ACTIVE DAMPING

Many modern performance cars now have active damping control systems. These types of system can be known by many different fancy-sounding acronyms, but all are very similar in the way they work, and all have the same goal: to remove some of the compromise between the level of ride comfort on offer and the performance potential when used in anger.

HOW IT WORKS

The way active damping works is very complex in practice, requiring various sensors mounted all over the car and a very clever ECU to interpret these inputs and make sense of everything. But in theory the idea is quite simple when you break it down. Going back to looking at how a monotube damper works, we still have the shim stack controlling the oil flow through the piston, and we still have a gun-drilled hole through the centre of the piston rod.

But rather than having a manual adjuster controlling the oil flowing through the centre of the piston rod (the knob on top of the damper body), this is controlled by electronic valves. This means the amount of oil flowing through the piston rod and therefore bypassing the shim stack can be directly controlled by the damping ECU.

And this is what allows us to have various suspension modes on modern cars. For example, a ‘comfort’ or ‘normal’ mode might see this valve wide open, meaning less oil needs to travel through the shim stacks, giving a softer setting, whereas a ‘sport’ mode might see the valve half-open, meaning only some of the oil can bypass the shim stack, resulting in a slighter firmer setting, while a ‘track’ mode might see this valve fully closed, meaning all the oil needs to flow through the shim stack, giving the firmest setting possible.

It’s not quite as clear-cut as that, though; these valves are continuously being adjusted at fractionof-a-second intervals, and the modes are more of a base setting for how the ECU tells the dampers to respond. For example, the active damping system can respond so quickly it can detect when you stand on the brake pedal and firm up the front dampers to reduce the car’s tendency to dip its nose under heavy braking.

The same is true when you’re cornering and accelerating, resulting in a suspension system that is always at the optimum setting for the conditions.

MAGNERIDE-TYPE DAMPERS

Some active dampers can also alter the settings by changing the physical properties of the oil used. These are known as magnetorheoligical dampers and use special oils containing metallic particles, along with electromagnets to affect the oil’s viscosity. When current to the electromagnet is increased the oil behaves like a thicker fluid, therefore making the whole damper feel stiffer and firmer. When the current is dropped, the oil is free to move around more easily and behaves like a thinner fluid, softening the damper effects.

Active damping systems like these are very good for those of us who benefit from the compromise between comfort and performance, so are ideal for fast-road cars, but seldom seen on out-and-out motorsport machines.