PSI in Airbags?

[~Rich~]

Heh guys,

What sort of pressure is the norm in the suspension airbags?
I thought I heard it was up around 240psi in the reservoir in early D3's before a software update dropped it to around 150psi, is this correct and what is the psi in the actual airbags?

Thanks Rich

[Graeme]

I don't know but my 100 psi tyre compressor pumps-up the airsprings easily - without any load anyway.

[Eurohaus Prestige]

Hi Rich,

When you have IDS connected and looking at the EAS datalogger there isn't any readings for the air bag pressures but only reservoir pressures,

The software upgrade for the EAS module changed the parameters for the time taken for the reservoir to fill to a specific pressure.

Hope this helps any reasons you would like to check bag pressures?

Regards
Wael

[Graeme]

When you have IDS connected and looking at the EAS datalogger there isn't any readings for the air bag pressures but only reservoir pressures

Edit: Snap-shot 1 - both rear valves open, reservoir valve closed, pressure 630 Kpa (91 psi)
Snap-shot 2 - both front valves open, reservoir valve closed, pressure 1278 Kpa (185 psi)

The compressor was running each time so not indicative of airspring pressure. To see the actual pressure, a diagnostic tool could be used to open a valve whilst the compressor is not running.

[~Rich~]

That sort of makes sense Graeme,
The rear airbags would have to have twice the volume of air to the front ones.
Front ones normally would carry more weight than the rears I'd thought, unless you are loaded up with either a Van or trip ready.
The pressure in the rears would go up as required to carry the load.

I've just replaced all my struts with new OEM ones after 8yrs of service, bit of a bugger to replace but I'm sure I've saved a heap in labour costs.

Just wondering what the psi would be in them.

Thanks for the replies.
Rich

[bbyer]

Specifications

Air Suspension - General Specification

Ride height:
Off road 55 mm (2.1 in) above standard
Access - reselectable whilst vehicle is moving 50 mm (1.9 in) below standard


Height sensors:
Location 4 per vehicle - one sensor for each wheel
Height sensor arm colour coding:
Left hand side, front and rear WHITE
Right hand side, front and rear BLACK

Height sensor operating voltages:
Supply voltage 5 volts - supplied by air suspension ECU
Output voltage Left hand front and right hand rear - Decreases to 0.5 volts with bump travel. Right hand front and left hand rear - Decreases to 4.5 volts with bump travel

Spring/damper modules, (the four air springs, one on each corner):
Type Guided air spring surrounding twin tube damper, (shock absorber).

Air Spring Normal Operating Pressures:

Front: 800 to 1000 kPa (8.0 to 10.0 bar) (116.0 to 145.0 lbf/in²)
Rear: 500 to 800 kPa (5.0 to 8.0 bar) (72.5 to 116.0 lbf/in²) Burst pressure 3500 kPa (35 bar) (507.5 lbf/in²)

Maximum spring pressure - Full bump at gross vehicle weight, approximately 2700 kPa (27 bar) (391.5 lbf/in²)

Air compressor:

Supplied with air drier, electrically switched, pilot operated exhaust valve and double temperature sensors, controlled by ECU. Maximum pressure 1680 kPa (16.8 bar) (243.6 lbf/in²)

Air reservoir:

Working pressure 1750 kPa (17.5 bar) (253.75 lbf/in²) Maximum operating pressure 2300 kPa (23 bar) (333.5 lbf/in²) Volume 9 litres (0.31 cu.ft)

Reservoir valve block Incorporates pressure sensor to monitor spring and air reservoir pressures

Valve blocks: Front 2 corner valves, 1 cross link valve - all mounted on front bumper armature
Rear 2 corner valves, 1 cross link valve - all mounted on left hand rear spring tower"

[joel0407]

[QUOTE=bbyer;1928104]
Air Spring Normal Operating Pressures:

Maximum spring pressure - Full bump at gross vehicle weight, approximately 2700 kPa (27 bar) (391.5 lbf/in²)
[QUOTE]


Wow 391psi. And some people replace the wabco pump in Disco IIs with ARB Compressors.

[Graeme]

That's the maximum pressure that the airspring can get to at bump stop at gross axle weight, ie hitting the bump-stops fully loaded, not what the compressor will pump into the airsprings.

Those sensor voltage changes are only applicable to certain model years - other model years have other operational characteristics. That's why Llams must be calibrated to a vehicle once fitted.