Audi’s reputation is built on its precision technology, such as its electronically controlled engine mount. Technological innovation is hard-wired into the company motto: ‘Vorsprung durch Technik’ (progress through technology).
Perhaps it’s no surprise that the Audi obsession with monitoring, calibrating and optimising every element of a car extends to how the engine connects to the chassis.
After all, an engine mount’s job is not just to keep the engine in place, but to reduce vibration and improve performance. This is where Audi’s electronically controlled engine mount has the edge – it’s not a connection so much as a relationship.
Features of a traditional engine mount
Although chassis and engine blocks are made from metal, connecting these two metal surfaces directly causes unattenuated engine vibration to pass directly to the chassis, body and passengers.
The traditional solution is to use rubber or polyurethane fused with metal connectors for bolting to the chassis and engine block. The elastic material absorbs vibrations, reduces noise inside the vehicle and stops the mounting bolts from working loose.
How an electronically controlled engine mount differs
The Audi electronically controlled engine mount was introduced in 2007 on the A5. Its hydraulic system reduces vibration by adjusting from soft to firm as the motor accelerates and vibrations increase. Electronic engine mounts use numerous means to counter vibrations. Most rely on a structure of vacuum actuators controlled by a computer. The car is then able to dial in the mount’s stiffness based on the current vibration levels, engine RPM, and other strictures. This allows a more comfortable ride in the ‘soft’ position and limits engine movement in the firmer setting.
It works thanks to the dampening liquid in the mount. In fact, hydraulic engine mounts are functionally identical to shock absorbers. Two liquid-filled chambers are divided by a wall with two holes, one small, one large.
Under acceleration, the large hole is shut and the smaller hole restricts liquid flow from one chamber to the other, making the mount stiffer. At low rpm or when the vehicle is idling, the large hole opens. This lets more fluid flow between the chambers, making the mount softer.
In contrast, the passive rubber component of an engine mount applies a constant dampening force no matter how hard the engine is working. This means dampening cannot be optimised to match the shifting output of the engine.
Replacing engine mounts