View Full Version : VNT Turbo
Jimmy_GTT
12-09-2010, 08:19
I'm playing with the idea to go for a VNT.
What kind of VNT shall I search for? I know it is also Garrett, but from what car? What modifications are necessary to get it fitted to a GTT?
If someone has a good working unit for sale please let me know. ;)
Currently I have a T2/T25 hybrid and I'd like to upgrade. And as I've read most of you are prefering VNT than T25. I'll also install EFI during the winter.
I'm open for all good advises. Thanks!
The gt2052v off an Audi 2.7 v6 tdi will mate to the gtt manifold. With ref to mods you will need to rotate housings not as easy as it sounds on the vnt as the rear housing has the vane system within so that will need adjusting, Boosted operated actuator, then oil drain adaptor, oil feed adaptor, custom turbo elbow, also the compressor housing outlet will need modification as it faces the wrong way so will need cut and weld. Then once that all done you will need to then start setting the vnt up to how you want it to boost on your car.
This is an Audi vnt I done a while back partly nodded just needs the compressor housing outlet done and needs a boost operated actuator fitted.
http://emob252.photobucket.com/albums/hh25/GTTJames/VNT/IMG_5245.jpg
http://emob252.photobucket.com/albums/hh25/GTTJames/VNT/IMG_5246.jpg
The next pic you should be able to make out the part number of the vnt
http://emob252.photobucket.com/albums/hh25/GTTJames/VNT/IMG_5248.jpg
This Audi vnt turbo uses the same rear housing as my turbo delopments vnt aswell there are a couple of pics of my turbo developments vnt in my profile albums and more pics of the VNT I have converted and other VNT diagrams
Jimmy_GTT
12-09-2010, 09:05
Thanks James.
And how much boost can you set up safely on such a turbo?
Thanks James.
And how much boost can you set up safely on such a turbo?
That question I unfortunately don't know. I currently run a turbo developments vnt and run 20psi manifold without any problems I have in the past run 24psi manifold without fault with the vnt. To be honest I am not to sure how much boost they can take and run safely with the abuse mine takes I would say a fair amount more is possible.
James, How do you find the gearbox copes? I remember when I had a VNT and was only running 1bar it felt like it was putting a lot of strain on the gearbox low down?
I've put a few pics in HERE (http://www.rtoc.org/boards/album.php?albumid=1166) of my old VNT and what I needed to do to modify it, wasnt a big job really, just drilling and tapping a few new holes.
Jimmy_GTT
12-09-2010, 14:39
I've put a few pics in HERE (http://www.rtoc.org/boards/album.php?albumid=1166) of my old VNT and what I needed to do to modify it, wasnt a big job really, just drilling and tapping a few new holes.
That is what necessary to rotate the housing?
What was your experiences with the VNT?
That is what necessary to rotate the housing?
What was your experiences with the VNT?
Yeah you just take the back end to bits and drill & tap 3 M4 holes, bolt it back together and jobs a good un :)
It was a good unit, made good boost low down and pulled well high up... I just didn't want to turn the boost up higher as I thought it would be a gearbox killer plus the 5 I had with the VNT wasn't built to set the land speed record.
Yeah you just take the back end to bits and drill & tap 3 M4 holes, bolt it back together and jobs a good un :)
It was a good unit, made good boost low down and pulled well high up... I just didn't want to turn the boost up higher as I thought it would be a gearbox killer plus the 5 I had with the VNT wasn't built to set the land speed record.
I was quite lucky with mine I didn't have to do any drilling or tapping mine was simply a Cade if moving the vane control ring around so the housings could sit correctly and the vanes be controlled properly.
As per Nial's comments I do fear for the gearbox I am using not as much as I worry about the piston rings I have in place.
allanr5gtt
12-09-2010, 16:42
what would it be like to have vnt and efi? could it be mapped using a vnt turbo?
what would it be like to have vnt and efi? could it be mapped using a vnt turbo?
Not sure about on efi engine but os8472 did have a vnt on an efi c1j also andy Cooke would be a good person to ask aswell
what would it be like to have vnt and efi? could it be mapped using a vnt turbo?
it is possible to have efi and a vnt but its a pain in the arse to get it working right, once you've got the basics sorted, the main problem being the boost control because some reason VNT's spike like mad when run on a efi engine.
Once thats sorted mapping is prefectly possible, Dave at Emerald had no trouble with that on mine.
Jimmy_GTT
12-09-2010, 21:20
it is possible to have efi and a vnt but its a pain in the arse to get it working right, once you've got the basics sorted, the main problem being the boost control because some reason VNT's spike like mad when run on a efi engine.
