Variable Turbochargers

[Preen59]

Here's a good article on the principal of operation for adjustable turbos.

http://members.ozemail.com.au/~avdw/pdf/Adjustable%20Turbocharger.pdf

Pinched from the Aussie Caddy Forum.

http://www.getphpbb.com/phpbb/index.php?mforum=dutchaussie

[cetane]

All is revealed!

So now I fully understand how it operates. Thanks, mate!
It's worryingly complex though as there's a hell of a lot of moving parts in a pretty hostile environment. Makes you wonder about reliability/longevity. In addition, there's even more sensors and computers to malfunction if you're unlucky, and of course you'd need VAGCOM to pinpoint a fault. I once swore that if I couldn't fix it myself I wouldn't buy it, but here I am driving around in a Mk5 TDI
Extended warranty is looking more appealing

[gldgti]

complexity

they are getting a name for jamming up.

its not hard to rig up a VNT in a car without any electronics though.

on a normal turbine, you use the boost pressure to operate a diaphragm controlling the wastegate. on the VNT, you simply use the same diaphragm to actuate the vane control, set up for restriced outlet at no boost and unrestricted as the boost builds.

there are an increasing number of guys putting VNT's on old 1.6TD's and AAZ (1.9TD) in the US. GTD forum has some info.