OCKlasse

Hey guys,

For any of you who knew me before my CL purchase, I had a W202 on hydropneumatic suspension...




My suspension shared many similarities to ABC. Both use hydraulic fluid to adjust vehicle height, and both use nitrogen-filled bladders called accumulators to act as the vehicle's suspension. The primary difference would be that ABC-equipped vehicles use a tandem hydraulic pump, meaning that the pump is constantly running with the motor. My pump was only activated when I wanted to adjust the height.

Here is what I am thinking...

Utilize the factory ABC struts, but remove everything else related to ABC. Convert the power steering pump to a W220 Airmatic-equipped one. Use a non-tandem hydraulic pump with eight valves for height adjustment, two per corner; one valve allows fluid to enter into the strut to raise the vehicle, and the other allows the fluid to leave the strut, thereby lowering the car. Each corner would have its own accumulator, and therefore each corner has its own rebound and dampening. Finally, replace the auxiliary battery with something beefier and voila! All the creature comforts of ABC with a much, much more reliable setup.

The benefits?

• Much more reliable...the pump is only running when you want to adjust the height.
• Height adjustability on the fly (as much as the struts allow)...from very high to very low
• no need to change control arms, struts, add sway bars, etc.
• cost effective

Thoughts? Concerns?

MBtech1098

However the system you describe is not an active system. It sounds like a step backwards. There is a reason the pump is always running, but keep in mind it is not always full volume/pressure as that is regulated as per demand of the system.

With the system you describe, it sounds like you would need sway bars as an ABC equipped vehicle do not have these. Since the system is active it is able to compensate for body roll. In fact when Mercedes first designed the first generation of ABC the system was so good at controlling body roll, they actually had to loosen up the tolerances in the SW because it was too stiff.

OCKlasse

I was waiting for someone to ask this

First thing, I want to run small displacement accumulators. Accumulators fitted with a schraeder valve also can have their pressures adjusted accordingly. The higher the pressure in the accumulator, the stiffer the ride. (in addition, running fluid control valves off the accumulators can limit their dampening abilities even further).

In addition, I plan on driving my car LOW...the lower the vehicle is, the less pressure within the system, therefore less pressure being applied to the accumulators.

If the system had zero accumulators, it would be as stiff as a board, no matter how fast you turned. The balance is how soft do you want the ride in relation to possible body roll. For those that already lower their cars, the rides becomes increasingly stiffer, so it really doesn't matter in my opinion to have accumulators at higher pressure.

The point of this system is reliability...and it would be significantly more reliable. Is it a step backwards in terms of technology? Absolutely. What it does is alleviate headaches for me...and fears

MBtech1098

Do you have a hydraulic, pneumatic, and electrical diagram of this system?

MBtech1098

Also is this a dynamic system? Do you have to initiate change?

Are you aware how the ABC system compensates for body roll, it does not keep the system at a higher pressure at all times.

OCKlasse

I'm going off my previous hydraulic knowledge and it always worked well for me. No pneumatic except for the nitrogen-filled accumulators.

I can show you a plumbing diagram if you really want it...I could draw it up. Basically four check valves, eight valves, four fluid control valves, and four accumulators (with fluid control valves as well).

As I said before, this is not meant to compensate for sway. The additional stiffness will do that. It's meant to allow for height adjustment like a lowering module allows, with the added benefit of a much more simplified setup.

MBtech1098

I got you...not a dynamic system. I'm sure it will work fine for what you want. Me personnally I would stick with ABC, I prefer performance over style.

saintz

Why would this be more reliable? The issues with ABC are not the pump running all the time. It's wear and fatigue at seals, hoses, valves, etc. It sounds like you would still have all these issues.

fatmike

Ive been waiting for you to do this lol. then you said you might not!

What do you plan to do about error codes?

OCKlasse

Except you have these issues because there is so much pressure in the lines all the time from the pump. Not to mention the valve bodies are constantly opening and closing allowing fluid to enter and exit. This is a static system and is only operated when lifting and lowering the car. The pump is now working 1% of time it once was and the valves are maybe working 5% of what they once were. Couple that with industrial hydraulic hosing. A much better alternative, IMO.

OCKlasse

Sup Mike? ABC can be coded out of STAR. Yippee!

MBtech1098

The actual issue with ABC as any hydraulic system is not system pressure, but system contamination. The orfices in the valveblocks are quite small, all it takes is a slight bit of contamination to hang valve.

saintz

I think I understand now when you say it's a static system. You're still going to have issues with the struts and hoses (at least half the hoses) as these are still going to be pressurized just like they are now. The benefit would then be the valve block and pump are basically no longer used.

The downside is the car basically no longer has a suspension. It doesn't modify pressure to account for cornering, road irregularities, vehicle dynamics, etc. The reason you don't need sway bars is because the system actively corrects for sway. With this you're basically running a shock with no spring or sway bar. On a car that weighs this much, I predict very bad things in terms of handling.

radride

Agreed.

R.K.

OCKlasse

LOL you guys think I have no experience with this stuff. Fair enough, I will just have to prove you wrong. If you read my other posts, you see where I talk about all of your points.

I like challenges

The thing is you guys know hydraulics in terms of this car, and not in terms of applications outside of this car.

MBtech1098

I used to work on construction equipment...I am very familiar with hydraulics. But as mentioned your system will not compensate as per the other members mentions. Like I said, it will probably work great for what you want.

saintz

Have you done hydraulics on another car without sway bars?

saintz

Also, there's the issue of squat and dive at acceleration and braking. To correct that, as well as to correct cornering (without sway bars), you are going to need to run bone jarring pressures to match ABC performance.

OCKlasse

A hydraulic setup without accumulators would have zero suspension. The car would have zero sway regardless if it had sway bars or not. A low ride height works three fold: it reduces the car's center of gravity it reduces the travel of the strut, and it reduces the pressure within the system. These three items coupled with small accumulators set at high pressure (say, 500 psi), will make the car stiff. Will it sway, I'm sure as much as a coilover conversion would or less.

The point is not to recreate ABC. The point is a more reliable, affordable option to ABC, and a cheaper alternative to a coil conversion, while still keeping the height adjustment capabilities. I love ABC, but I don't like living in fear, either. My car has paperwork with $7,000 worth of ABC repairs, and I would rather not live that myself.

1995E320Cab

Do you have an estimate of what the set up you want to do would cost VS a coilover conversion on your car ?

.

OCKlasse

Around $2000-2500 with a new power steering pump I believe. Not too far off.

1995E320Cab

That's parts only right ?

So what would the parts only price be for a coilover conversion ?

.

OCKlasse

I would imagine close to $3000-4,000. Including new struts, shocks, springs, control arms, sway bars, power steering pump, etc.

I'm thinking I can do it all for very close to $2,000 using nice stuff. A big money saver would be labor...not having to remove any of the factory ABC struts.

BRABUSCL600

http://youtu.be/uPPdOD9jXu8

nola_penguin

I know alot about this stuff. Unless you have some insane lbs pushing on it you're going to throw your camber off badly when hitting any bump without all wheels. It's great in theory but will be a ****ty ride and cause a lot of havoc on other suspension components.