Thread: Disco 2 SLS Resurrection. Help needed.

Originally Posted by joel0407

Yeah, I want to know how it works because I'm slightly modifying it. My compressor has had the possum. Firstly I'm using a different compressor, it'll feed a air tank that will feed the SLS system. Using another compressor has been done before and nothing new but fine details are not defined. Knowing how the system works will help me getting it closer to right with the first setup.

Happy Days.

If you want to have an air tank feeding it, then the air tank will need to have a one way valve (eg Schrader type) to the SLS. This is so that when the solenoid operates to allow air in, if the air tank pressure is below that required to lift the car (about 70 psi I believe), then air won't bleed out, making the suspension lower.

Then you will need to have an air solenoid that operates via the power feed for the current compressor - shouldn't matter what resistance it is, as it will only be there to allow the air into the SLS.

You will need to have a new exhaust solenoid that matches the resistance of the current one, so that SLABS ecu doesn't register an error and shut the system down (Don't know if this will occur, read it in another post about changing to a new compressor). This solenoid is required, as I assume that you are removing the current compressor, so you will need to emulate the current exhaust setup.

You should have a receiver dryer prior to the air tank, or between the air tank and current SLS manifold (middle inlet between the left and right outlet solenoids), so that the air going into the SLS hasn't got too much moisture in it. That is what the big cylinder on top of the compressor is for. Full of silica to remove moisture from the air.

One last thought, if the air pressure from the air tank to the SLS is too high, then it may cause some problems, as the compressor slowly introduces more air into the system compared to an air tank, so pressure doesn't build up too quickly.

I recently installed a complete manual airbag system in the D2. I got all the goods from Air Ride in Melbourne.

Basically a compressor feeds a tank with a 150psi pressure switch. The tank feeds a valve block which in turn feeds both bags and allows exhausting. Inflation/deflation of the bags is controlled by 2 switches and there is also a guage on the dash to monitor the pressure in both bags.

I am really happy with it and everything works well.

Originally Posted by walker

I recently installed a complete manual airbag system in the D2. I got all the goods from Air Ride in Melbourne.

Basically a compressor feeds a tank with a 150psi pressure switch. The tank feeds a valve block which in turn feeds both bags and allows exhausting. Inflation/deflation of the bags is controlled by 2 switches and there is also a guage on the dash to monitor the pressure in both bags.

I am really happy with it and everything works well.

I'd like the SLABS to do the adjusting for me but if it doesn't work for some reason then this will be my plan B.

My Disco had springs with helper bags installed prior to my ownership.

Happy Days.

Ok, Ive ordered a RAV CD 2 from Dave and in the mean time found an online copy.

It states:
"When SLS compressor operation is required, the ECU provides a battery supply to energise the SLS relay located inthe engine compartment fusebox. When the relay contacts close, a 12 V supply passes through fusible link 9 in theengine compartment fusebox, through the relay contacts and operates the air supply unit compressor. The ECU willthen supply power to operate one or both air control valve solenoids and/or the exhaust valve solenoid to inflate ordeflate the air springs as required. The compressor does not need to be powered to deflate the air springs."

So still clear as mud.

So the compressor will run and either or both air control valve solenoids and the exhaust valve solenoid to inflate ordeflate the air springs as required but the compressor doesn't run to deflate the air springs? WTF

Now I really want to know just becuase I'm an inquisitive bastard.

As there is only a single line feeding the LH and RH air control valve solenoids, the system can only imflate or deflate but not both at once. So what happens when you back one wheel up onto a stump and one side is low and the other high? It cant inflate the compressed air spring on the wheel that is parked on the stump and deflate the wheel that is hanging down both at the same time. If it does one then the other, then the first one will be wrong again and it would get into an infinate loop. So how does it work?

Happy Days.

I think you will find that it is a bit more complicated inside the valve block. It will allow one side to vent while the other side inflates but you would have to get a diagram of the valve block to see how it's done.

However, after saying that I don't believe that the system works as quickly as you are implying. It won't change levels when you drive into a tree etc. It is really only to level up the back when the load in the cargo area changed such as loading up the back when going camping. The crossed linked system used in the Range Rover works more the way you were describing.

Originally Posted by walker

I think you will find that it is a bit more complicated inside the valve block. It will allow one side to vent while the other side inflates but you would have to get a diagram of the valve block to see how it's done.

However, after saying that I don't believe that the system works as quickly as you are implying. It won't change levels when you drive into a tree etc. It is really only to level up the back when the load in the cargo area changed such as loading up the back when going camping. The crossed linked system used in the Range Rover works more the way you were describing.

Since the exhaust valve is on the compressor and there is only one line running to the valve block, it just isn't possible for one side to vent while the other side inflates. If you check my first pic, you'll see I have had this thing a long way apart.


Yep. I know it doesn't change very quickly. I was just using that as an example. Here's another, I load something very heavy on one side of the vehicle. Obviously the diagonal front side will rise and the side with the load will drop. Now what? I expect over a short time the vehicle will level.


Now after the vehicle has levelled. The side where the load is sitting will have higher pressure than the side without the load.


Now I move the load to the centre because I realise its loaded uneven. The side that previously had no load is lower than it should be because the pressure is less than required to level the vehicle. It's side needs more pressure. The side that previously had all the load is higher because the pressure is higher than required to support the now reduced load on that side.


Happy days.

There is one line from the compressor to the valve block, and one line from the valve block to each of the bags. It is quite simple for the valve block to divert the compressor to one of the bags, while diverting the other line from the other bag to atmosphere. That is what a pneumatic solenoid valve does.

Originally Posted by biggin

There is one line from the compressor to the valve block, and one line from the valve block to each of the bags. It is quite simple for the valve block to divert the compressor to one of the bags, while diverting the other line from the other bag to atmosphere. That is what a pneumatic solenoid valve does.

Negative. There is a seperate valve for exhausting air.

The from RAV, air goes one way when raising the bags and moisture is absorbed by some sort of beads, then air passes the opposite way when air is exhausted and helps keep the beads dry. If that makes sense.

So air to and from the bags must go via the single line that feeds the valve block.

Happy Days.