Turbo swap.

Is it possable to use a VVT turbo on a car that has a FVT turbo.

What are those? Check your terminology...

In general, the VW 1.9 TDI has either a GT15 (wastegate type) or a VNT15 (variable geometry). Changing between them is not straightforward, as they are not controlled in the same way. Not saying it can't be done, but there's more to the job than just the turbo.

Brian P.
'96 Passat TDI

Brian, I beg to differ. In reading one of those articles that Fred keeps in the archives (Allard Engineering) I understand that converting a GT5 turbo to a GTVNT turbo is a matter of changing the turbo/manifold and getting the plumbing straight. The same control for the wastegate will work for actuating the VNT adjuster. However, I have not done this to my car nor do I know of anyone, personally, who's done this so it is a 'buyer beware' situation.

I believe that both types are vacuum controlled, so it should be as simple a matter as hooking up the plumbing and fiddling with the VNT adjustment screw. But don't quote me on that.

Rattler: I assmune you're talking about the new VNT-15 turbochargers and the older wastegate-type GT-15s. (Actually, they're both GT-series turbos. But we all call the GT-VNT-15 turbo a "VNT" for simplicity's sake.)

-mickey

The GT15 wastegate controller is actuated by the POSITIVE boost pressure, not by vacuum. Follow the hoses: Red hose (positive boost pressure straight off the compressor) to boost pressure solenoid, to blue hose, to wastegate. The black hose from the boost solenoid is a vent to atmospheric pressure at the airbox. There is no connection to the vacuum pump anywhere in the turbo control system.

This is the same way that most wastegate-type turbochargers operate. Increasing boost pressure tends to actuate the wastegate open further, thus counteracting the increasing boost pressure.

As for whether the VNT uses positive boost pressure to open up the vanes, or vacuum, that I don't know. Someone care to open the hood and follow the hoses around the engine compartment?

Even if it does use vacuum, there's probably still some way to do it. What we don't know is how the ECU will react to the different behavior of the newer-style turbo.

Brian P.
'96 Passat TDI

Peter right about Allard, they just moved the vacuum across, but they had to make up a custom boost chip, as the original one would have killed the engine if it’s values had been used.