Electronic Dampening... How does it work?

[nort0188]

Does anyone know exactly how the dampening is adjusted on vehicles with electronically variable suspensions? I know the computer uses all the sensors and such, but what goes on inside the shock itself to change the sizing of the valves?

[Pineapple]

Sturt are like hydrulic cylinder, they got a piston moving up and down. There are holes/valves on the piston to let oil pass. Damping is control by hole/valve size and oil thickness.
Electronic are like manaul adjustable, you turn a knot to adjust valve size. Electronic use a step motor to turn the knot. You can't really change spring rate but with sensor monitoring speed of the piston movment, a computer can control how fast the spring compress and extend.

[nort0188]

Yes, but HOW does the valve size change? What goes on inside when you turn the shaft?

[Pineapple]

Say you got two plate with 4 holes on them. You put the plates on top of each other and rotate them so the holes line up. You got MAX flow at the point. You rotate one against the other and the hole got cover up partially until they're totally block.
The rod on adjustable are tube outside and anothe shaft inside. Outside tube is fixed and inside shaft is used to rotate a plate to adjust hole size.
Another way is to use solid piston. Oil doesn't pass through piston at all but go through tube to flow from bottom of cylinder to top. Like a cylinder with both port connected with a hose. You put a valve on the hose to control flow. Some sturt have twin tube body instead of valves on piston.

[88 LE]

^ Think of a circular disc with holes in it.

As the shock/strut is compressed the piston moves up. The oil within the shock/strut flows thru the holes in the disc (the thing I mentioned above). Same thing happens on a rebound stroke too.

You can control how much oil flows thru the disc, by changing the size of the holes. This changes the dampening.

[nort0188]

Does this same process apply to vehicles with continually variable shocks? Like the new BMW's and such?

[Pineapple]

Most likely. Real CV need electronic.
They also play with the cylinder body. Some oil is pass around the piston. The make the cylinder bore different diameter at different spot to allow different flow rate. Most make the bore taper, top is smaller then bottom. So as the sturt compress damping is increased.

[nort0188]

Awesome, thank you guys very much. Feel free to add anything more.

[ILLICITDRIVER]

impressive stuff.