Anti-Jerk Damping
Single-mass flywheel resonance and the ARMIN / KFFDLGO damping recalibration.
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A frequent mechanical modification on performance Volkswagen Golf GTI and Jetta 1.8T vehicles is replacing the heavy factory Dual-Mass Flywheel (DMF, weighing 26.5 lbs / 12.0 kg) with a lightweight Single-Mass Flywheel (SMF) manufactured from forged chromoly steel (14 lbs) or billet aluminum (9 lbs). While an SMF drastically reduces rotational inertia—allowing the engine to rev and drop RPM much faster—it completely eliminates the internal mechanical damping springs that isolate torsional firing pulses from the transmission.
On factory calibrations, an SMF swap causes violent low-RPM driveline bucking (the "kangaroo effect") during throttle tip-in and parking lot cruising, alongside harsh transmission gear rattle. In Bosch Motronic ME7.5, this instability is actively governed and eliminated by the ARMIN (Antiruckeln / Anti-Jerk) closed-loop control system.
┌──────────────────────────────────────────────────────────────────────────────────────────────────┐
│ BOSCH ME7.5 ARMIN (ANTI-JERK) DAMPING REGULATOR ARCHITECTURE │
├──────────────────────────────────────────────────────────────────────────────────────────────────┤
│ [ Crankshaft VR Sensor (G28) ] │
│ │ │
│ ▼ │
│ High-Resolution Angular Acceleration (d_omega/dt) │
│ Measures 60-2 trigger tooth timing variations │
│ │ │
│ ▼ │
│ [ Driveline Resonance Detection Filter ] │
│ Compares acceleration spikes against ELAUF threshold │
│ │ │
│ ▼ Torsional Oscillation Detected! │
│ ┌────────────────────────────────────────┴────────────────────────────────────────┐ │
│ ▼ ▼ │
│ [ Fast Path: Ignition Angle Retard ] [ Slow Path: Electronic Throttle]
│ Solenoid / Combustion Spark Intervention Dampens rate of throttle plate│
│ Delta_ZW = f(KFFDLGO, d_omega/dt) plate opening (DVE) │
│ Instantly drops peak cylinder pressure by up to -8.0° KW Smooths intake airflow surge │
└──────────────────────────────────────────────────────────────────────────────────────────────────┘32.1. The Physics of Driveline Resonance with Single-Mass Flywheels
The automotive powertrain behaves as a torsional mass-spring-damper system:
- Mass 1: The engine rotating assembly (crankshaft, connecting rods, pistons).
- Spring / Damper: The clutch disc damper springs and transmission input shaft elasticity.
- Mass 2: The vehicle chassis inertia reflected through the final drive differential.
When the heavy dual-mass flywheel is removed, the system's natural resonant frequency (fn) shifts from a heavily damped 7… 9 Hz up to an undamped 13… 16 Hz. At low speeds (1200 to 2200 rpm in 1st or 2nd gear), applying light throttle triggers an undamped torsional resonance: the vehicle bucks forward and backward violently as the driveline winds and unwinds.
32.2. The Key Calibration Parameters (06A906032LP)
KFFDLGO(Anti-Jerk Damping Factor Map):- Scalar that scales the derivative of engine speed change (d2ωdt2).
ELAUF(Anti-Jerk Speed Threshold):FDLD(Differential Damping Derivative Gain):
32.3. Calibration Protocol for 14 lb & 9 lb Single-Mass Flywheels
When converting to a lightweight flywheel, leaving factory KFFDLGO untouched causes the ECU to under-damp the higher resonant frequency, resulting in chronic bucking.
Step-by-Step Recalibration Instructions
- Increase
KFFDLGODamping Factor in 1st and 2nd Gear:- Because a lightweight flywheel has less rotational momentum to smooth four-cylinder idle pulses, transmission gear rollover rattle (idle chatter) is common in neutral with the clutch released.
- Using VCDS Channel 01 (or editing EEPROM byte
0x00C2), raise baseline idle from 800 rpm to 880… 900 rpm. The higher crankshaft velocity completely silences transmission gear chatter.
- Smooth Overrun Transition (
KFFWL/DMLLR): - Raise Hot Idle RPM via VCDS (Channel 01):