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Discussion Starter #1
I am not allowed to say whose car it is other than its a 2.8 engined R33. The car makes 0.5 bar of boost @ 2050rpm and 1.2 bar @ 2500rpm and drives like a Jag V12. :bowdown1:
More info and pix to follow soon :cool:
 

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VNT stands for Variable Nozzle Technology..also called VGT (variable geometry technology). Diesels have been using them for 3-4 years as they are ideally suited to a low revving engine i.e the peak torque on the engines I work on is at 1750rpm and holds that peak boost right to the fuel cut off at 4800-5200
Petrol Exhaust Gas Temperature is a lot higher and its been a struggle to find a unit capable of withstanding it.
The latest Porka turbo I believe is the first production petrol car using VNT. I knew of a ren 5 turbo 4 years ago using one as the tuner asked me if I knew of the turbo and when I looked i noticed it was a ford prototype item that we used for development...
I get a lot of questions asked as part of my job about how they work so I took one apart and have a load of picture of a stripped turbo and how the vanes work...they are around somewhere so I will post them up...as...to be honest...I hasn't seen the innards meself..let me pack for me hols first and I'll put them up..unless someones beats me to it..
 

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has the Garrett electric-assist turbo made it past the concept/prototype stage?
 

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Discussion Starter #8
I couldnt find the post I made with these pix so here they are again







an electrically assisted turbo

 

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Philip said:
Not quite - this had one back in 1989:



Phil
Shelby CSX-VNT 1989 production run of 500 http://images.google.co.uk/imgres?imgurl=http://www.xmission.com/~dempsey/shelby/vntcvr.jpg&imgrefurl=http://www.xmission.com/~dempsey/shelby/sheldod9.htm&h=578&w=462&sz=78&hl=en&start=1&tbnid=zHBe_8lM9F2snM:&tbnh=134&tbnw=107&prev=/images?q=shelby+csx-vnt&svnum=10&hl=en&lr= .


VNT's have been about for a VERY long time with the first designed in the 1930's. Materials, reliability and cost have been the big factors stopping them making it into mainstream cars. Porsche is the first "mainstream" motor in a sense although IMHO it was the Shelby CSX-VNT but that will not stop the marketing men putting the spin on it - like Jason Plato in 5th Gear on Monday about the new Porker Turbo being the only 4WD drive car to let you hang the back end out - that's a laugh.
Don't EVER believe the hype ALWAYS check the facts yourself.
 

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Had some better pics but they are on my work PC...this is with the exhaust housing removed...first pic is in the closed position

And then with the vanes in the fully open position

Obviously, there is a normal vaned wheel inside there that the vanes direct the exhaust gas onto

The 'box' thing on the left is a 'REA' which is a Rotary Electronic actuator. The older ones control the vanes using pressure just like a 'normal' turbo. This one uses a stepper motor connected to a worm gear which then controls the black arm and swivels the vanes. As I understand it's this REA mechanism that couldn't handle the 900 deg petrol EGT's up to now reliably




 
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Biggest trouble with VNT turbo,s is heat , load sof cars use them but they run on that horrible stuff called Diesel ( well not always horrible just ask Audi) Porsche seem to have sorted it but like must things you pay for the knowledge ( Coming from Motorsport which invoved Porsche a few years ago) I saw on a dyno a Flat 6 giving way over 800bhp but giving boost from 1500rpm but teven then they said the turbo,s will only lasy approx 6000km due to the heat in the exhaust housings Diesels engines dont run excessive temps in exhaust housing.

The Porsche turbo is not available yet as a new part yet , but I have a customer that has a 33 GTR that is a engine designer at BMW thats has seen some drawings of some turbo,s with high spec exhaust housings incl VNT workings.

Yes everyone is trying them should be good once the manufactuers sort of the temp problems.
 

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Exciting stuff... can't wait to see how they perform on a RB26DETT;)
 

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I can't wait to see how much they cost :bawling: - remember some turbos used on older 911 model cost £4500 to replace!

EGT has always been the problem (diesel is a lot lower) and maybe even then the life time of the unit may be just outside the warranty mileage :mad: . If they do need rebuilt in the future it could be a costly one.
 

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No idea how much one that withstand 900+ deg EGT is going to cost but the ones we use that run 1.25 bar cost fudd (ok...large volume) a few hundred bucks.
I should do a search and have a look how porsche have done their latest unit. Porsche don't traditionally use Garrett/Honeywell...I'm guessing that the latest tubby uses KKK or maybe IHI units. Either way...its a close knit community...if one company is doing it then all the others won't be far behind. Tis all good for the rest of us!
 

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turboslippers said:
No idea how much one that withstand 900+ deg EGT is going to cost but the ones we use that run 1.25 bar cost fudd (ok...large volume) a few hundred bucks.
I should do a search and have a look how porsche have done their latest unit. Porsche don't traditionally use Garrett/Honeywell...I'm guessing that the latest tubby uses KKK or maybe IHI units. Either way...its a close knit community...if one company is doing it then all the others won't be far behind. Tis all good for the rest of us!
Porsche used to use KKK for racing stuff in the 70's and 80's according to my older AE books - see http://www.btinternet.com/~skyline6969/porsche.jpg it's an old engine and really BIG but the 936 was producing over 600hp from a 2.6 litre in the early 70's and racing endurance races with it!
 

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COSSYCam said:
........... and drives like a Jag V12. :bowdown1:
Does that mean it will catch fire ever few months? :flame: :flame: :rolleyes: ;)


There is only ~100DegC difference between a diesel and a petrol
engines exhaust temp. But that 100 degrees makes a difference.
 
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