All datas on this page take the 99' Discovery as an example. Freelander models and Defender systems are quite similar though.
This is a development by Land-Rovers own engineers. Basically it's an system that controls body roll and adjusts the suspension accordingly. For the moment it's still available with air suspension or solid coil springs- maybe a better choice for greenlaning.
The ACE works only on the torsion bars.(Above-rear, below-front)
This picture shows the front setup. The system works on the torsion bars, forcing the outside wheel to the ground. The advantage of the system lies in almost no body roll. Although the new suspension already reduces body roll to a great extent, The ACE still goes one step further. A much softer spring rate can be mounted thus increasing comfort. The ACE compensates for this by exercing it's downward force- on each wheel separately and does hereby not affect the damping force of the shock absorbers. Standard torsion bars can't di this..
The lower signs show the lateral G-force (the force pushing you to the outside of the corner), the vertical is the body roll in degrees. So the ACE allows am unloaden vehicle to drive through a corner at a high speed without body roll and without you having to compensate for this. The 0,4 G-force is enough to push you from the seat, its equivalent to a sharp breaking.
In real life this means that you got a go-cart like steering feel. Unnoticable under everyday driving conditions you will see a tremendous change if you push the car to it's limits. Also through the softer spring rate and the "missing" torsion bars you get much better axle articulation off road.
These here are the electric valves that govern the hydraulic circuitry to the back axle. They are mounted on the outside of the chassis to the left.
Here some diagrams for those technically inclined:
The system is quite complex, adding a tank, lots of lines, a pump, an control bloc and 2 acceleration sensors (one over the front interior light, the other under the body to the right near the A-pillar, don't remove/invert them) to an already complicated car. It's not fed by the PAS pump as system requirements are too much differing. Pressures range from 5 bars to 135 bars max. This pressure can be built up in less than 130/1000's of a second. Flow rate of the pump is between 7 and 9 liters/minute, constant above 1000 rpm. The lines are carefully isolated from the chassis and body as a lot of noise would be generated if they touched somewhere. If you ever have to replace the lines don't wonder if the lines you buy are different. As the factory mounts the lines before the body is assembled, they can use 1-piece lines. Replacement lines are always 2 pieces and you MUST cut the genuine lines to remove them, there's no way to retrieve them in one piece. If removed and remounted later take care not to interchange the lines as this will hurt the system as the actuators on the right and left side take different pressures. If you look at the connections you will notice that they have been clearly marked "A", "B", "P" and "T".
If you break the lines while driving you will not notice anything abnormal. So LR incorporated a red flashing light and a buzzer. If the warning light glows orange, you have a problem and the system has switched to locked actuators, thus acting as heavy sway bars. If the light goes red and the buzzer goes on, you lost so much fluid that the pump can be damaged. Theorhetically the system closes the lines before this and switchs the pump to bypass.In this case you will notice much more body roll but you can still drive.
The oil is the same as the PAS system uses, but both are not connected together. It's an green colored, semy-sythetic oil (Texaco 14315), the tank holds 1,62 liters.
The hydraulic bloc contains an ultra-fine filter. This must be replaced if any dirt comes into the system. In replacing this you must take the greatest care not to contaminate the system. An almost sterile environment and tools are vital. Happy washing- especially if the car has been used offroad.
The electromagnetic valves, as shown on the upper side of this page, are not serviceable. You can only replace the solenoids- that's all. Here you must also work in a "sterile" environment. Even small amounts of dust will ruin your system- according to the factory. Also you must reuse the nuts that hold the electromagnets in place as they are specific part of the magnetic field. Different ones will not work. Every fitting and mounting must be torqued down with an torque wrench to the specified torque. As many garages and most private people don't have this torque wrenches in an open mouth size- better leave this to the dealer.
And here some details about the axle actuators
The actuators are NOT serviceable- again. If they leak you must discard them. Oh, LR, I love you! The connectors of the line to the actuators have special self-centering seal rings. They MUST be replaced and you MUST use the correct part. Or leakage may occur, maybe immediately but more probably after some weeks of use. If air is trapped inside the actuator you must follow the procedure in the manual as there's no easy way to purge it (reminds me of the Series brakes...).