VNT actuator question

[wolfsburgnut]

I finally got my VNT 20 in the mail and I have been working on a microprocessor based solution to control the actuator.  I was wondering do the VNT vanes have binary control (100% open or closed) or is there modulation of the vanes (50% open).

Thanks
Peter

[Turbinepowered]

If I recall correctly, the VNTs are all basically analog controlled. Vane opening/closing is controlled by controlling the vacuum applied to the canister, rather than any kind of electronically actuated control. I don't even think the computer reads the "open" state of the vanes, just infers it indirectly through other sensors relating to the intake air.

[QuickTD]

The VNT vanes are infinitely variable. This is accomplished on the TDI by pulse width modulation of the N75 boost control valve based on feedback from the boost pressure sensor. The valve switches between vacuum and atmospheric pressure. Not sure on the PWM frequency but its slow, probably about 20-30hz? The loop response is a bit soggy on the TDI and leads to some fairly serious overshoot. A direct electric servo would likely work better, but is far outside the budget of auto companies...

[DVST8R]

...A direct electric servo would likely work better, but is far outside the budget of auto companies...

How realistic in cost and application, would this be to add aftermarket? Ie, have the signal intercepted at the N75 valve and directed to a processor of some sort, and then to an electric servo motor and then to the turbo actuator.

[2446]

A direct electric servo would likely work better, but is far outside the budget of auto companies...

That's what they have been switching to in the last couple of years. I think the first ones introduced were on mercedes cars but I bet all of them will be electric actuated before long.
http://www.honeywell.com/sites/ts/tt/PassengerCars_LightTruks3_CP3HXNOKPJPUTB8SLO99Q5SFMZIHC4MW90812155218387_HDKDDYVJ812L6D6X31MZZXXWUYYSW9IFI0812155738248.htm

[Benjamin]

i'm glad to read some about your vnt20 wolfsburgnut  :wink:
i know a guy who got a vnt electronic controlled but i think its not worth it, maybe its just a little bit more efficient.
Vanes controlled by boost was done original/stock on the first Alfa 2.4jtd with vnt turbo, also the croma 2.0tdid use a actuator controlled by pressure.

Greetz, Benjamin

[wolfsburgnut]

My goal is to provide an electronic VNT controller that is easy to set up and really affordable at the same time.  It looks like to me that a lot of people could use this sort of thing and it would make adding a VNT to older engines alot easier.  Thanks for the info so far, if anybody has any more ideas I would love to hear them.

Peter

[wolfsburgnut]

I can see the real challenge here is going to be coming up with a good map.  That will probably just take lots of trial and error.

Peter

[Benjamin]

the guy i was talking about,
a 1.4td with a gt1749v actuator electronic controlled:

http://www.snek-tuning.cz/videa/unod.jpg

Greetz, Benjamin

[fatmobile]

3 inputs:
1. Accelerator position
2. RPM
3. Manifold pressure.

 I've been thinking about connecting the accelerator directly to the turbo can.
 Not with cable but with  a vacuum motor.
 As you step on the fuel you pull a vacuum with the vacuum motor.
 By vacuum motor I mean the dealyos that move the climate control flappers or cruise control.
 More fuel = more air.
 It would really take some experimenting to tune it.
 
 I'm not sure why the RPM would need to be determined.

 The manifold pressure would need to be monitored and controlled so it didn't go too high. There are lots of vacuum solenoids around that could release the vacuum if the boost got too high.... and maybe letting your foot off the accelerator would reset everything by.
 It would be fun to sit in the car, manually moving a lever hooked up to a vacuum motor, that controlled vacuum to the turbo and see what vacuum you need and when.

[jtanguay]

i think named tintin's setup is probably the best mechanical setup ever.  vanes are controlled by the accelerator, but once the desired boost level is met, the wastegate opens the vanes overriding the accelerator cable... ingenius!