer a couple of my questions.

First, here's a scope image of the ECATS PWM signal from our member Cambo:



The photo is from Cambo's post at this link:

https://www.jaguarforums.com/forum/x...76/#post544336

Now my questions:

1. Can you explain how to disassemble the shock absorber from the air spring?

2. Some of our members have had to replace air spring/damper units due to a ruptured air spring bladder. Do you know of a source of replacement bladders?

3. Some members have problems with a front air spring leaking at the top seal in cold temperatures. The top seal is a large molded rubber component that fills the area around the top mount plate, which is Part 6 in the diagram below:



Is it possible to disassemble the upper components of the air spring to attempt to apply a sealant of some sort around the top seal?

Thanks in advance for any information you can provide.

P.S. If you don't already have it, you can download the Air Suspension & ECATS section of the Dealer Training Manual here:

http://www.mediafire.com/file/7rdkgg...on_Section.pdf

Cheers,

Don

 

Thanks, and now I see in the ECats training manual that the shock valve has only two settings, open and closed.
Just like the Bilstein B16 IRC aftermarket shocks for other cars, but the Cats are much moore clever in sensing driveing style and the need of switching on and off.