ADS electronics

ADS electronics consists of switches, sensors, wiring harnesses, ECU and acting elements - solenoid operated valves. It is independent of the rest of the vehicle in terms of functionality. You may extract ECU and the vehicle will drive. In the firmest settings and without the possibility to change the ride height.

System consists of the following main components.

Steering sensor

The sensor is mounted in the steering hub and is sending information to ECU. This signal is part of a decision on which corner of the vehicle should be stiffened. It is needed to re-set its values after you disconnected the battery. The ADS MIL in the dash will be lit. Swinging from lock to lock will cure this.
Sensor (N49) consists of hall sensor (b) and plastic ring (a) with magnets (c) embedded.

Acceleration sensors

Two sensors are in the vehicle.

1. On right front wheel hub (B24/1)- This sensor gets vibration from wheel in vertical direction. Its working span is +-12g acceleration.

2. On left front rail in front of damper (B24)- This sensor gets vibration from car body in vertical direction. Its working span is +-1.6g acceleration.

Oil tank level sensor

Senses the level of oil in the reservoir and warns the user if the level drops under a certain minimal volume. It does it via liting dashboard MIL.

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Wiring harness

Wiring harness is connecting all electrical components of ADS. It also brings other relevant signals from other systems to ECU. Main connector has pinout as I checked and can confirm is correct. The issue is that there is a mixup of pinout in variable documents on the web. Mostly mixing in various wiring diagrams from ADS I and II. Also, I have not seen any pinout or diagram with ride height leads.

ECU (N51)

The brain of functionality is enclosed in an aluminum box. For me is unknown how it operates. Since both acceleration sensors are measuring vertical acceleration, these should be responsible to say if the car should soften on harsh road surface, but the softest setting is the default... It is not very sensible and ADS II do not have this configuration of acceleration sensors. There are two on each front rail and one in the back.
The speed value from ABS with steering angle value can be responsible for stiffening outer dampers for anti-roll measures during cornering. That is my guess only.
Is then there any way how the vehicle prevents diving during braking and raising the front during acceleration? The passive leveling is not so quick, that I can see. Again, the ABS speed signal can be used here in derivation as acceleration in the longitudinal direction. That is said in some MB materials.
Another unknown topic is, how two valves of damping valves are working. Are they meant to be soft (both open), some intermediate 2 softness stages (first only open or second only open) and firm (both closed)? Or, as in one material I read, that one valve is choking during compression and second during rebound? That is important to know for my planned My ECU stage 3 build.

Solenoids

Damping valves (Y51-Y54) For each corner there is a damping valve operated by two independent solenoids inside. That allows different settings in damping vertical movement of a given wheel.

Driving height valve (Y36) Two-way solenoid that operates valve allowing flow of oil to link cylinder to one or other side of them. That prolong or shorten the link between the torsion bar and levelling valve for increased or lowered drive height of the vehicle.

Driving height blocking valve (Y37) One-way solenoid that is opening passage of oil from link cylinders in high ride level. After the ignition is switched off this solenoid is de-energized and the internal spring will close the valve. That assure that link cylinders high side (remember that front and rear link cylinders have the opposite ways of acting) do not loose their state. Since leveling valves are just mechanical means, a change of link cylinder length will actuate levelling valves and thus lower the vehicle right after the engine is shut down. That is because of spring in link cylinder pistons will get pistons to theirs non-pressurized state. This solenoid is connected to vehicle voltage directly, not via ECU.

My ECU

I explained on the front page that my system does not work for (to me) unknown reasons.
I decided to make an alternative ECU allowing switching between soft and firm settings via centre console switch (S45/1). This is a momentary switch sending 12V to contact 25 for firm (upper) and 26 for soft (lower) spot of the rocker switch.

I initially wanted to do that with an ordinary relay but you need to keep its state and S45/1 is momentary switch. So there is a relay called latching or bi-stable which stay in its state after you release switching voltage. I needed one operated by 12V and capable of switching 8A. Since every valve has a resistance of both coils in series 12Ohms giving 1A for each damper valve. That means 8A for all 8 coils. The chosen latching relay is in reality quite subtle. So I decided to include an ordinary automotive relay which will be operated by the latching relay.
And so I modelled encasing copying interfaces of original ADS ECU and male connector. Initially, I wanted to source the original AMP connector but no luck here.

