MBWorld.org Forums - DIY: Lowering an Airmatic W212 with SDS/Xentry

Hey guys,

So I finally got around to connecting my SDS/Xentry setup to my w212.

My car is a 2011 w212 e550 4matic. My Current SDS setup is a C3 Multiplexer, running the 3/2012 version of Xentry on a Dell D830 laptop off the internal hard disk. I actually have the 6/2013, setup for a d630 version as well, but haven't installed it because I haven't had to work on a car new enough where my existing setup hasn't covered it.

So ever since I got the car a couple months ago, I've noticed that the ride height was way high for my tastes, especially for a car with the sport pack and 18" AMG wheels. My 2012 c300w4 sat at least an inch lower from the factory. Since I own an SDS - I figured it was worth seeing if I could lower the car using it. I've done a few other MB's sucessfully.

Here are a couple before pics of my car:

https://cimg0.ibsrv.net/gimg/www.mbw...08e6f5012a.jpg

https://cimg1.ibsrv.net/gimg/www.mbw...3006c9f2dd.jpg

They aren't the greatest but the car had a 1.5-2" wheel gap. Way too high for no apparent reason.

Now you can easily lower a car with SDS but there ARE limits. If you want to "slam" a car or put it in the weeds this is prob not the method you want to use. You are better off with adjustable air ride links to fool the computer into thinking the car is sitting too high. You CAN however lower the car 30-40mm with the SDS.

First thing to do before you get started. Hit the raise button on the airmatic and wait for the car to raise. Then turn off the raise function and let the car settle on its suspension. Wait at least 2-3 minutes.

So with that having been said. Lets get started. I'm willing to do this for other people for a small contribution for my time (beer, lunch, whatever). I do own a shop and I am pretty familiar with these vehicles, plus I'm an electrical engineer by trade who has spent his career in IT. That having been said as long as you are patient, pay attention and follow directions, this is all pretty simple. I'm in central NJ.

First thing's first. You NEED to connect the car to an external charger. You need to maintain a steady source of 12v power to the car while you are connected to the SDS. If the voltage drops too low, you risk damaging the electronics in the car, or possibly rendering a module useless. I prefer doing most of my modifications while the car is off, but the ignition is on. The SAME also goes for the laptop. You do not want the software or the pc shutting down mid session because of the laptop running out of battery. Better safe than sorry.

On the v8 cars, there is a charging post under the hood, I connected our shop's charger to that charging post and set it at 10A charging.

https://cimg2.ibsrv.net/gimg/www.mbw...e81b9ff46b.jpg

Next I booted up the laptop, connected the multiplexer to the obd port and started xentry.

C3 Multiplexer:

https://cimg0.ibsrv.net/gimg/www.mbw...cb7446bf16.jpg

I leave the mutiplexer on the driver's seat an run the cable with the serial port out of the open driver's door window.

I used a stool to support the laptop. Here's what my setup looks like. Car on charger, laptop plugged into AC power, multiplexer connected.

https://cimg5.ibsrv.net/gimg/www.mbw...1c72585905.jpg

Now start Xentry

https://cimg7.ibsrv.net/gimg/www.mbw...08476e15bf.jpg

Let xentry do it's auto tests and determine the vehicle by READING the vin. Don't try to guess, if you guess wrong it will tell you there is a conflict between the vin and the vehicle you chose.

Once the vehicle is detected it will give you a screen full of warnings.

https://cimg4.ibsrv.net/gimg/www.mbw...b202b3ec26.jpg

One thing to note here. On a w212 - command must be ON in order to proceed, so hit the button to turn it on. I initially had it off and then turned it off to comply. Hit the continue button on the bottom right of the screen.

Next select the control unit you wish to work on. Easiest way to do is it to type airmatic into the search screen. On a w212 it will say AIRMATIC (N51/3)

Click on it and let it open the control unit page for the airmatic control module. Then click on the adaptations tab.

https://cimg0.ibsrv.net/gimg/www.mbw...aac1beb25a.jpg

Now hit the plus sign on the left under teach in processes. then click level calibration. Your screen should look as above.

Hit continue on the right, you will get a message that the airmatic unit is already calibrated and do you want to continue and erase the existing calibration.

That will get you to this screen:

https://cimg9.ibsrv.net/gimg/www.mbw...13de1de417.jpg

Your screen will look different, especially at stock height. What you need to do here is use the plus and minus keys to manually set your ride height to your taste. Do not tap the plus and minus keys, stand on them with the mouse and you will see and hear each corner of the car raising / lowering. You need to set this by eye / tape measure to ensure the car sits evenly and to your liking.. The numbers on each level simply represent where the sensor voltage is currently reading, they do NOT indicate a ride height measurement. The only restriction you have is that you have to keep each wheel within the green range. You will notice that changing the front will effect the height of the rear and vice versa. Take your time, and don't be afraid to redo it until it sits the way you want to. I basically set my car at about a 1 1/2 finger gap all around. It took a bit of fiddling to get it right and level. If any sensor goes into the red you HAVE to raise it back into the green level before you can continue. The module will not accept any sensor sitting in the red range, and you will not be able to calibrate the module. The above values are where I stopped and was content with the new ride height of my car. As you can see I still had a bit of lowering left if I wished, but again, my intent was not to slam the car. My car sits a tad bit lower (wheel gap wise) than my w204 c300w4 with the factory sports suspension sits now.

Once you have the levels where you want them, hit continue on the bottom. You will then see a screen asking for the inclination angles for all 4 wheels. This is basically to compensate for the floor's level. MB uses a specific device to measure these angles when the car is on their alignment rack. You can enter any combination of acceptable values (I used -1.3 on all values) assuming the floor was level all around. It was a calculated guess but it seemed to come out fine. The car still has the same basic forward leaning rake as it did but it looks right. Once you enter the inclination angles, select continue to finish and "calibrate" the values. Make sure you get a calibration successful message, otherwise if you get an error, you need to redo it. note: it will save the prior values. If the calibration went ok you will get this screen.

https://cimg2.ibsrv.net/gimg/www.mbw...677cfb8842.jpg

Once you get the level calibration successful message. Disconnect your multiplexer and the battery charger. Then get in the car and start it. Hit the airmatic up button, let the car rise, and then turn off the raise mode, and let the car settle into it's new ride height. Once that is done, take the car for a ride, it will feel a BIT firmer, but nothing crazy. Repeat the raise, wait, lower, wait and the car will settle into it's final ride height.

Now here are some pics of the new ride height, which I think is how the car should have came from MB in the first place:

https://cimg7.ibsrv.net/gimg/www.mbw...b4d08f2be2.jpg

https://cimg9.ibsrv.net/gimg/www.mbw...5c07195a1e.jpg

https://cimg0.ibsrv.net/gimg/www.mbw...7474eb9c4e.jpg

Hope this helps, as I've wasn't able to find the procedure documented anywhere online.

Take care,

George