Thread: VNT turbo control

Steve,
I have a GT2556v on my 300 Tdi. I'm not sure if it's any help, but you are welcome to check it out if you need to.

Cheers, Murray

Thanks Murray.
Don't suppose you've got the P/N of that actuator do you? Might be a good place to start.

Steve

Some options.

1. The two bolts that hold that vacuum actuator on will let you bolt up a wastegate actuator to the same bracket.

2. Conjure up your own vacuum/boost control.

I came up with a vacuum/boost control scheme a while ago, but I'm not sure where I posted it. Basically using a vacuum line, a boost line, a restrictor and an adjustable tap to set your boost level. The plan is that with no boost the vacuum cranks the vanes around to provide early spool and as boost comes up it reduces the vacuum to modulate the boost to your set level.
All adjusted through one little tap.

But I haven't tested the system yet.

So that design uses the vacuum actuator or pressure one (I'm guessing vacuum)?

If I understand correctly - basically what you're describing is the actuator line between two restrictors - one of which is variable to allow initial adjustment.

Should be easy enough to model up on the bench for a start to get it roughly working.

Steve

Originally Posted by steveG

So that design uses the vacuum actuator or pressure one (I'm guessing vacuum)?

If I understand correctly - basically what you're describing is the actuator line between two restrictors - one of which is variable to allow initial adjustment.

Should be easy enough to model up on the bench for a start to get it roughly working.

Steve

You've got it. Let me know how it goes.

Will do.
Again, just to confirm my understanding:
- Engine off - spring in vacuum actuator holds vanes fully open
- idle - no boost - vacuum holds actuator against minimum nozzle stop
- as boost builds it counteracts the vacuum and allows the actuator to move vanes toward fully open

- If you end up with vanes fully open its like having a non-wastegated turbo - so if you have too much boost at that point it means too much fuel?

Do you have any info about the relationship of boost/rpm/vane opening?
Just trying to get a feel for whether the vanes should stay closed from idle until maximum boost - then open to maintain boost, or whether they should start to open gradually as soon as boost starts to build to delay maximum boost until higher rpm.

Steve

Originally Posted by steveG

Will do.
Again, just to confirm my understanding:
- Engine off - spring in vacuum actuator holds vanes fully open
- idle - no boost - vacuum holds actuator against minimum nozzle stop
- as boost builds it counteracts the vacuum and allows the actuator to move vanes toward fully open

- If you end up with vanes fully open its like having a non-wastegated turbo - so if you have too much boost at that point it means too much fuel?

Do you have any info about the relationship of boost/rpm/vane opening?
Just trying to get a feel for whether the vanes should stay closed from idle until maximum boost - then open to maintain boost, or whether they should start to open gradually as soon as boost starts to build to delay maximum boost until higher rpm.

Steve

Yes, that's the operation I was going for. This means your vanes cycle from open to closed with every engine start/stop which I think has to be good for keeping them free and moving.

If you can get this one working right it should proportionally open the vanes as boost arrives. But we won't know until you've tried it.
The cost should be pretty low so if it doesn't work and you need a pressure actuator anyway you won't have lost much.

Just picked up a couple of small adjustable restrictor valves so will try and get something mocked up over the holidays.

Any idea what sort of vacuum the pump pulls? I can't seem to find the figure in the manual I have here.

Steve