For build is needed following:
- 3D printed enclosure - model
- 3D printed connector plate with frame for relays - model
- two screws for plastics to fasten the connector - BS 15858 3137739
- flat wire terminals - pic ebay
- latching relay DK2a-L2-12V
- power relay - relay which fit in enclosure VW 646 PN 4H0951253C
- 2 mini blade fuses - option for extra security 5 or 7,5 A
- female fastons 6.3mm 2pcs, 4.8mm 2pcs, 2.8mm 4pcs

The wiring connection is simple and visible in the diagram.

My ECU Stage 2

I scratched several times ground with my SL underbelly (actually exhaust catalyser). So I want to bring back ride height increase on drivers command in cases the road is rough.
I will replace the link cylinder with an electric linear actuator. There are 12V operated actuators with the right dimensions and stroke. I choose 50 mm stroke and the highest force. The reason is that the enviroment is harsh and the longevity of the actuator is questionable. Higher load capacity actuators have also slower speed. So gearing should be more durable.
The actuator has nearly same length as link piston (I measured 108mm) so just needs to figure attachment.

To operate it, you need two SPDT relays in this connection. Each relay will be controlled by each side of the rocker switch (S77) left to the light switch. That means you can have any ride height between min and max according to how long you hold the rocker switch. And again since the rear link cylinder is mounted above levelling valve and acts in reverse to the front, the rear electric actuator must be connected in opposite polarity as the front one. That also means that rear actuator is fully extended when car is in the lowest position. The actuator has internal limit switches, so should not be overloaded by holding the switch after the actuator reaches its limit.

For to get the signal to the front actuator I will use the wires for energizing solenoid Y36 connected through MyECU to switch S77. There is a box with two relays which will be powered by voltage from blocking valve Y37.

This way can be height adjustment incorporated into NA vehicles without this functionality. Only there is a need to install toggle polarity reversing momentary switch in reach of the driver. And it can be connected directly without the need for SPDT relays. If you do not want to route cables from the dash mounted switch there are wireless controllers available. Of course you need to source 12V anywhere close to rear or front actuator and then route wire to second actuator.

My ECU Stage 3

As I mentioned before, it is not well known how the ECU handles switching valves. And I want to bring back its functionality.
There I checked how complicated would be to attach and read data from the modern accelerometer. It is very easy and the hardware is cheap. Take in Arduino nano and accelerometer MPU 6050. You get it for 6-10 € both and here is how to connect them and the code associated. Piece of cake. Another option is Arduino board with intergrated accelerometer like Arduino Nano 33 BLE Sense. But that is little costy. On the output there can be 3 or 6 relays (in special board, Arduino cannot operate them directly) or preferably MOSFETs. Rear axle valves are switched together on both sides. So the only question is if it makes sense to switch separatelly 2 internal valves in each valve body.

That is the question I am not sure how to check. ADS II manual on pages 108-112 speaks about different choking in pressure stage and tension stage. Which means during bump and rebound.

ADS tech page just speaks about 4 stages of firmness not speaking about the direction of oil flow.

Note that cross-section of damper valve on web page and in ADS II manual differs. Also in some materials damping valves looks that they have input and output on oposite sides. My valves definitelly looks like the one on picture right here. The only option seems to me to go to a shop that is capable to test dampers and measure my vehicle with different valves switched on or off to see what is really done by these valves.

The idea is to make a firmer corner where the load is transferred. In acceleration stiffen the rear axle, during the braking front. At a certain speed to stiffen outer dampers during cornering. Another topic is to incorporate speed sensing from ABS module if that is even needed. Original ECU has no means how to get known lateral acceleration except computing from vehicle speed and angle of steering wheel. With omnidirectional acceleration sensor are these redundant. But for security might be good to lower the car at some speed as in original. That might be sensed from ABS too.

Will it be worth it, I don't know, but it might be interesting to see. Also in spite of prices of acceleration sensors, steering angle sensors, or even faulty ADS ECU that might be worth checking for future proof our vehicles with all their functions. Not to speak about tailoring adaptiveness to personal favors. For example for vehicles with different tire sizes.

Here you can see simulated connection and code. The LEDs are simulating valves. After you start simulation (green play button) you need to click on the small blue board (accelerometer MPU6050) and you can simulate accelerations with sliders. X for longitudinal and Y for lateral acceleration. Also, there are buttons for SPORT mode and for raising the vehicle. That is for my version with electric actuators, with an easy change of code it may control Y36 valve to operate link cylinders.

Function

General info.

Hydraulics

Here is information about function of hydraulic components and some work done.

Electronics

Here is information about function of electronic components and some work done.

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