Quote:
Originally Posted by nsjames
that's mostly dependent on the stepper driver. There are certainly NEMA motors capable of 3K RPM with the appropriate driver. I'd imagine that the VT motor is a custom bit, and with a custom driver, so it can really be anything that BMW wanted. I'd say it's not out of the realm of possibility that it's a 2-3K RPM motor. The biggest problem of driving steppers quickly is a lack of torque. I'm not sure what the requirements are to move the valvetronic mechanism.
A sensored brushless motor will be superior in torque and speed, but probably not be as accurate. I imagine that it's not such a big deal because you still have an external sensor to tell you shaft position, and you're not relying entirely on the accuracy of the motor.
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Thanks for your input on the stepper motors.
The version 3 of Valvetronic which N55 uses, has done away with the eccentric shaft sensor. The sensor is integrated with the motor, or it is just the sensor of the motor itself. It is bathed in oil, inside the engine.