rear air bag suspension

[skauldy]

Guys,

In the middle of fitting disco 2 axles to my def 90. Just wondering what would be involved in fitted the disco airbags. I have on board air and tank but what would be involved sorting out ride height

According to belbins members of a team I'm a plant, so I need the rest of yous to help .

[Snagger]

You'd need the ride height sensors, compressor, valve assembly, air tank, air lines and ECU. It has been done before, but it's not a small job.

You might want to check with your insurers and authorities that they're content with the alterations before proceeding. I'd be surprised if there were any issues witht he authorities, but most insurers get very anxious about even the smallest mods.

[skauldy]

Even though I have the on board air system id still need the disco compressor.

The ecu. Would it work just using the srs end of it or would it throw up errors when it doesn't find other stuff like doors etc

[Snagger]

SRS is "safety restraint system", aka airbags. SLABS is the ECU you'd need; it's a combined ECU for the Self Levelling and ABS.

The ECUs on modern vehicles put the engine into a safety or "limp home" mode when other systems have a malfunction - the ECUs communicate with each other. I don't know if the D2 does that; it wasn't very advanced by modern standards, and I think its ECUs are all isolated. But I'm really not sure about that. However, since your current engine doesn't take suspension inputs, the EAS should work as an independent system - the EAS took inputs from the key remote button switches and ride height sensors only, as far as I understand. However, with no ABS system connected to the SLABS ECU, it might detect that as a fault and refuse to play. Given that you are fitting the D2 axles, and thus brakes, then it may be a worthwhile step to look into how to fit the complete ABS system, which would not only be advantageous in its own right, but would deal with the SLABS too. Hopefully someone here will know the system far better!

[simonr]

It's straightforward enough to implement with your on board air system.

At it's simplest, just use one ball valve between your pressure reservoir and the two bags and another between the bags and an exhaust.

Turn one valve to raise and the other to lower.

You can replace the ball valves with solenoid valves (including the standard Disco valve block - but you'll need to experiment to discover which solenoid does what) Then place switches on the dash for up & down. You can easily wire them to give you a single switch which raise/lower both - plus two which raise/lower just one side to lean the vehicle.

Once you have the solenoid valves, you can make them automatic by placing two switches on each trailing arm. When the vehicle drops below the point where one switch is activated - it allows air in, raising the vehicle and the opposite for the other switch.

You can take this a step further by using an Axle position Sensor from a Disco / RR then switching the valves using a microcontroller. This would give you the option of being automatic as well as being able to adjust the ride height on the fly.

So it's as simple or complex as you want to make it!

Si

[skauldy]

Thanks for all the replies guys

Thanks Si. So with your idea I wouldn't need the disco slab ecu. I could use the hardware and if I wanted build the microcontroller for the fancy stuff. Think I might just get it rolling and come back to this

[simonr]

I built something similar years ago (some on here will remember on one of our trips to Wales) - using a microcontroller + gyro to detect level. One advantage was that it tried to level on corners & side slopes though it used one hell of a lot of air to react fast enough on corners.

I started with switches - and it just evolved into something more complicated.

I've seen a commercial after market kit which just used a pair of mechanical pneumatic valves operated by a lever attached to the centre of the axle. It was very simple - and worked really well. The guy carries a lot of weight in the back of his LR - but it always sits level (and not overloaded!).

Si

[skauldy]

Getting more confident with your post Si. Think I will tackle it with a basic switch with the hope of the micro controller and self adjustment. When fitting the disco axles I thoug hey why don't I see can I fit the airbags as they are great for towing trailers as that's what this truck will be mainly doing with the odd greenlane throwing in. I could also get it to lower then and reverse up and hitch onto the trailer or lower when loading.

[Snagger]

Don't you need separate valves to each air spring to prevent air from one going to the other on corners and cross axles?

[elbekko]

On cross axles, you'd want them to be linked. On corners, not so much indeed.

[Snagger]

I would have thought that cross linking might make the suspension too supple for off road (definitely on road). I know you need suppleness for cross axles, but wouldn't this be too much?

[elbekko]

Look at what the L322's air suspension does off-road

[simonr]

If you want the bags to move fast, you need valves & hose with a big bore. However, you need to control each individually. If not, use small bore (or in line flow regulators). These will allow gradual adjustment and you'll barely notice the cross flow as it happens so slowly.

As a first-fit, you should just put a tyre valve on each air-bag. I kept a kit in the truck to change to this in the event of a failure. Then you just pump them up to the height you want - and can forget about them, just treat them like regular springs. It means you can build the truck - and worry about all the plumbing later.

Si