Engine mounts
 

Hello community,

I finally acquired a D3, 4.2 40V BFM in September last year, but have not been driving with it very much as my daily beater ist a D2 4.2 40V...
After doing some maintainance on it (broken water pump on the oil cooler) I was asking myself why there are no connectors on the "electric" engine mounts. Thus the engine runs smooth as silk, no codes in VCDS...?? :Confused: But a cable attached to the aluminium on the mount, that ends wit a blank connector...
The same thing on the passengers side (LHD) but without any cable even close to the mount...
Picture in attachment...

Probably the solenoid in the engine mounts failed so someone replaced it with a resistor (in the bare plug) instead of replacing the mount.

What about on the passenger side? There is no cable at all :Confused:

Tucked away somewhere?

I will give it a good look as the car is without bumper and the oil cooler/filter right now...

These mounts all failed very quickly (couple of years) and there is/was an Audi TSB to replace them with terminators. What year is the car out of interest, as I'm not sure this was a dealer-fit workaround and/or production change.

The car is a 2004. It seems like it was replaced at Audi, as everything looks so original, the connector with the resistor has an Audi sticker on it :hammer: And an LED lamp inside...
But the engine runs seamles, smooth and no vibrations.
I will replace them anyway but they are so expensive :mad:
We have found the other cable too!

I had an 04 D3 and from memory these hydraulic mounts failed when the car was about 6 years old. (Failed meaning they threw an error code on diagnostics when car was scanned. As they were crazy money and could only be got new at the time, I decided against replacing at the time.
I then kept the car for several more years and never had any issue with vibration or similar. I’d leave them to be honest.

Don't get used ones as they will also be faulty. New ones are probably a waste of money as they will probably only last a couple of years. My first failed at 3.5 years and don't forget these new parts have been sat on a shelf deteriorating for 10+ years.

The FL D2's have similar mounts.
As they're hydraulic, I just thought the electrics were a sensor for when the mount failed?

I didn't think they were or are in any way "active"...

The electrical connection is for a solenoid which controls a valve to an air pocket inside the mount. The ECU controls the effective strength of the mount by switching on / off what is basically an air spring. There's an SSP on them somewhere - I'll see if I can find it.

The D4 actually has a separate computer just to control the active engine mounts http://www.corradov8.com/pics/screwy.gif

Here's Audis take on the D4 4.0T Tfsi Active Engine Mounts :

Active engine mounts: counteracting vibration for greater refinement
Audi normally uses firm, sporty settings for its engine mounts. For many years now certain models – notably the A8 at the top end of the range – and various engines have had switchable electromagnetic mounts. These have two operating settings: at idle speed they have a “soft” characteristic to prevent noise and vibration from reaching the interior, but when the car is being driven a firmer damping rate is selected in order to suppress engine vibration.

The active engine mounting that Audi has developed for the 4.0 TFSI takes this technology a decisive step further – it cancels out engine vibrations with out-of-phase counter-oscillations. The key component is an electromagnetic oscillating-coil actuator. This has a rapid stroke that is transmitted via a flexible diaphragm to the hydraulic fluid in the mounting, which also absorbs oscillating movements from the engine. In the fluid these are overlaid by the actuator movements and cancelled out.

The control units for the active engine mounts receive their signals from two sources. Engine speed is detected by the crankshaft sensor; these signals are used to compute the precise phase and frequency of the actuator signal. Acceleration sensors on the two engine mounts supply the data that determine the amplitude necessary to cancel out the vibration.

When the new 4.0 TFSI is running in the four-cylinder mode, it generates a certain amount of engine vibration and drumming noise of what is known as the second order. They are not typical of a V8, but the counter-vibration generated by the active mounts reduces them to an undetectable level.

At idle speed with all eight cylinders in operation, engine excitation of the fourth order occurs. This too is largely eliminated by the active engine mounts so that the engine appears to be running even more smoothly.

How exacty does this work?? :Confused: