Generation 7: Bosch ME9 / ME9.2 Valvetronic Variable Valve Lift Engine Management (N42, N46, N62)

To eliminate the throttling pumping losses inherent in conventional internal combustion engines, BMW developed Valvetronic, first deployed on the 4-cylinder N42/N46 and 8-cylinder N62, managed by the Bosch Motronic ME9.2 (cataloged in the database via 715c4000_r2.a2l, 770115XE.a2l, and BMW ME9.ols):

code

┌──────────────────────────────────────────────────────────────────────────────────────────────────┐  
│                   BOSCH ME9.2 VALVETRONIC VARIABLE VALVE LIFT REGULATION                         │  
├──────────────────────────────────────────────────────────────────────────────────────────────────┤  
│                                                                                                  │  
│   • Core Operating Philosophy: Engine load is controlled ENTIRELY by variable intake valve lift! │  
│   • Variable Lift Authority: 0.18 mm (Minimum Idle Lift) ────► 9.80 mm (Maximum Peak Lift)       │  
│   • Actuator: High-Torque Brushless DC Electric Motor (40A) driving an eccentric worm gear       │  
│   • Valve Transition Time: Full travel (0.18mm to 9.80mm) in under 300 milliseconds              │  
│   • Throttle Plate Status: EDK throttle remains 100% WIDE OPEN during all normal driving modes!  │  
└──────────────────────────────────────────────────────────────────────────────────────────────────┘

11.1 Mechanics of Throttleless Load Modulation

In conventional engines, creating a partial vacuum behind a closed throttle plate consumes significant mechanical pumping work (up to 15% of total engine energy at light cruising loads). Valvetronic eliminates the intake manifold vacuum:

Atmospheric Manifold: The intake manifold stays essentially at ambient atmospheric pressure (pmanifold ≈ 950… 1000 mbar).
Minimum Lift (0.18 mm): At idle, the intake valves barely crack open. Air rushes through the tiny annular slit at ultrasonic velocity, creating intense turbulent micro-vortices that atomize fuel droplets instantaneously without wall wetting.
Maximum Lift (9.80 mm): Under wide-open acceleration, the eccentric shaft rotates to position the intermediate levers for full rocker stroke, achieving unrestricted cylinder charging.

11.2 The Three Distinct Functions of the EDK Throttle Plate

Although Valvetronic modulates engine load, the conventional throttle plate (EDK) is preserved for three auxiliary functions:

Cold-Start Crankcase Scavenging: During the first 60 seconds after cold start, the throttle plate closes slightly to draw approximately 50 mbar (0.75 psi) of intake manifold depression. This depression purges gasoline vapors and blow-by moisture from the crankcase ventilation (CCV) system.
Emergency Fallback (VVT Failsafe): If the eccentric shaft sensor fails or the brushless DC motor jams, the DME triggers an emergency relay that mechanically locks the eccentric shaft at maximum lift (9.80 mm). The DME instantly reverts to traditional throttle-body control, modulating the EDK butterfly valve to maintain vehicle drivability.
Emergency Runaway Brake: In the event of unintended vehicle acceleration, the DME can snap the EDK plate shut to choke engine intake air within 80 ms.

11.3 Eccentric Shaft Calibration & Mechanical Tolerance Adaptations

Due to minuscule manufacturing variations across the intermediate rocker arms, valve lift varies slightly between cylinders at idle (0.18 mm ± 0.02 mm):

Mechanical End-Stop Adaptation: On every ignition key-off, the ME9 DME drives the eccentric shaft motor against its physical minimum and maximum mechanical stops, storing the absolute Hall sensor angles in non-volatile EEPROM.
Smooth Running Control (LLR): The DME continuously analyzes crankshaft angular acceleration after each cylinder fires. If cylinder 3 exhibits slightly lower torque at idle due to mechanical rocker wear, the DME trims individual cylinder ignition advance (KF_ZW_LLR) and injector pulse width (KF_TI_LLR) to ensure a vibration-free idle.