VNT25 Turbos?

[Twisted6]

I am building a turbo motor and about everything I have decided except for which turbo(s) to use. It is going in a custom application, so packaging constraints are of no concern. I have always fancied the idea of twin turbo Yamaha. I am not looking for an extreme horsepower figure, rather going for something just fun to drive and sharp acceleration.

I stumbled across the Garrett VNT-25 turbo, Variable Nozzle Technology. Similar to the Variable Geometry Turbos that Porsche and others are using today, but the VNT is from the 1980s, used by Dodge on it's late-80s Shelby cars. It has no wastegate, uses a diaphragm that sources manifold vacuum and boost pressure to control the vanes, a manual boost controller can also be added to control when the vanes open and close.

Has anyone else considered using a pair of VNT25 turbos?

 

[somedude_001]

I had considered that on my SHO powered camaro project but I choose to go with a more conventional setup because my goals do not really include good driveabality. Correct me if I am wrong but VNT25's are actually pretty big are they not? You can get a very reliable 350whp out of a stock SHO engine you can definitely make more but 350 is a very safe number with proper fuling.

What is your project?

edit: I think a VNT setup would be amazing for a car driven on the street.

 

[Twisted6]

I had considered that on my SHO powered camaro project but I choose to go with a more conventional setup because my goals do not really include good driveabality. Correct me if I am wrong but VNT25's are actually pretty big are they not? You can get a very reliable 350whp out of a stock SHO engine you can definitely make more but 350 is a very safe number with proper fuling.

What is your project?

edit: I think a VNT setup would be amazing for a car driven on the street.

I cannot find a compressor map on this turbo and scanning the internet for swaps, from 300ZXs to Volvos to VWs. there is no general consensus as to it's 'size'. The person who swapped the VNT25s onto his 300ZX said they pulled hard, but didn't last long due to his high EGT destroying them. Which is another thing I cannot get any definite answer on, what temperature they are good up to.

Specs wise:

Compressor housing A/R: .48
Compressor wheel inducer: 40mm
Compressor wheel exducer: 52mm
Turbine housing A/R: .64
Turbine wheel inducer: 53mm
Turbine wheel exducer: 46mm

It is also water-cooled.

Project wise, I have a 94 Mazda B3000 that it is going in.

 

[Off Road SHO]

MMMMMMM....twin turbos







Tom (with only one spinny thing)

 

[somedude_001]

I cannot find a compressor map on this turbo and scanning the internet for swaps, from 300ZXs to Volvos to VWs. there is no general consensus as to it's 'size'. The person who swapped the VNT25s onto his 300ZX said they pulled hard, but didn't last long due to his high EGT destroying them. Which is another thing I cannot get any definite answer on, what temperature they are good up to.

Specs wise:

Compressor housing A/R: .48
Compressor wheel inducer: 40mm
Compressor wheel exducer: 52mm
Turbine housing A/R: .64
Turbine wheel inducer: 53mm
Turbine wheel exducer: 46mm

It is also water-cooled.

Project wise, I have a 94 Mazda B3000 that it is going in.

any idea what kind of power other guys are making with them? being a turbo I would think EGT's would not be so much of a issue unless it was a diesel engine. I would not worry about over heating a turbo any more than I would worry about melting a piston from a bad tune.

That should be a very cool project! what transmission are you using? Nick might have a spare adapter plate laying around if you are using a GM transmission.

 

[somedude_001]

can you find any dyno graphs on those cars using these turbos? you could probably get a decent guess based on that.

 

[Twisted6]

any idea what kind of power other guys are making with them? being a turbo I would think EGT's would not be so much of a issue unless it was a diesel engine. I would not worry about over heating a turbo any more than I would worry about melting a piston from a bad tune.

That should be a very cool project! what transmission are you using? Nick might have a spare adapter plate laying around if you are using a GM transmission.

Transmission is all about what money is available when it comes down to that time. It's going to be an automatic, since the truck is already that way. So I have a perfectly fine and relatively low-miles A4LD that can easily be converted over to full mechanical control, and even Frankentranny'ied with 4R/5R components.

Ultimately I would like to get an adapter plate and TCI's 6X transmission and TCU combo with paddle shifters.

 

[firebat45]

I considered it, but given how hard it is to find the turbos, and rebuild kits, decided against it. If you want a variable turbo, the HE351VGT is MUCH easier to come by, and will support tons of HP while not spooling ridiculously slow. Too big for twins though.

 

[somedude_001]

If you want twins non VNT I know you can pick up K04's new for under 2K and those would have instant throttle response and will be good for about 400whp maybe more IDK but I know a few friends local to me made high 3XXWHP on a AWD car. Just a thought.