Next 911 Turbo to feature Variable Turbine Geometry
November 16 of this year marked the day a century ago that Dr. Alfred Buchi received the first patent for an exhaust gas turbocharger. Porsche will be celebrating the turbo's 100-year anniversary a little late when it introduces the next 911 Turbo sometime next year with Variable Turbine Geometry. This technology allows the angle of the compressor's turbine blades to continually adjust. While some diesel engines have enjoyed this technology since the Nineties, the higher exhaust gas temperatures created by gasoline engines necessitated the creation of new heat-resistant materials to handle the hotness. Porsche and Borg Warner Turbo Systems were able to overcome the heat issue and have developed a VTG turbo system that will be incorporated into the next 911 Turbo. The VTG turbo will allow Porsche's flat-six to mimic a twin-turbo setup with a much broader torque curve and more flexible powerband than a standard single turbo could provide on its own. Power ratings for the new VTG turbo engine haven't been released and probably won't be until the new 911 Turbo surfaces sometime next year.
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Reader Comments (Page 1 of 1)
Ken 11:07PM (12/18/2005)
Bit unrelated, but a few weeks ago, there was a fleet of semi-camo 997TT's (5 I think) followed by a Cayenne Turbo (all with Georgia plates) testing in Reno, NV. Wonder if there are still some big things to be changed, or it is just refinement.
It was sure cool to see!
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Joe Weinstein 11:07PM (12/18/2005)
The article is a bit confusing, about
'mimicking a twin turbo'... The 996tt
is a twin turbo. Are they saying the
997tt will be a single-turbo?
I believe that variable-vane technology
is beneficial independently of how many
turbos are being used, so the 997tt could
have two VVT turbos. If the long exhaust
travel isn't a problem, maybe Porsche
could go to a one-turbo setup again...
Joe
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Chris 11:07PM (12/18/2005)
Joe/#5
I think they may have meant to say "sequential turbo" instead of twin-turbo. Sequential turbos are fairly well known for having little lag, and a VTS should definitely show the same characteristics.
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Liam 11:07PM (12/18/2005)
Variable vane has been tried before. Hopefully, they have it down now. In theory, the closed vanes spool the turbo up quickly (the high drag imparting thrust to the impeller), while the open vanes provide high boost. For a turbo, this is the best of both worlds. Others have tried dual turbos (most notably Maserati) to achieve high boost with a quick spool-up. Without VVT (variable vane technology, not the more well-known variable valve timing) engineers must balance between the two extremes, providing a turbo with a fair amount of boost that does not bog at low RPM.
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Pete 11:07PM (12/18/2005)
Seems a bit pointless given how lag free the Porsche Twin Turbos are already.
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Lucas 11:07PM (12/18/2005)
Cummins (desiel engines) has been doing this for a while. They see increased low end effeciency, no lag, and controlled high speed boost. If you look close at the picture, you can see the variable geometry blades. The are totally different from conventional blades.
They are indeed saying the 997 turbo will have a single turbo charger. The reason Porsche uses two turbos is lag. The smaller the turbo, the lower the rotor inertia. Thus two small turbos spool up quickly. One large turbo spools up slowly. The late 70's early 80's 930 comes to mind-- the last single turbo 911. BIGGGGG turbo that came on like a switch. Ive read stories about race drivers plating the gas pedal on the floor before they finished braking so they have power at the turn's exit.
As for sequential turbos -- no one has tried that gig since the 3rd generation RX-7. That thing had 70+ vacuum lines to control the two turbos and was famous for cooking the high speed turbo.
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Craig 11:07PM (12/18/2005)
Subaru used sequential turbos from 1993 to 2003 on the GT Legacy
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Andrew Brilliant 11:07PM (12/18/2005)
It is definately not pointless! It allows them to utilize a much larger turbocharger without sacraficing lag. If you make the compromises better you can add more on the power side of things and maintain the same driveability. A very minor turbo upgrade on a 996 can bring 100+hp out of the machine easily. Also decreasing the backpressure means more combustion efficiency in turn to a higher knock threshold. This allows for llowing more boost or higher static compression increasing off boost power or peak power depending on which route you choose. The benefits are huge! I would love to see this in a production car and this turbo technology will make its way down to enthusiasts everywhere!
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Henri 11:07PM (12/18/2005)
This is common technology for diesel, but was not feasible and reliable on gasoline engines, where gas temperature exceed 1000C (1900F).
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jason 11:07PM (12/18/2005)
Didn't Dodge do this a while back with their Daytona's, around 1990'ish. I seem to remember that those things died a fairly spectacular death, with lawsuits galore aflyin'....
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Karl Brauer 11:07PM (12/18/2005)
The technology was called "VNT" for "variable nozzle turbo" and while it didn't go over well in terms of sales or consumer awareness, it worked REALLY well. I had a 1989 Dodge Shadow CSX (1 of 500 made) with this engine (a 2.2-liter, intercooled 4 cylinder with the variable nozzle turbo) and it remains the most lag-free turbo car I've ever driven. Plus, it was good for beating up on 1985-1993 Mustang GTs and IROC-Zs. They weren't too thrilled whenever a 4 cyl, front-wheel drive Dodge economy car blew them away...(hee-hee) I can only assume Porsche will make the techonolgy work even better than the late-1980s Chrysler Corp. did, so it should be awesome.
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nonobeez 11:07PM (12/18/2005)
Hey, I had one of those VNT turbos!!! Aquired at Garrett in LA. They (smart engineers) stored the leftover stock from a cancelled order in the rafters. I pulled a couple for "testing"
I recall the problem Chrysler had was controlling the turbo correctly. Seems too much boost was created and it blew the headgaskets. Problem was solved (late) by dropping the efficiency by increasing the turbine to housing clearances.
Sold my turbo to a mopar gearhead that had an original Lebaron convertible VNT... talk about sleeper!!!
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