[PhaseP]

Originally Posted by Phyrexia

Found this while doing some research after lunch. Haven't ever seen it before. I wonder if VT II is less prone to frictional losses than VT I. Seems to be the case. Also some interesting stuff about potential VT III.

http://115.112.66.136/Employee_Infor...MTZ/aug_08.pdf

According to all those documents linked to Version II has indeed has less friction because they are using roller instead of sliding friction between two elements that is part of the Valvetronic.

Version III is not "potential" it is already used in N55 engine.

[PhaseP]

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.

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.

[nsjames]

sounds like they've gone to a sensored brushless motor then.

Generally they use magnets and hall effect sensors, but they may not be precise enough. Might be some sort of encoder wheel and optical things, but that doesn't seem to play well in oil.

I'd be curious to disassemble a gen 3 motor and see what's doing in there.

[Phyrexia]

Originally Posted by PhaseP

According to all those documents linked to Version II has indeed has less friction because they are using roller instead of sliding friction between two elements that is part of the Valvetronic.

Version III is not "potential" it is already used in N55 engine.

Yah I realized this after rereading your post.

[Terraphantm]

Originally Posted by hassmaschine

Yeah, thats pretty much nonsense. Every moving part of valvetronic uses roller bearings. And the S55, an M engine, uses the same system as the N52. We already know the N52 can make good power until at least 7500rpm.

Vtech isnt analogous to valvetronic anyway - its variable timing, which Vanos does better anyway.

Vtec increases lift and duration (the latter which VANOS and valvetronic cannot do), but I believe it accomplishes it by switching to what’s essentially a different cam lobe altogether - so it’s sort of an on/off switch. Eventually they added continuously variable timing like modern VANOS implementations.

[Taskmaster]

Originally Posted by Terraphantm

Vtec increases lift and duration (the latter which VANOS and valvetronic cannot do), but I believe it accomplishes it by switching to what’s essentially a different cam lobe altogether - so it’s sort of an on/off switch. Eventually they added continuously variable timing like modern VANOS implementations.

Absolutely correct. The K series was the first to do this - prior to this, I believe it was fixed cam positions (B series, H series, F series)

[Biginboca]

So I think the next progression would be to see some n55 logs and see how they compare with N52 in the time to open the valvetronic.

That would give some insight I think?

[gT-BMW]

....

[rjahl]

The Turbo "spool" mode may affect how the DME reacts to rapid torque requests. Things get more complicated when the engine has special maps for rapid turbo spool up. Should have special Fuel maps, Vanos maps, fuel maps and such.

I'm still learning how these work.