Just wondering if this type of turbo currently being used in the upcoming Porsche 997 911 Turbo , could be used in the RX8 .

In the May 2006 Wheels magazine on page 53 it says that these type of turbos were previously used only on diesel engines. The VGT system has vaines on it's turbine that open outwards to improve response at low revs, and close at high engine speeds to keep it spinning. From fully open to closed or visa-versa takes 100 milliseconds and the effect is like combining a small, low-inertia turbocharger and a big high boost one together in one unit.

http://www.autoblog.com/2005/11/27/n...bine-geometry/

Could this type of Turbo solve the current turbo problems of lag ??

Daniel

 

more importantly, its the first turbo for street use that was actually designed for 1700 - 1800 deg exhaust temps... you know, like our temps

 

I wonder what Scott could do with such a turbo....

5psi = 300whp....I'm still in shock over this....lol.

 

Very interesting technology, but the beauty of a turbo was the simplicity of it as compared to a supercharger. I believe the extra "brains" required to control the "variable geometry" is going to make it a lot less appealing.

Andrew

 

I had read something similar in that VATN turbos were only useable on diesels and not petrols due to the exhaust temps. Dual-scrolls are mechanically simpler and work with the petrol temps.

For a more in-depth, and propagandic, description of VATNs there's always Corky Bell's book on turbocharging.

 

Not sure where you are getting this info but regular turbos have running the boost & temps like this for years. Porsches have several aftermarket companies that run several different types of turbos at 1.2 Bar (what the new VGT's run) or even higher 1.3/1.4 Bar consistently. The innovation has to do with the design of this turbo. They did not get the variable geometry part figured out until recently. The vanes are a different design from a standard turbo. That was what needed a new design/concept and how to run this metal need to be different because it was a thinner, different design from standard turbos. Greddy & HKS have had massive turbos running 30+ psi on various cars for years, with high/higher heat points as well.

 

Dan, when u sayfix the "lag" problem, are u referring specificaly to our cars? B/c as far as I'm concerned, this greddy turbo is so small there is virtually no lag. Of course, the porsche turbo is undoubtedly a much better product, I just don't see it providing any advantage in throttle resposnse, at least in the 8's case.

 

Regular turbos are fixed though, so they don't have to worry about extra mechanisms inside breaking...

These turbos aren't all that new... I have a book from '02 or so talking about them. But yes, until fairly recently, these couldn't be used in normal gas cars because of the mechanism controlling the vanes would burn up. Now they have materials or whatever that can withstand the higher EGT of petrol cars.

As far as usability in the Renesis? I don't know... They are supposed to be fairly succeptable to high temps, which rotaries are known for. Maybe the materials haven't advanced that much?

It would be the ideal combination though. Especially for an engine with such a wide range of operating conditions.

 

Correct, they have had these VG turbos in diesels for about a decade. Regular turbos have been running these temps (and more) for a long time now.

 

I had an AeroDyne VATN on my Miata for a while. It was nice, but fragile.
The "brains" for operating the vanes are no more complicated than a wastegate. In fact, the VATN didn't need a wastegate because the variable geometery took care of that as well. Sizing was tricky, but it worked well.
Until it broke.
The self-lubing bearings are a weak point and since they are walking such a tightrope to keep the thing balanced, any overspeed at all destroys them.

 

there's a difference between variable vane geometry (ford powerstrokes),
and variable turbine geometry.

porsche has seen over 1000*c during testing on their piston engines, so i don't even wanna know what the rotary version of that heat would do. i've looked into buying one of these turbos, but can't find any for sale.

 

Porsche / Borgn Wagner Jointly worked on the 997 turbo , so maybe contact them but i would hate to hear of the cost of one .

 

Lag was possibly the wrong word

But the VGT having both low end power and high end power boost , and being able to handle high temperatures seems attractive

As previously stated

The VGT system has vaines on it's turbine that open outwards to improve response at low revs, and close at high engine speeds to keep it spinning.

From fully open to closed or visa-versa takes 100 milliseconds and the effect is like combining a small, low-inertia turbocharger and a big high boost one together in one unit.

Minimum boost for maximun power

 

garrett and holset both have their versions of the same thing too. but i still can't get ahold of any of them. holset told me to talk to their dealers. the dealers won't respond.

 

Sounds attractive, but I'm sure the pricing would not.

 

i've been emailing back and forth with holset and one of its distributors about this.

turns out, the actuator is either electric, or pressure-actuated (like a wastegate actuator). the problem is:

1) finding an ems that can control an electric actuator.

2) if it's a pressure actuator that's used, they operate at 100-150 psi, so you'd need to install an air compressor in the car just for the turbo actuator.

 

All this is very cool, but to build it into an RX-8 couldn't be cheap. At this point, I think I'd just go ball bearing, accept the slight lag, and be thankful for the simplicity and extra power that I didn't have before.

 

not just the rx8... the turbo itself, with no control unit is $2-3k+, depending on the size.

 

We just need variable geometry rotors and housings!

 

 

hell they have variable geometry penises available today...who knows what tomorrow will bring??

btw, i've been looking into the vtg thing for a while now as a potential pj for my fd. i'll let you know the exact price and post up a compressor map when i find out how much that exact unit is.

 

If I told you what my latest rotary project idea is, you'd think I was crazy. I never have the time to get around to trying most of my ideas anyways.

 

STORY TIME!!!!!!!!!!!!!! please tell us, papa!!!!!!

 

just face it, you're an engineer at heart

 

I'm not even sure where to start on it other than to just try something and hope the engine doesn't blow up (which it may!). Until I work out the feasibility of what I'm trying to do, I don't want to divulge too much. It's controversial at best but it has been made to work by others. Too bad it's only been on test benches and for non automotive related projects. It's not any form of new technology though and it won't help you with a Renesis so don't get too excited. It's really just a personal project that no one really has anything to benefit from other than gaining a little knowledge and perhaps a couple of broken apex seals.