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[polilara]

As earlier informed I installed Original GM rear Pneumatic Shock Absorbers to my Sedan to improve height control when e.g. towing my mobile home. To get pressure inside Shocks I connected them to Monroe part seen in pic. As that part is just a "T" I have a feeling that when I (without caravan) drive fast around the corner car tilts more than earlier as air can move from one shock to another. Is original level control so that each wheel has a separate control or are they working together.

[cam.in.head]

looking at the valve in picture its like the one on my carlton. you manually inflate it with a footpump ( or electric inflator etc). the lines put air in both together .

[Doctor Gollum]

The factory Omega B uses a single line to the compressor which splits at a T above the rear axle. So in that respect, to answer your e, it's the same. There's check valve in the compressor to regulate the system pressure whereas the guage/Schrader combo serves the same purpose.

Obviously the factory system is a bit more intelligent in that it automatically compensates for load.

That said, the compressor relay is controlled by the level sensor so retrofitting the factory set up is a pretty straightforward proposal 

[LC0112G]

There's check valve in the compressor to regulate the system pressure whereas the guage/Schrader combo serves the same purpose.

There isn't a check valve to regulate the pressure. There is a valve/solenoid to release air when the level sensor thinks the car is too high. But the compressor can and will run to stupidly high pressures if the level sensor thinks the car is too low. Nothing in the standard setup actually knows what the system pressure is.

Basically, car too low, sensor enables the relay which causes the compressor to run to pump the shox up. Car too high, sensor opens the solenoid to let some air out and let the shox down. I've never opened a sensor up, by there does appear to be some electronics in it to add some hysterysis so the pump/solenoid aren't continually turning on and off over every lump and bump in the road.

[Doctor Gollum]

The electronics all live in the level sensor. The system is designed whereby the pressure is regulated to maintain a predetermined ride height. Obviously this would vary with load. I think it measures the sensor position every 3-5 seconds whilst the engine is running.

Basically, it knows if the car is fundamentally level or not and adjusts the pressure accordingly

It should be noted that it is totally independent of the xenon levelling system.

[polilara]

Thanks for good discussion, DG's first reply answered to my basic question. If factory system really has this T, too, I think it is a stupid construction if I understand this in a right way. When I turn left the right side of the car goes down and I think that the increased pressure in the right shock is flowing to left shock (to balance pressure) and it is lifting left side even higher, which I feel like increased tilting. Perhaps I should install a valve to one of the hoses to make each shock to work independetly. Is this wrong thinking?

[Doctor Gollum]

The suspension was never meant to be adaptive to anything more than rear axle load. I would leave it fundamentally as designed.

Fully adaptive suspension has much more complex control systems.

Trying to recreate that manually has too many variables and when you miss a detail,.you will potentially kill yourself or someone else when the car responds unexpectedly under emergency duress.

The pneumatic system on the Omega is basically thick as mince. Fully adaptive suspension is Albert Einstein by comparison.

Fully adaptive air suspension runs at a significantly higher pressure and each corner is controlled independently based on several thousand calculations every minute using sensors tied into lateral load sensors that are part of both the ESP and SRS systems and adaptive dampers to control s inhock response.

If you're bored, you can always try and retrofit Airmatic and see where it gets you

[LC0112G]

The pipework connecting everything up is very small bore - something like 1.0mm or 1.5mm. When you dynamically load one side or the other by turning in a corner, the small diameter means the air cannot leave that quickly, so there is already a 'restriction' in the rate at which the shox can be loaded/unoaded.

The exact same system is fitted to the Lotus Carlton/Omega, and if there is one thing Lotus know about it's suspension. I've seen a Lotus document which discussed the arrangement, and their conclusion was that it was sufficient for road use, and the best improvement would be to fit a stiffer rear anti roll bar. However, stiffer rear suspension can result in quite a sudden snap-away in cold/wet/icy conditions which for a road car and the average driver becomes irrecoverable very quickly - in other words you wrap yourself around a tree on the outside of a fast corner.

[Andy H]

On the GM air-assisted self levelling suspension the road springs provide some roll resistance and the anti-roll bar provides some more.

I doubt that the air pipe was intended to restrict the air flow. It would be downright dangerous to go into a long, sweeping corner with a car that was planted and discover half way round that the roll resistance had gone.

I wonder if the roll bar on self levelling cars is stiffer than the roll bars on normally sprung cars to compensate for the loss of roll resistance with softer springs?

[johnnydog]

As far as I can see from the EPC, the antiroll bar / stabiliser bar is the same irrespective of which suspension is fitted.

[LC0112G]

The rear Anti-roll bar is the same on all Carltons, Omegas and Senators.

What happens in a corner is air is forced out of the 'loaded' shock and into the 'unloaded' shock, but at a relatively slow rate (because the pipework is so small) so there is no sudden change. The effect is to extend the unloaded shock, so that sides tyre remains more in contact with the road than it would be if it were simply being spring assisted.

It's much more dangerous if both rear shocks pump up to full height/pressure - if say the link arm to the sensor pops off. The rear end goes rock solid. Been there, done that, got the gravel rash.

[polilara]

I believe that if I pressurize the rear side manually to right height and then close both pipes with magnetic valve I have a situation like I had a bit stronger springs and the anti roll bar can do its job. Less tiltig I guess.