Oak

kevin, maybe I didn't read the link correctly but I didn't recall it mentioning in detail what and how the vanes are made to function. is this how the new porsche turbos will made?

even though slight and not as drastic as the turbo vanes you mentioned you don't think as the turbos spool up from static state to full spool there is absolutly no deflection with conventional vanes?

Kevin

Oak;

I believe what you are mentioning is a harmonic frequency or vibration.. This is not good in any turbocharger or jet turbine.. That is why it is very important to balance any vibration out of the rotating assy. If harmonics are induced, the turbocharger will destroy itself.. A compressor wheel that is overspun will burst.. Not a good situation at 155-175,000 RPM..

Oak

no, I'm talking about the deflection of the vanes with air pressure off the edges and ends of the vanes. you don't think there is any? from what I understand, most vanes are engineered with some type of ability to deflect and vary.

Kevin

There is thermal expansion of the inconel turbine blades.. And a minor amount on the compressor side. However, in practice the blades are suppose to remain rigid.

Oak

so, am I correct to say to some degree there is some variance?

Mongoose

In an axial flow compressor (modern turbojet engines) the compressor blades are like little wings - cantilevered from the center shaft mounting point. These can and do "flex" to a certain degree, as well as lengthen under the high temperature environment.

In a centrifugal flow compressor (1st generation turbojet engines - and ALL turbocharged automobiles), the compressor blades are integrated into a disk (blisk - blades and disk) and are much "beefier" as they have to turn the air flow 90 degrees while compressing it. The entire blisk might grow with increasing temperature, but I am fairly sure that it doesn't flex to any measureable degree.

Heres a link to a picture of a combination axial-centrifugal turbine wheel.

http://www.ent.ohiou.edu/~me321/quiz...compressor.jpg

Axial flow portion on the left, centrifugal portion on the right.

So to answer the question, no there is no detectable "flex" in an automobile's turbine blades (blisk).

Cheers,
Jason

Red rooster

Variable geometry turbos are well established technology in the turbo diesel field. Audi use them on the six cylinder TDi.Boost control is acheived by varying A/R .No wastegate needed. Benifits include faster spoolup as
you have a variable size turbo.
It was only a matter of time before someone cracked the problems, so these wonder turbos could be applied to gas motors.This technology is definitely NOT hype as I think you will discover.

Geoff

Kevin

This technology has been applied int he '80's I believe it was the Chrysler Daytona, and Shelby that had the variable vane Garrett's. They proved to be a service nightmare due to carbon buildup.

Oak

so, in real world operation there is some variance. measurable? well I guess it depends on what and how much you measure with, I would think also the size of the turbo will also depend on vairiations. my point was that there is some variations with all turbos measurable or not. in the real world not in theory.

it will be interesting to see if porsche does infact use this is the exact technology and material as been mentioned in this thread. as far as it making any real subtanitial difference in HP/torque and still being effective for mass consumption. hype? well that's still to be determined.

Red rooster

Oak,
The idea is that the turbo has another set of really variable , static vanes that allow the turbo to be geared up or down depending on available exhaust gas energy.
This means Much better operation at low rpm ,much less lag, as well as being able to make big boost further up.
In the turbo world this has been a bit of a holy grail !!!!
I am keeping my fingures crossed that Porsche have got this right and that 06 Corvette will be history !!!!!!!!!
All the best

Geoff

Oak

geoff, I get the idea of the variable vanes, would be surprised to see them on the 997tt. And if they truly are variable type, to what extent and what type of materials would be used. have to wait and see.

Kevin

I have seen the prototype test units. With modern Bosch programming the ECU will sweep the vanes similar to a fighter jet's engine before take off, you can see the nozzles moving.. Same basic function. The material will be inconel, good for 1650-2000F.

Oak

I'm still skeptical about the success of the inconel variable turbos in a high mass production setting, having done some cnc milling and programming for some inconel parts it is one of the most difficult alloys to machine. most inconel materials have been reserved for F1 or NASA and have been difficult to produce for one-offs let alone mass production. the stuff is amazing for resisting intensive heat.

porsche may produce them at a very high cost , could have some issues with reliablilty. all this at a huge performance gain? the numbers I'vs seen don't support this cost to power ratio.

Kevin

Oak were do you get your information? The turbine wheels in your car are made of inconel. I just received some inconel valves for a Porsche engine this week. The vanes are cast. Porsche isn't making the turbochargers. KKK is manufacturing them. Borg Warner, KKK, and Garrett have been making these units for sometime now.

Oak

kevin. are the new variable vanes cast or milled? I would think the variables would have to be machined from stock rather than cast. how is the pitch on the trubines vary? are they mechanically driven to be vary? it would seem that cast methods would not hold up to repeated close tolerances if they are mechanically driven to vary.