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This type of suspension has been popular in America since 2002 – first used by Cadillac, but it looks as though it will appear on more European vehicles soon.
At present Magneride can be found on the Ferrari 599 GTB, the new Audi TT and Audi R8, but don’t expect you see too many of those. However, when you do see a car fitted with magnetic suspension, it is likely to be a Delphi system.
Cars which use continuously adjustable electric suspension systems need electro-mechanical valves, springs and shims as well as motors to allow different levels of damping.
Instead of all this, Magneride uses four single tube dampers which are filled with a magnetorheological fluid. A magnetorheological fluid is one which hardens when placed near a magnet and becomes a liquid again when the magnet is removed. Sensors are fitted to the dampers and these are linked to an ECU.
The fluid is oil-based and contains a suspension of magnetic particles (probably something like iron powder). Each damper contains a coil and electric current can be applied to the fluid by means of this coil.
When there is no current the damper fluid behaves just like any other damper fluid and the piston moves up and down according to road wheel movement.
When the current is switched on, a magnetic field is created which makes the magnetic particles line up and form fibrous structures in the direction of the magnetic flux. The fluid now provides resistance to fluid flow through the damper piston.
A maximum of 20W is needed for each damper and the current can be adjusted to provide a wide range of damping force so ride quality can be changed from soft to hard - almost instantaneously.
There doesn’t seem to be any dispute about the effectiveness of this type of suspension, but it is still pricey. It ranges in sophistication - that fitted to the TT uses a switch on the dashboard so the driver can decide whether he wants a firm ride for hard driving or a softer ride for motorway cruising. Other car manufacturers may select the much more expensive controllable versions with ECU and sensors, to provide a constant smooth ride which adjusts automatically to take into account road conditions.
© Vanessa Guyll, June 08 | 