Once thats sorted mapping is prefectly possible, Dave at Emerald had no trouble with that on mine.
How could you sort spiking?
On how much boost have you used it? What power could it produce?
ive got a vnt on mine, currently running 16-17 psi. its an awesome turbo but it does suffer abit from spiking on the boost but when you can have boost from 1500-6000 rpm then you can live with it lol.
i think the only way around the spiking is by using an external waste gate to control the spike
Jimmy_GTT
12-09-2010, 21:37
Maybe a stupid question, but is the car more powerfull with VNT@16psi than with a T2/T25 hybrid @16psi ?
How could you sort spiking?
On how much boost have you used it? What power could it produce?
I used an external wastegate and that held the boost perfectly, so perfectly infact i'll never bother with an internally gated turbo again.
Power wise at a bar mine was making about 8bhp and 12ft lb top end but loads more across the whole rev range, did 40mpg and started so much easier.
I'll be honest if i had the money to do it again I wouldn't as its so much hassle getting the vnt and efi working together, thats not to say its impossible, just harder and more exspensive.
I'd love to see someone do it but unless you've got alot of cash to throw at it aswell as time and more than just a basic understanding of how engines work I say just get a decent T28, yeah you'll have more lag but it'll make more power, be more reliable and alot cheaper to build and get working
Maybe a stupid question, but is the car more powerfull with VNT@16psi than with a T2/T25 hybrid @16psi ?
Definatly @16psi manifold on the vnt at track n road in Essex a few years back I made 197.7bhp
At present I am running 20psi manifold with a 1 psi spike which is nothing really
Definatly @16psi manifold on the vnt at track n road in Essex a few years back I made 197.7bhp
At present I am running 20psi manifold with a 1 psi spike which is nothing really
i think i need to see your set up on the vains and actuator james. mines currently holding 17psi but spikes to 20psi
Alastair
13-09-2010, 06:09
I have been thinking about an engine re-vamp for the rally car, as out of low speed corners i sometimes struggle with lag (t28 and 285) unless you rev the knackers out of the C1J in first to keep the boostings up, or keep your boot on the gas and left foot brake which puts a huge strain on the clutch and drivetrain.
VNT sounds like a really good solution for this, what rpm can you need to get a bar of boost at? 2k?
I take it they are a lot less laggy than a standard type turbo, but how are they to actually drive?
Is adding EFI while your at it going to be worthwhile or a lot of expense for little gain?
Jimmy_GTT
13-09-2010, 07:08
Definatly @16psi manifold on the vnt at track n road in Essex a few years back I made 197.7bhp
At present I am running 20psi manifold with a 1 psi spike which is nothing really
But such power can be achieved with a T25 maybe on a little higher boost?
In this comparsion the low rpm torque will be much different?
Do you have a power curve about your car?
But such power can be achieved with a T25 maybe on a little higher boost?
In this comparsion the low rpm torque will be much different?
Do you have a power curve about your car?
I am trying to find the rolling road printout for an RTOC event I attend with 5teveL a few years back and a few other RTOC peeps back on the 29th March 2008. I will consintrate on mine and steve's cars as Steve was running full T25 and I was running the VNT both cars modified and unfortunatly both cars developed problems on the rollers mine was overfueling (MSM large Venturi carb) and bad water injection problems damping my spark to much causing huge spikes and Steve's 5 developed a bad misfire high up the rpm range.
Me running a VNT -
James-GTT-Modded---------------197bhp/207lbft (24psi spike down to 16psi, revved to 7800rpms only stopped revving due to problems:eek::scared: )
Steve running an Adam L full T25 (Bushy spec)
Steve-GTT-modded--------- 194bhp/190lbft (19psi boost, misfire at 5700rpms)
This is Steve's rolling road printout i will try and find a copy of mine.
http://i70.photobucket.com/albums/i96/24175mypics2/IMG-1.jpg
Jimmy_GTT
13-09-2010, 09:49
Thanks James5.
The best would be to 'taste' both cars.
I do not know if the VNT worth the time and the money to fit it, set it up correctly. Or easier (cheaper) solution would be a similar T25 from AdamL.
That will be a hard decision. ;)
The missfire top end was my headgasket on it's way out.....
T25 was a good spec for my last set up, I have a T28 now, I am waiting to see how it performs on a better engine ;)
Thanks James5.
The best would be to 'taste' both cars.
I do not know if the VNT worth the time and the money to fit it, set it up correctly. Or easier (cheaper) solution would be a similar T25 from AdamL.
That will be a hard decision. ;)
For pretty much plug and play the T25 that Steve had did a very good job and if i didn't have the VNT I would have gone that route.
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