Jump to content
The mkiv Supra Owners Club

Varable Vane / Valve Turbos - Good for Us?


Dragonball
 Share

Recommended Posts

I wonder if this will be interest to us in the future?

 

Whilst prevalent with some Diesel applications and tried in the US some time ago - I understand the temps from petrol engines were considered too high...looks like Porsche have cracked it...!

 

"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."

 

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

Link to comment
Share on other sites

I've read up on these, they look like they are the holy grail when it comes to larger turbo's, helping with the spool up..

 

The only catch, due to involved machining and components.... costs are high, however they will start dropping...

 

Be interested to see how the developments go with this.

Link to comment
Share on other sites

There is already a skyline running around with these VNT turbo's on it, and preliminary results look rather interesting!

A mate of mine who owns a turbo company said "they are the way forward for sure"....;)

 

It goes back to the old style setup of 360 degree bearings etc but a lot more techy obviously.

Link to comment
Share on other sites

The only issue I would see with fitting something of this nature to a car.. would be controlling it...

 

Due to the fact that it is variable means that some sort of electronics will need to be used, and then comes all the fun of either having it in a fixed map style, eg 10% at 2000RPM or so on...

 

The obvious better solution is put something in based on throttle position, but then mapping could be an issue. For the non-vvti guys, I'm pretty sure one of the spare AEM outputs could be used for something like this, but mapping it will be a challenge...

Link to comment
Share on other sites

The only issue I would see with fitting something of this nature to a car.. would be controlling it...

 

Due to the fact that it is variable means that some sort of electronics will need to be used, and then comes all the fun of either having it in a fixed map style, eg 10% at 2000RPM or so on...

 

The obvious better solution is put something in based on throttle position, but then mapping could be an issue. For the non-vvti guys, I'm pretty sure one of the spare AEM outputs could be used for something like this, but mapping it will be a challenge...

 

I wonder if they could come up with a self-controlled unit? Perhaps it would monitor the exhaust gasses entering towards the impellor and adjust itself to suit. That'd be nice.

Link to comment
Share on other sites

A couple of ideas....

 

Use plenty of heat wrap on the exhaust, to keep the scavenging of heat under control... Using an EGT gauge close to the tubbie should allow you keep an eye on it....

 

For the controller, perhaps monitor boost pressure / TP and use it to control the vanes, again all speculation....

 

Also the newer designs I assume will use a more tightly controlled manufacturing process which should allow a slighter higher heat tolerance.

 

Hmmm, wonder if something like a megasquirt ECU, might be useful, being a small standalone cheap ECU, might be able to link it into sensors and then use it to control the vanes......

Link to comment
Share on other sites

These VGT turbo's on the 911 are going to be uber expensive units using the best materials...ie Inconnel etc. And they should be on a £100k car.

 

I don't think the control is a tough nut to crack...any decent standalone should do it.

Link to comment
Share on other sites

I think you could control a VNT turbo from any output map on an ECU that has output maps. It'll probably be a duty-cycle solenoid rather than a stepper motor and you can control those from spare injector maps. That means you can map your duty against boost pressure and RPM. It probably means you can only choose one boost pressure setting in the map though as controlling the vanes is how you limit boost but you'd get the mother of all spoolup times :)

 

-Ian

Link to comment
Share on other sites

I used to work on the engine calibration for diesel engines fitted with thesae VNT/VGT turbos at Ford.

 

The control system is based on a closed loop boost demand. There is an open loop duty cycle dwemand based on fuelling quantity and rpm (with many various modification maps such as temperatures, ambient pressure etc) that is close-sh to the required boost. This s then modified by a closed loop PID control system that achieves the actual boost within milliseconds.

 

Its fecking complicated, believe me!! But if you want a variable boost for different engine speeds & loads its the way to go.

 

Otherwise just fit a boost capsule that opens the vanes up when the target boost is reached. This will mean that at idle the vanes are closed and the turbo(s) can actually produce boost!!

 

The new Focus TDCI that the Mrs has bought has one of these. GT15 based I believe...... Hmmmm two fitted to a supe, with the boost capsule off the std turbos & the std boost control system fitted with an aftermarket controller?????

 

I could have got my hands on some (lots i.e. 50) prototype Transit 135hp VNT turbos that would have mated up to a standard Garrett flange.... but I didn't know I was going to have a Supe then. Doh :rolleyes:

Link to comment
Share on other sites

Yup, at the moment these seems to be the biggest step forward in turbo technology for a long while. I had a lot of fun with a Garrett VNT unit back in 2003 working on a 4 cyl 16v superbike engine design and development project!! Very very interesting to get into and spent months working on the whole setup (inconel manifold, custom grind cams, gears, dry sump, one off designed forged pistons to our spec, water injection, etc etc)

 

Anyway back on track ... Lots of power, plenty of boost just off idle, pulled like a train, never broke...a real beauty.

 

The powertrain never stayed with me personally but when I handed the project over we were having zero problems (temperature, control, reliability, mapping or otherwise).

 

I did try to hunt down a setup for the Supra but concluded (at the time, given what was on the market) that I would need three of the little buggers to make any worthwhile power.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. You might also be interested in our Guidelines, Privacy Policy and Terms of Use.