How do active motor mounts work?
Active motor mounts use sensors, a controller, and an actuator to apply counteracting forces that cancel engine vibrations, delivering smoother operation and reduced noise and harshness.
What they are and why they matter
Traditional engine mounts are passive devices that damp vibrations through rubber and hydraulic elements. Active motor mounts go further by continuously monitoring engine motion and adjusting stiffness and damping in real time to suppress unwanted movement across a wide range of speeds and loads. The result is a quieter cabin and a more refined driving experience, especially on turbocharged or high-torque setups.
Key elements of the system
These components form an active control loop that translates raw engine movement into precise counterforces.
- Sensors (accelerometers, crankshaft position sensors, and sometimes engine torque sensors) that detect vibration and movement
- Control unit (ECU/VCU) that runs software to compute the required counterforce
- Actuator (electromagnetic, electrohydraulic, or magnetorheological) that generates the opposing force
- Mount housing with a hydraulic or MR fluid path that transmits the actuator's force to the engine
- Power supply and electronics for fast response and fail-safes
These components form the backbone of the active control loop and enable real-time adjustments to engine mount stiffness and damping.
Actuation technologies used in active mounts
Designs vary by how the mount generates the counteracting force. The main approaches include:
- Electromagnetic actuators that push or pull on a movable element within the mount to cancel engine motion
- Electrohydraulic systems that variably pressurize fluid in the mount, changing stiffness and damping
- Magnetorheological (MR) fluid-based mounts that alter fluid viscosity with a magnetic field to adjust damping characteristics
In practice, many systems combine multiple techniques or switch between modes to balance responsiveness, durability, and cost.
How the control loop operates in real time
When the engine runs, vibrations and torques vary with rpm, gear engagement, load, and road input. The control unit continuously processes sensor data and computes the optimal counterforce and stiffness profile. The actuator then applies this force to the engine block or mounting structure, reducing transmitted vibration to the cabin. The system must react within milliseconds to be effective, and it often includes safeguards to revert to passive damping if a fault is detected.
Sensor inputs and decision logic
Common inputs include engine RPM, throttle position, torque estimates, acceleration data, and vehicle speed. The software uses a model of the drivetrain dynamics and fabricates a counter-signal that destructively interferes with the engine vibration, effectively softening fluctuations that the driver can feel as shudder or noise.
Practical considerations and limitations
Active mounts are more complex and expensive than passive ones. They require robust electronics, power management, and diagnostic capabilities. Potential drawbacks include higher maintenance costs, possible reliability concerns in harsh conditions, and the need for careful calibration to avoid introducing new noises or resonances at certain speeds.
Real-world use and driving experience
Automakers deploy active motor mounts primarily on performance-oriented or luxury models and some high-end mainstream vehicles as optional or standard equipment. They are designed to improve idle quality, reduce drivetrain shudder under torque reversal, and smooth transitions during shifts or abrupt throttle changes. For drivers, this often translates into a quieter cabin and more refined feel, especially in turbocharged engines that generate strong vibration at low RPMs.
The level of refinement varies by implementation and tuning. When the system is working well, the difference is subtle but noticeable—engine vibration fades into the background, letting other sounds define the driving experience.
Summary
Active motor mounts blend sensing, intelligent control, and real-time actuation to counter engine vibrations and damping. By adjusting stiffness and applying targeted forces, these systems reduce noise, vibration, and harshness inside the vehicle while balancing weight, power consumption, and cost. Ongoing advances aim to broaden adoption, improve reliability, and refine ride quality across more vehicle segments.
