Cheap and dirty VNT hybrid questions

ketchupshirt88

Veteran Member
Joined
Oct 31, 2012
Location
waupaca, WI
TDI
2005 Passat daily, a bunch of others in the graveyard out back...
so i picked up a used VNT15 to replace the one on my car that has sticky, notchy vane movement.

While cleaning it up i thought to myself that the cold side looks exactly like the GT15 from an AHU. This led me to think "can i strap a 1752 wheel onto it?"

I made a gt15/17 hybrid on the the passat for a whopping $12 in junkyard bits... nothing special but it spooled fine and smoked less on WOT than the stock turbo so i called it an improvement - even if it really wasnt, let me lie to myself in peace...

I assume the larger effective A/R of the VNT's exhaust side will be better at handling the bigger cold side than the tiny GT15 turbine housing did... The GT15/17 seemed to just choke itself out at higher rpm because of this.

So the question is, can the saab's 1752 backplate, comp housing and wheel be bolted on to a VNT1749V? If so, will it provide any improvement over the stock unit?
 

sam-

Veteran Member
Joined
Oct 1, 2008
Location
Belgium
TDI
Golf mk3 tdi AFN
Sorry i can't really help you, even turbine will be pretty small for the 52mm compressor, it will still make improvement over stock vnt17. Since you mixing everything why not trying to find a 1749va or vb turbine ?

When you said you made a hybrid for 12$, does it mean you never balance anything ?
Actually have some turbo at house and won a KTS billet Wheel but i dont know where to send it to balance chra on VSR.
 

ketchupshirt88

Veteran Member
Joined
Oct 31, 2012
Location
waupaca, WI
TDI
2005 Passat daily, a bunch of others in the graveyard out back...
Sorry i can't really help you, even turbine will be pretty small for the 52mm compressor, it will still make improvement over stock vnt17. Since you mixing everything why not trying to find a 1749va or vb turbine ?

When you said you made a hybrid for 12$, does it mean you never balance anything ?
Actually have some turbo at house and won a KTS billet Wheel but i dont know where to send it to balance chra on VSR.
would it need to be machined to fit the VB turbine? looks like it is at least a 1/16th inch bigger.

no i did not balance it, i slapped it together and ran it that way for well over a year. still running, but i retired the car due to rust/body issues.
 

Nevada_TDI

Top Post Dawg
Joined
Aug 17, 2008
Location
Reno, sort of...
TDI
2001 Jetta TDI
Here is some old vnt trivia: the vnt-15 and the vnt-17 both had the same diameter compressor wheels with different turbine wheels. What it sounds as though you have done is re-create a "Stealth 17" turbo. They both had/have the same shaft but the tip height was different allowing the vnt-17 to make more boost at the same effective shaft RPM. The compressor blade/wheel shapes were similar enough you could drop a vnt CHRA into a vnt-15 compressor housing without much trouble. Some of the vnt-17 comp wheel inducers were slightly bigger and a small amount of material would be removed from the inside of the inlet tube to allow there to be no wheel crashing. Some used a simple brake hone to do the job. I have no trouble believing you had a plug and play vnt-15/17 installation, but I am willing to bet if you were to log your intake temperatures before and after you would/should have higher intake air temps now than you did before.
 

[486]

Top Post Dawg
Joined
Mar 1, 2014
Location
MN
TDI
02 golf ALH
I ran a complete saab 1752s rotating assy in a gt1749v turbine housing (stock golf ALH)
just had to do some boring work on the mill (made a form tool to get the radius deeper as well as opening the exducer bore up a bit) and limited the vane travel so they wouldn't 'open' far enough to run into the bigger turbine inducer
still choked up on the turbine before the compressor, just like a stock 1749v. 1752s compressor on 1749v turbine would be worst of all angles, slower spool and same complete lack of power past 3k rpm

get you a td04 from those same junky saabs, it'll be a td04hl-15t-5cm, a pretty good match for a mild build
 

ketchupshirt88

Veteran Member
Joined
Oct 31, 2012
Location
waupaca, WI
TDI
2005 Passat daily, a bunch of others in the graveyard out back...
Nevada - the 15/17 I made was on my ahu, not a VNT on my alh.

486 - I have a td04-15 and after a tuner that didn't want to burn chips told me it wouldn't work well I bought a used he221. My problem there is paying 450 to tune it after I do all the work to make it fit... Just more money than I want to spend now.

Both - I appreciate the input greatly. Thank you.
 

ketchupshirt88

Veteran Member
Joined
Oct 31, 2012
Location
waupaca, WI
TDI
2005 Passat daily, a bunch of others in the graveyard out back...
Nevada - the 15/17 I made was on my ahu, not a VNT on my alh.

