Mark Houghton

See below where I cut and pasted a quote from an article I read on the 2008 911 turbo Cabriolete. I know absolutely Zip about this technology. Could it be adapted to our 930's?

Using Variable Turbine Geometry (VTG), the powerplant generates 480 horsepower and 460 lb-ft of torque at 1950 rpm. The heart of the Variable Turbine Geometry technology is the turbocharger’s adjustable guide blades, which can vary in angle to most effectively guide engine exhaust flow onto the turbocharger’s impeller wheel. The result is a system that provides the advantages of both a small and large turbocharger, thus eliminating the turbo lag or old and, instead, offering unheard of flexibility and awesome acceleration, particularly at low engine speeds.

Matt O.

Think of it as a variable guide vane for a jet engine. That's almost exactly what it is. Basically varies the AOA on the turbine blades, by varying the relative wind, reducing turbo lag without decreasing the size of the turbo. At least that's my understanding. As far as adapting it to a 930... an uneducated guess is that would be a nightmare with not very noticable gains given the lim-fac is the CIS/engine...?

Matt O.

http://auto.howstuffworks.com/porsche-911-history47.htm

Mark Houghton

Sounds logically simple, based on centripetal force. The vanes must be either spring loaded (or made of spring steel), or hydraulically actuated somehow. Interesting....I still wonder if the application might be something worth going after, CIS limitations or not. Sooner boost is what we're all looking for.

911rudy

We had the same technology on the old F4 Phantom that I flew in the Marines. It allowed the engine to spool much quicker than a stock jet engine but there was a maintanence cost. There were several inputs to control the pitch angle but I believe we have the computers now to take care of that. I suspect the cost would be factor too. I would love for one of you to perfect it and then write about it here so we all can order one!!!

srf506

911rudy,

McDAC did a great job of engineering that old bird so we could fool it into thinking it was flying a whole lot faster than it was, and reducing the spool up. the T-37 I took basic jet in could take up to 14 secs to spool. You really had to be in front of the AC on that one. If you thought you needed power you started adding it. We could bleed the speed pretty quickly, but we couldn't ever allow ourselves to be behind the power curve.

If it doesn't require a million ECU inputs to control the Variable Vanes but uses either centripital force or oil pressure, than it might be adaptable if you had an FI conversion. I don't think I'd use it on CIS because you can't control the fuel enough.

kens911

they have been using these in diesels for several years now. it's pretty simple with only a couple moving parts. I think I saw it on trucks on tv a couple years back. I think it was garret but I dont remeber for sure

Matt O.

**** hot. My dad flew F-4s in the '80s. Just had my last 38 ride yesterday.

nathanUK '81 930 G50

I don't see any reason at all why it couldn't be made for us and it would work well, even with CIS as boost is boost. Of course 930's are an expensive hobby though

jetskied

The real question is that will a variable vane actually have any real world benefit for a 930. Remember that a 997 has two small turbo thus they are already easy to get on boost. Not to mention that they have higher compression and are a larger displacement which only helps get on boost quicker. A HF turbione works pretty well, I just don't know if the VV turbione will have any real benefits.

911rudy

If it works the same way as on the jet engine it should help getting the turbine up to speed much quicker. Since the pitch on the turbine wheel is much less at low rpm it takes much less exhaust pressure to spin it up. However, even though it is spinning at a high rpm it is not putting out any boost due to the low pitch angle. The question is whether or not, as the blades increase pitch angle, will the useful amount of boost come in quicker. I think it will. BTW srf506 we used to have to plan ahead on when the boost or thrust would come in on the old jet engines just like we all do with the 930's. Some times we misjudged and bad things would happen. Sound familar?

DonE

I think a VGT would work well on an EFI converted 930. Changing the geometry of the blades depends on throttle position, engine load (MP) and RPM. Based on these parameters, you need a motor (solenoid) driven by a computer to alter the vanes. Since you can't alter fuel by either throttle position or manifold pressure on a CIS car, this technology is not feasible for CIS.

I like it on my powerstroke 6.0L, but there is a maintenance factor on higher mileage or city driven motors. The soot from the diesel can clog the vanes and prevent the actuator from working, so there is a published procedure to dismantle, clean and reassemble. Otherwise, its cool...

nathanUK '81 930 G50

I suppose a small ecu to do that and a tps is half way there to going efi. But it could be done.

srf506

911rudy,
Oh yeah, sometimes I really had that "sinking feeling" if I got behind the Phantom. Then when the engines finally spooled it was "eyeballs in." There were times you weren't real sure where you were going, you just knew you were getting there really quick! As Phil Hartmann always said "Good times!"

Now they're on "gate guard" duty on sticks or being used as drones for gosh sakes.

Cheers,
Jim P.
33 TFW (retired)

Kevin

I have been working on a variable vane turbine for the last 2 years.. While it was "not" my idea, I have been testing the unit on my test engine. The initial prototypes were built off my Hyflow and larger K27 turbine housing and turbine wheels. All in all, there is a very short window for which the vanes can work to accelerate the turbine wheel. The control system is the key, for making it or breaking it.