Working Principle and Components of the Porsche PADM System
Overview:
The PADM (Porsche Active Drivetrain Mounts) system is designed to dynamically adjust the stiffness of the engine mount connection using magnetorheological damping technology. In Sport or dynamic driving modes, the system increases the stiffness of the engine mounts to provide greater engine support during cornering. By maximizing the rigidity of the connection, it helps reduce vehicle center-of-gravity shift, effectively creating a rigid link between the engine and the chassis. This enhances steering precision and vehicle responsiveness.
In Normal or Comfort modes, the system softens the connection between the engine and the chassis, reducing the transmission of engine vibrations to the cabin and improving overall ride comfort.
Working Principle:
The PADM system uses electronically controlled mounts filled with magnetorheological . These mounts can change their damping characteristics in real time based on driving conditions. The system adjusts the stiffness of the drivetrain mounts through the following process:
Sensor Input: Various sensors (such as acceleration sensors, yaw rate sensors, engine torque sensors, etc.) monitor vehicle dynamics in real-time.
ECU Analysis: The control unit (ECU) processes the sensor data and determines the optimal damping force required.
Actuator Adjustment: Based on the ECU commands, actuators within the mounts adjust the internal fluid behavior (viscosity or pressure), changing the mount stiffness.
Dynamic Control: During aggressive driving or cornering, the mounts become stiffer to reduce drivetrain movement, improving handling and response. Under normal driving, the mounts are softer, improving ride comfort and reducing vibrations.
System Components:
Active Engine Mounts: Magnetorheologically controlled mounts located at the engine and transmission, capable of adjusting stiffness dynamically.
PADM Control Unit (ECU): An electronic control unit responsible for processing sensor inputs and controlling the mounts.
Sensors:
- Engine torque sensor
- Acceleration sensor
- Yaw rate sensor
- Vehicle speed sensor
- Gearbox status sensors
CAN Bus Communication: The PADM system communicates with other vehicle control systems via the CAN bus for real-time data exchange.
Diagnostic Integration:
PADM is integrated into the vehicle’s onboard diagnostics (OBD) system. Fault codes such as 001013 and 001023 typically indicate sensor failures related to the PADM system. These faults often result in the system reverting to a default (passive) mount setting, reducing its performance benefits.
Why Is the Failure Rate of OEM Sensors So High?
After disassembling and analyzing numerous sensors, we discovered a common issue across all of them — sensor detachment. This is most likely due to improper securing methods, as the sensor components are glued in place rather than mechanically fixed. Additionally, the engine mounting location subjects the sensors to frequent vibrations. During aggressive driving maneuvers, the pressure of the magnetorheological fluid can spike suddenly, which may cause the measurement chip to come loose.
Sensor Calibration
OEM sensors are calibrated using data collected via the OBD system. By analyzing large sample sets under standard atmospheric pressure, it was found that when the vehicle is stationary or idling, most sensors read between -100 kPa and 0 kPa. Notably, this range varies from vehicle to vehicle, and even between left and right sensors on the same vehicle.
Theoretically, the reading at rest should be 0 kPa or slightly positive, and should not show a vacuum (negative pressure). However, a deviation within 100 kPa does not affect the actual function of the magnetorheological system, as it relies on relative signal changes, not absolute values.
This discrepancy may reflect a specific calibration strategy by Porsche.
Ultimately, we chose to retain the original characteristics of the OEM sensor’s data. It is important to emphasize that this is not a design flaw, but rather an intentional implementation. We believe that replicating the OEM sensor's behavior is the most reliable solution.
Sensor Improvements
To address the issues observed in OEM sensors, we made structural improvements while maintaining the same working principle — a Wheatstone bridge circuit, with signal amplification and filtering before output.
The key enhancement is in the installation and packaging of the sensing chip. We reversed the chip’s orientation and adopted a fully encapsulated design, with the chip securely soldered to the PCB via pins. This improves resistance to both vibration and cleaning damage. The outer housing is made of a single-piece aluminum enclosure, which is both durable and visually refined.
Due to the OEM connector integrating both coil and sensor wires into a single unit (as is the case on 991 and 981 models — though 982 models allow separation), we retained the two coil wires in the OEM connector. The remaining three sensor wires are separated and routed independently to facilitate easier installation.