486 - I have a td04-15 and after a tuner that didn't want to burn chips told me it wouldn't work well I bought a used he221. My problem there is paying 450 to tune it after I do all the work to make it fit... Just more money than I want to spend now.

Both - I appreciate the input greatly. Thank you.
 

Nevada_TDI

Top Post Dawg
Joined
Aug 17, 2008
Location
Reno, sort of...
TDI
2001 Jetta TDI
[486] I currently am running a 6+6 56mm billet wheel on a GT-15 turbine shaft and wheel and have no problem building boost right above idle and have 24 PSI all the way to red line. I wonder if someone botched the machine work on the 1752 hybrid you mention?
Are we talking about two different things here?
 

[486]

Top Post Dawg
Joined
Mar 1, 2014
Location
MN
TDI
02 golf ALH
Nevada - the 15/17 I made was on my ahu, not a VNT on my alh.
486 - I have a td04-15 and after a tuner that didn't want to burn chips told me it wouldn't work well I bought a used he221. My problem there is paying 450 to tune it after I do all the work to make it fit... Just more money than I want to spend now.
Both - I appreciate the input greatly. Thank you.
You can do the tuning yourself on an ALH, provided it's newer than a 99.5 car you do it through the OBD2 port with a $20 cable.

HE221 is even better, iirc it's a little bigger than td04hl19t in all dimensions
set the wg to 20 psi and it'll burn all the fuel you can get from the stock manual trans fuel system.
[486] I currently am running a 6+6 56mm billet wheel on a GT-15 turbine shaft and wheel and have no problem building boost right above idle and have 24 PSI all the way to red line.
yes, you can make boost right above idle with absolutely anything, but it probably doesn't have the instant response of a horrendously undersized 1749v
also, notice how it falls flat on its face above 3k rpm, and revving past 4k actually loses power? That's the turbine backpressure going absolutely nuts. Mine'd peg a 60 psi gauge on the exhaust manifold (call it 80 psi if it were linear response that far off scale), when only making 25-30 psi in the intake
 

Nevada_TDI

Top Post Dawg
Joined
Aug 17, 2008
Location
Reno, sort of...
TDI
2001 Jetta TDI
[486] My turbo never falls flat on it's face. Never. I also am not using a VNT-20 cold side, I am using a VNT-15 machined cold side, and I also no I do not lose any power all the way to the rev limiter @5500 RPM. Granted, I have never checked the EMP, but it does not act like there is a pressure tug-of-war at any RPM.
 

ketchupshirt88

Veteran Member
Joined
Oct 31, 2012
Location
waupaca, WI
TDI
2005 Passat daily, a bunch of others in the graveyard out back...
You can do the tuning yourself on an ALH, provided it's newer than a 99.5 car you do it through the OBD2 port with a $20 cable.

HE221 is even better, iirc it's a little bigger than td04hl19t in all dimensions
set the wg to 20 psi and it'll burn all the fuel you can get from the stock manual trans fuel system.

yes, you can make boost right above idle with absolutely anything, but it probably doesn't have the instant response of a horrendously undersized 1749v
also, notice how it falls flat on its face above 3k rpm, and revving past 4k actually loses power? That's the turbine backpressure going absolutely nuts. Mine'd peg a 60 psi gauge on the exhaust manifold (call it 80 psi if it were linear response that far off scale), when only making 25-30 psi in the intake

I am not sure im ready to DIY tune my daily driver, especially with winter upon us. I work 45min away so a functional ride is a must... lol.

Im not against the idea but i have got to get to the point of confidence first. Ive tried to read a few threads and alot of it goes over my head... i would be much more confident in going MTDI than tuning an ECU by myself.

Its a 2003, so OBD flashing is available. I already have the 11mm pump on it and it will get the R520's and beefy clutch from red deaths carcass if any sort of upgraded turbo is installed.


i noticed that my gt15/17 on the passat seemed to choke itself out at around 4000rpm but i assumed it was due to the tiny .34? A/R on the hot side and that a VNT with a higher effective A/R when vanes are open would have less issues with that.
 

mk1-83

Veteran Member
Joined
Aug 14, 2010
Location
Holland
TDI
LUPO 1.9 tdi 300+ hp
What go in must go out

So big comp you need the turbine wheel that can handle it.

High emp are mean struggle with hybrid turbo with stock turbine and big comp
Emp go sky high after 4000 rpm and choke engine

So fit large turbine wheel then boost emp ratio not exceed 1:1 1:1.5

What about the td05h 16g 18g 50/68mm comp
with 56/49 12blade ore the quick spool 9 blade turbine wheel on a high mod tdi 12mm .340 big valve ported head 10mm cam all prepared for 350 +
 
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