Not sure if this has been brought up. Saw this on the Jan 2002 issue of Automotive Engineering.

Hella electromotive actuators for VNT engines

Hella's electromotive actuator is used in VNT turbocharged gasoline and diesel engines from BMW and Mercedes-Benz, with other turbocharger applications soon to follow.

Hella engineers have developed the first electromotive actuator for turbochargers in cooperation with Honeywell's and BMW. The actuator is used in the BMW 7 Series 3.9-L V8 turbodiesel engine, the BMW Alpina B6, and the Mercedes-Benz S- and M-Class turbodiesel V8, with further turbocharger applications to follow. The turbocharger in these applications has a variable nozzle turbine (VNT) geometry, which helps to produce better torque characteristics at low engine speeds while maintaining power at higher rpm.

The advantages of electromotive (rather than pneumatic) actuators, according to Hella engineers, are quicker reaction time, more accurate position setting, easier turbocharger application in vehicles, better diagnostics capabilities, and the ability to meet stricter pollutant-emissions limits. The use of inductive sensors, complex electronics with microprocessor technology, and better materials for ceramic support has made it possible to create a device with better control accuracy and longer service life under the high-temperature and extreme-vibration conditions near turbochargers.

The electromotive actuator can also be used for other applications in the engine compartment, according to Hella. For example, the concept fulfills vibration and temperature requirements of intake-tract induction-pipe loading flap and EGR valve/flap applications, with either PWM or CAN interfaces.

- Kevin Jost