Re: SLS - system description available? (archive)

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The SLS system consists of a controller, pump w/ release solenoid, storage tank, dampers, accumulators, and hoses. It also has an adjustable rod which attaches to the rear sway bar.

The pump forces fluid into the accumulatosr (and thus into the dampers) to raise the ride height. The pump solenoid releases fluid pressure to lower the ride height.

The "damping" function is not in the shocks - those aren't sealed units. The shocks have a fluid couping (a hose) to the pressure accumulators, which have diaphragms with nitrogen gas behind them. The fluid is incompressible and provides effectivly a variable-length shock, with no pesky metal..the full damping work is done inside the accumulator, by compressing the nitrogen gas under the diaphragm.

The control module has 2 signal wires. One for "pump", and one for "open solenoid". When the controller determines the ride height is too high, it energizes the open-solenoid line to lower the ride height. When the controller determines the ride is too low, it activates the pump line and the pump starts filling stuff up.

The controller is triggered by a potentiometer type device (basically reads the degree value of a shaft). This shaft has a 1.5" or so lever arm attached to it. The rotation of the shaft indicates the ride height and is the controllers primary "sensor" instrument it uses to make decisions about energizing the raise or lower signals.

The lever arm is attached to a 10" or so rod. This rod is attached to a pivoting lever arm, whos terminus is a C-clamp that attaches to the rear sway bar. If the rear sway bar rotates, the C-clamp and lever assembly rotate with it. This moves the 10" rode and then rotates the lever armattached to the potentiometer in the controller.

Thus, it is the angle of deflection of the rear sway bar (measured slightly to the drivers side of centerline) that determines the main input to pump activator. Danial tells me that the controller also has a mercuery switch which only lets the controller send adjustment signals when the car is on level ground and "relatively" still.

Finally, since the rear sway bar is attached to the rear subframe , and has lever arm ends which attach to suspension arms, as the rear suspension deflects, the rear swaybar rotates.

Thus the ride height changes the deflection and rotation of the rear sway bar, changing the degree of rotation of the two lever arms (via their connecting bar) and fnaly making a chnage in the rotational value of the controller input.

Understanding how the inputs generate the outputs means some fun things can be done with sls. You can adjust your ride height in a pinch by unscrewing the C-clamp where the final lever arm attaches to the rear sway bar. Rotate the lever and the input shaft on the controller rotates as well. With the key in the ignition and set to "run" (but starting is not necessary) the car will pump up or lower itself to try and get tot eh correct "position". You are effectively "zeroing out the scale" when you do this.. which may or may not be ag ood idea.. the controller may have a non-linear function to describe shaft input vs ride height.

Also, since the signal from the controller to the pump is just voltage on or off, on 2 different signal wires, you can do interesting things there. Danial has setup his car so that he can leave the SLS in "auto mode" where the SLS works normally, or he can "assert" the raise and lower signals at will to manually raise or lower the car. The rear clearance is very impressive with the shocks fully extended. I saw 6-8 inches of space between the tire tops on the bottom of the fender lip over the rear wheels highest point.its very easy to get all the way under the rear of the car. Not that thats a good idea since your SLS may leak or what have you, but its at least possible :)

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