semi-active suspension vs active suspension
 

Looking at the E500 booklet it keeps stating semi-active suspension and the SL states fully active suspension?

What is the difference? Is it that on the SL you can dial it up to any setting between 1-10 and on the E it is Comfort, Sports 1, Sports 2?

Thanks guys..

Simple. The SL and S or CL using full active airmatic, which the airmatic is only "one" unit. The E is semi. The airmatic and shock absorber is separate unit.

So, do we have a traditional shock absorber in our car? What is the advantage to active vs. semi suspension.

Thanks..

The CL uses ABC, not airmatic. ABC uses high pressure hydraulics to modulate the suspension vs airmatic which uses air at a much lower pressure.


ABC, an active suspension system, utilizes a coil spring and an electronically controlled hydraulic cylinder in series, plus a separate gas-pressurized shock absorber at each wheel. Using a total system pressure of up to 2,900 psi, ABC continually adjusts each wheel's suspension to counteract vibration, pitch, dive, squat and roll. ABC also provides automatic 4-wheel level control, driver-selectable ride height and automatic lowering at higher speeds2. Driver-selectable sport mode virtually eliminates body roll for even flatter cornering and sharper handling response.



Airmatic Dual Control air suspension with Adaptive Damping System (ADS II) Standard, semi-active suspension that provides greater ride comfort yet responds to reduce pitch, dive and roll during braking, accelerating and cornering by instantaneously firming up spring rates as driving dynamics change. Electronically controlled pneumatic spring-struts integrate variable-rate shock absorbers and coil springs. ADS II continually optimizes ride and handling by automatically selecting one of four damping profiles for each spring-strut every time a wheel changes its direction of up-down travel. Dual driver-selectable sport modes engage firmer damping profiles either full-time or at lower thresholds of body movement. Automatic 4-wheel level control includes driver-selectable ride-height control, and automatic speed-sensitive lowering at higher speeds or with sport mode selection.

Active suspension replace springs with hydraulic cylinders that respond to inputs at a frequencey greater than 10 cycles/sec. I thought the ABC system on MB was close to 100 cycles/sec, how ever I may be wrong.

Semi-active is what ever you want it to be. Many cars have dynamically adjusting shock stiffness. The coolest implementations are on new GM vehicles where the viscocity of the fluid is changed magnetically!

BMW has dynamically adjusting anti-roll bar rates and electronically adjustable shocks.

I believe MB has dynamically adjusting supplemental air springs and dynamically adjusting shocks. This is a more common implementation where the ride height and spring rate can be adjusted. Usually, the response rate is too slow to really be dynamic, however I am not sure about Benz.

More info:

The CL is fitted with Active Body Control (ABC) as standard equipment. As in the case of air suspension, hydraulic Active Body Control (ABC) is a fully supporting suspension system with a vehicle level independent of load. The advantages are a high level of suspension/ride comfort, low level of pitching motion when starting off and braking. Rolling motions due to alternating body movement (excitation) are reduced significantly even without a torsion bar at the front and rear axle.

Mercedes-Benz – the company that was a pioneer in ABS anti-lock brakes, traction control, and ESP stability control – is launching the world’s only active suspension system. After 20 years of research and development with several types of prototype systems, Mercedes-Benz is launching its ABC (for Active Body Control) active suspension with the debut of the 2000 CL coupe, the new top-of-the-line Mercedes model. ABC active suspension virtually eliminates body roll in cornering, accelerating and braking.

While active suspension has the potential to actually lean a car into every turn (like a bicycle or motorcycle), Mercedes-Benz engineers use its interplay of hydraulic, electronic and mechanical parts to reduce body roll by 68 percent, still providing the driver with helpful feedback through the vehicle chassis. A comfort/sport switch on the dash can make it 95 percent reduced roll if the driver prefers sportier handling.

Active suspension provides the most effective balance to date between ride comfort, handling precision and driving safety. The flagship CL coupe has the sumptuous ride comfort of an S-Class sedan, which comes with Airmatic air suspension, while the coupe’s crisp handling surpasses most high-performance sports cars.

Four Lightening-Quick Hydraulic Servos Are The Key
Two Computers, Four Control Valves, and 13 Valves Make it All Work
A total of 13 sensors monitor body movement and vehicle level so that the ABC computer is supplied with new data every 10 milliseconds. This sophisticated system senses body movement just as it begins, and makes corrections via the servos within a fraction of a second.

Two sensors at each end of the car measure vehicle level, while nine sensors – in the front end, under the front passenger seat and in the center console – detect vertical and transverse body movement. Data from the sensors is used by two microprocessors that compute signals for operating hydraulic valves that control each of the four hydraulic servos on the springs.

ABC active suspension system uses four hydraulic servos, one on top of each steel coil spring. Located between the body and the springs, these pistons apply additional forces in response to split-second signals from the ABC computers. As a result, the servos actually regulate the action of the springs in relation to incipient body movement.


Two Computers, Four Control Valves, and 13 Valves Make it All Work
A total of 13 sensors monitor body movement and vehicle level so that the ABC computer is supplied with new data every 10 milliseconds. This sophisticated system senses body movement just as it begins, and makes corrections via the servos within a fraction of a second.

Two sensors at each end of the car measure vehicle level, while nine sensors – in the front end, under the front passenger seat and in the center console – detect vertical and transverse body movement. Data from the sensors is used by two microprocessors that compute signals for operating hydraulic valves that control each of the four hydraulic servos on the springs.

High Hydraulic Pressure Also a Key To Fast Response
A special engine-driven oil pump generates 2840 pounds per square inch of oil pressure, which helps ensure that the four servos operate within a few milliseconds. The system checks and re-checks itself every 10 milliseconds! An accumulator or pressure reservoir at each end of the car keeps pressurized oil ready, so that the energy for split-second damping and springing is always available, and an oil cooler maintains the right operating temperature in the hydraulic system.

Stabilizer Bars No Longer Needed
The ABC active suspension handles relatively low frequency body movements of five Hertz or less, which means that stabilizer bars are no longer necessary. However, higher frequency vibration is still absorbed by conventional gas-pressurized shock absorbers and steel coil springs. Although Mercedes engineers tested a version of the system that operated over the full frequency range of 0-30 Hertz, they found that its energy requirements adversely affected performance and fuel economy noticeably without significant gains.

I believe it was blueSL who actually saw a R230's ABC sensors being tricked and he described it something along the lines of the SL going crazy like a horse!

You the man awiner........
Thanks for that info, very enlightening....

GOD bless , you must be the MB godzilla :).
let me have that old mercedes you dont use anymore, and let me experiment on it to get to your level .
mercedes benz should pay you, hands down. thats some brain servos that are very valuable to the benzworld.
im just a fan that collect them off auction sites just to clock in on time. hahahahahaha

I dunno, I time to time have music slightly on when I am hammering the car in sports+ and I see no difference whatsoever.