Varible vane Turbo

[pgarner]

Ok this was touched upon in Skoda VRS have you driven one.
most diesels have variable vanes to adjust boost.

ok what im really looking is more info on these. how do the vanes change their angle to increase pressure the bearing spins at high speed so i cant see how it easily they could be turned.
And why arent they used on petrol models ?

as was also touched by HDI in the above thread was that his Pug 406 has variable vaned Garrett turbo but it has a waste gate fitted to it as well. can anybody answer why this is as surly not required as the vanes could lie basically flat to get no boost and therefore no need for the wastegate.

the best answer i could come up with was as a safety device in case the vanes were to get jammed in a high boost setting. But surely if the engineers had spend millions on the engines they way have worked out how to get rid of this problem

Questions lots of questions so all you diesel heads see if you can answer any of these questions please

[Flori]

um,
try wikipedia? the german article is quite interesting and a bit longer then the english one. but both have links.

[pgarner]

flori never thought about using wiki for that
still found a little info on it

basically the variable vane turbos allow the turbo to maintain boost through more of the rev range than a conventional turbo

with regards to the wastegate issue. some VGT (variable geometry turbo) can overboost even when the vanes are set to their lowest limit. the vanes themselves are altered by an actuator.

and with regards to petrol engine it has been used with several.

• 1st used in '89 shelby 2.2
• '92 Pug 405 T16
• jeep cherokee with the 3 ltr merc engine can be found with one
• and most recently the '07 911 turbo

can anybody confirm this info ? as i know wikpedia isnt liked by all on this site

[HDi fun]

Wikipedia is OK - perhaps the clever part of using it is to be able to sort the wheat from the chaff.

[waynne]

It points you in the right direction. I'm thinking we should cover this in the main site so keep watching this space for an article. (Any more comments and pointers would be appreciated.)

[jarrus464]

varible vane turbos would be too expensive to produce in mass produced petrol engines
ok agruably the new 997 911 turbo could be called a mass produced car but it's an expensive and high performance sports car. they won't use them in cars like an Astra VXR or a Focus ST then the price of the car would have to be more..and when you buy a car like that your likly to spank it's balls anyways in the turbo rev range

this is because they have to be made out of more heat resistant meterials because of higher exhaust gas temps. (higher than diesels)

plus standard turbos take a little longer to spool up in diesels, my TD has has a non variable vane turbo and it's not on full boost till 3000k and i'll problebly change between
4-4.5k plus it's aids in the low end (before 2k) becasue older diesels with no tuning tend to be quite flat and then you get and almighty surge which can't be good for fuel economy ethier...

so with a variable vane turbo you can get some form of useable power right from 1500 rpm in new diesels so you change earlier and improve fuel ecomonmy plus you get better off the line "grunt"