Garrett GT2056 turbo

[vanagonturbo]

Conclusive result on the gt2056. Not a good turbo for my application. Spools quite fast (faster than a t3), but hits surge at about 3800rpm and 16lbs of boost.

For clarity as to what I put it on, its a 2nd overbore 1.6l hydraulic TD block, ceramic coated crowns, moly coated skirts, 3" dp to a 2.5" straightpipe exh, cranked up pump, 1.9l head ported, ALH intake manifold, large front mount IC, 2" hotside charge pipe, 2.5" coldside charge pipe,a bunch of other stuff.... in a scirocco.

So that is what I have and this turbo does NOT work well with my application.

[Alcaid]

What's the part number of that turbo? Funny surging on that low boost and that high RPMs.... 

[RabbitJockey]

yeah i agree that doesn't seem right especially with that setup

[R.O.R-2.0]

its just a straight 2056 right? or is it a VNT? if so, do you have vane control?

[vanagonturbo]

No V. Its a straight wastegated turbo. PN# GT2056 - 751578 - 2

[410]

I ran into a similar issue with what I thought was the turbo surging at higher rpms and it turned out that I was starving for fuel at the injection pump.  I changed the fuel filter and installed a bigger feed pump and problem solved.

[vanagonturbo]

the surging is clearly audible. It is a loud fluttering noise. I dont think fueling is a problem because when I set the charge pressure to 15psi, I can easily hit 1500°F on the freeway..

[410]

the surging is clearly audible. It is a loud fluttering noise. I dont think fueling is a problem because when I set the charge pressure to 15psi, I can easily hit 1500°F on the freeway..

Man that's strange but I don't doubt you at all.  I had read a post somewhere on tdi club that turbo surge is impossible after 2000 rpm.  I'm sure they were talking about vnts but the same rules should apply to all turbos.  That's what led me to find my fueling issue.  My fuel issue also felt and sounded like a fluttering of some kind but I think that was caused by the style of lift pump I had.  
I wonder what would happen if you increased the size of the hot charge pipe to 2.5" as well.  What kind of air filter do you have on it?

[vanagonturbo]

The air cleaner is of the K&N variety. Its kinda ovalish. I have not done a pleat count though. I also find it rather wierd that it would surge that badly at such a low boost pressure, but the only logic I can deduce from it is that the engine does not process enough air and that is what is causing the surging.

changing the hotside charge pipe might make a difference, but I doubt it. After all, when it leaves the intercooler and goes to the intake manifold, it is reduced to 2" as it is an ALH manifold.

Like I said, perhaps I am doing it wrong..

The fluttering is very prominent after 16psi and it holds there. One thought is that when the engine is not up to operating temp, it pulled to 23psi without surging, but after it got hotter, it would flutter. I kinda stopped messing with it cause I didnt want the shaft to break.

FWIW, it was mentioned a while ago in another thread that I posted in that surge does not happen with stock engine that has been modded. I tend to disagree. On the engine that was in the Scirocco before (1.6l NA 11mm bolts, metal HG, mech lifters, blocked off DV, disconnected WG) I noticed that after a WOT pull, the turbo would surge during spool down making a fluttering noise. Someone said that it was not possible as the turbo would stop spooling faster than the engine could decel. After that I went out and drove the car and observed boost still present during decel, so I debunked that suggested idea..

Same noise, just much louder in this application..

[Alcaid]

Conclusive result on the gt2056. Not a good turbo for my application. Spools quite fast (faster than a t3), but hits surge at about 3800rpm and 16lbs of boost.

For clarity as to what I put it on, its a 2nd overbore 1.6l hydraulic TD block, ceramic coated crowns, moly coated skirts, 3" dp to a 2.5" straightpipe exh, cranked up pump, 1.9l head ported, ALH intake manifold, large front mount IC, 2" hotside charge pipe, 2.5" coldside charge pipe,a bunch of other stuff.... in a scirocco.

So that is what I have and this turbo does NOT work well with my application.

First of all, thanks for sharing your results, posts like this gives so much value!

Secondly, I've double checked the compressor map of your turbo (http://turbobygarrett.com/turbobygarrett/catelog/Turbochargers/GT20/GT2056_751578_2.htm) and compared it to how it performed:

For it to hit surge at around 38000rpm would predict a volumetric efficiency of 65-70%, I thought (and hoped) a ported AAZ head would perform better but your results show us otherwise.

A VNT turbo would give you the added benefit of controlling spool and therefore being able to avvoid surge when a (too) big turbo is used, but that is IF you are able to controll the VNT mechanism properly...

[vanagonturbo]

hey, its best to offer what you have observed than not say anything at all right?

One thing to note that I saw I didnt mention, the cam has been swapped with an ALH unit. After finding the problem in my other thread, I wonder if its possible that I have changed so many things that I might be missing something. The ALH cam is very evident with its lack of overlap. It is visible to the eye by comparison with the AAZ cam... perhaps that is something that contributes? If anyone else thinks this might be a source of the surging, I have no problem swapping the cams out.. Just trying to avoid another turbo purchase

[Alcaid]

The cam would indeed affect the volumetric efficiency, how much an to what degree, I don't know, give it a shot 

[410]

I'm hoping you give the cam swap a try.  You've peeked my interest as well!

[vanagonturbo]

Changed the cam. Surging is gone. Turbo is still a little laggy so I am going to mess with the pump a bit and see what I can come up with. 25psi @5700rpm

[Alcaid]

That's great news How much is your governor modded?